Evaluation of Playing Surface Characteristics of Various In-Filled Systems

Evaluation of playing surface characteristics of in-filled systems.
Evaluation of Playing Surface Characteristics of Various In-Filled Systems - Articles

Updated: November 10, 2016

In This Article
Evaluation of Playing Surface Characteristics of Various In-Filled Systems

by Andrew S. McNitt, The Pennsylvania State University
Dianne Petrunak, The Pennsylvania State University

Note:

First-time visitors to this site may want to start by reading "Summary and Considerations". Detailed information about a particular topic can then be found in the "Table of Contents" below.

Introduction and Objectives

Since synthetic turf was first installed in the Houston Astrodome in 1966, numerous studies have been conducted to evaluate the safety and playability of synthetic surfaces. These studies have included material tests on the traction and hardness of these surfaces (Valiant, 1990; Martin, 1990), human subject tests where an athlete performs various maneuvers on the surface (Cole et al., 1995; Nigg, 1997; Nigg and Segesser, 1988), and epidemiological studies that have counted athlete injuries on synthetic versus natural turfgrass (Powell and Schootman, 1992; Powell and Schootman, 1993).

Various methods have been developed to measure the playing surface quality of sports surfaces. For example, different methods of measuring playing surface hardness have been developed for synthetic turf versus natural turfgrass surfaces. For synthetic turf surfaces the U.S.A. standard is the F355 method (American Society for Testing and Materials, 2000a). For natural turfgrass the standard method is the Clegg Impact Soil Tester (CIST) (American Society for Testing and Materials, 2000b). Although both methods determine hardness by dropping a weighted accelerometer on the turf surface, some have stated that these two methods should not be correlated (Popke, 2002).

A new configuration of synthetic turf has been introduced into the market place. Termed 'infill' systems, these synthetic surfaces are comprised of a horizontal backing supporting numerous vertical nylon, polypropylene, or polyethylene fibers. These vertical fibers (pile) are much longer than those of traditional synthetic turf and can be filled with varying types of granulated material (infill media), typically sand or crumb rubber. It is believed that these new infill systems provide athletes with a surface that performs more like natural turfgrass than traditional synthetic turf (Popke, 2002).

As more synthetic turf systems using infill are introduced into the sports surface market, independent data regarding playing surface quality are required to enable consumers to make informed decisions.

Athlete Performance and Safety

A brief review of Athlete Performance and Safety of Infilled Synthetic Turf Systems.

Objectives

This study was designed to evaluate the playing surface quality of various infill systems over time. Surface quality will be periodically evaluated as the systems are exposed to weather and simulated foot traffic. The effects of various maintenance practices on the playing surface quality of these systems will also be evaluated.

Construction of Experimental Plot Area

In the fall of 2002, we prepared the sub-base for the installation of the infill systems.

The topsoil was stripped from the site and the subsoil was compacted (Fig 1).

A 4 in. layer of gravel (Fig. 2) was installed.

After the gravel was graded and compacted, a 0.75 in. layer of a fine gravel containing appreciable coarse sand (Fig. 3) was topdressed over the area

This allowed a more precise grade to be created (Fig. 4).

When the sub-base was complete, various companies marketing and installing infilled synthetic turf systems arrived at The Joeseph Valentine Turfgrass Research Facility at Penn State, and began installing their systems. Most installed nailers around the perimeter of their plots (Fig. 5).

Each product was installed in three 15 ft by 15 ft plots in random locations. All measurements and data reported in this document are the average of values obtained from the three locations (Fig. 6).

Some companies installed a shock-absorbing pad and some did not (Fig. 7). The three systems containing pads were: Astroplay, Nexturf, and Sofsport.

One company, Geoturf, installed an underlying grid that can be used to circulate heated or cooled air throughout the system (Fig. 8). No forced air circulation was done during this study but the effect of the underlying grid on playing surface characteristics was of interest.

Next, the backing with the upright fibers (pile) was attached to the nailers. (Fig. 9).

The infill material was then topdressed onto the plots using a traditional topdresser. (Fig. 10).

Infill materials varied. Some contained a mixture of sand and crumb rubber while some contained 100% crumb rubber (Fig. 11).

The crumb rubber was then worked into the pile using a power broom (Fig. 12). More infill was topdressed and power broomed. This process continued until the desired depth of infill was installed. The depth of the infill, for each product, is reported in Table 1.

Characterization of Infill Systems

The following are links to the specification sheets for the various products installed in the study.

Simulated Foot Traffic and Grooming

We began to impose simulated foot traffic during July of 2003. Traffic was applied using a Brinkman traffic simulator (Cockerham and Brinkman, 1989). The Brinkman Traffic Simulator weighs 410 kg and consists of a frame housing two 1.2-m long rollers (Fig. 12). Each roller has steel dowels or spriggs (12.7-mm diameter by 12.7-mm length) welded to the outside of the rollers, at an average of 150 dowels m-2. These dowels are the approximate length and width of the cleats on the shoe of an American football lineman at the collegiate level. The Brinkman Traffic Simulator produces wear, compaction, and lateral shear. The drive thrust yielding lateral shear is produced by different sprocket sizes turning the rollers at unequal speeds. The Brinkman Traffic Simulator was pulled with a model 4200VXD Ventrac tractor (Venture Products, Inc. Orrville, OH) equipped with a dual turf tire package.

Plots were split with two levels of traffic. The traffic levels were no wear, and high wear (eight passes three times per week). According to Cockerham and Brinkman (1989), two passes of the Brinkman Traffic Simulator produces the equivalent number of cleat dents created between the hash marks at the 40-yard line during one National Football League game. Thus, 24 passes per week are equivalent to the cleat dents sustained from 12 games per week.

Traffic began on 7 Jul 2003 and 21 April 2004. Typically, traffic was applied regardless of weather conditions or water content of the infill. Numerous traffic applications occurred when the plots were very wet. Occasionally, due to heavy precipitation or schedule conflicts, traffic was not applied on the scheduled day. In these cases, traffic was applied on the following day.

In order to collect data, traffic was not applied for an approximately 3-week period at the end of July through early August in 2003 and 2004. Traffic resumed in mid August of each year and continued until 9 Oct 2003 and 8 Nov 2004. Plots were groomed on 9 Oct 2003 and again on 4 Aug 2004. Grooming consisted of loosening the granules using a 40" Lawn aerator (model # 45-0296 Agri-fab, Inc. Sullivan, IL) shown in Fig. 13.

Two passes with the lawn aerator were applied on each half of each plot with the second pass being 90° to the first. Following loosening of the granules, the pile above the infill material was broomed using a hand held power broom (Fig. 14) to try to return the pile to an upright position. Data collection again occurred during the week after grooming was complete.

Surface Hardness (Gmax) Method

Surface hardness was measured using a CIST equipped with a 2.25 kg (5 lb) missile and a drop height of 455 mm (American Society for Testing and Materials, 2000b) and the F355 method equipped with a 9.1 kg (20 lb) missile and a drop height of 610 mm (American Society for Testing and Materials, 2000a) (Fig 15). Impact attenuation, as measured by an accelerometer mounted on the missiles, was used to indicate surface hardness and is reported as Gmax, which is the ratio of maximum negative acceleration on impact in units of gravities to the acceleration due to gravity. The average of six CIST and three F355 measurements taken in different locations on each subplot was used to represent the surface hardness of that subplot. A single F355 measurement consists of dropping the missile three times in the same location with a three minute interval between each drop. The value reported as Gmax is the average of the second and third drop in the same location. When using the CIST we report the Gmax value we obtained with the first drop on the surface. Measurements were taken when the surface was free of moisture from dew or precipitation.

The experimental design was a completely random split-plot statistical design with three replications. The split was wear and no wear. The means of the six CIST and three F355 measurements were analyzed using analysis of variance and Fisher's least significant difference test at the 0.05 level. A LSD was not calculated when the F ratio was not significant at the 0.05 level.

Results and Discussion

For all results in this section it should be noted that this data is from the first two years of a long term study and represent only that time frame. These results will be updated as more data is collected during subsequent years.

F355

The Gmax, Severity Index, and Head Injury Criteria (HIC) for data collected during 2003 and 2004 are shown in Table 1 and 1a. We found that Gmax had a high correlation with the severity index (0.97) and head injury criteria (0.96). For this reason, we are currently suggesting that Gmax should be the main focus when comparing surface hardness values.

Table 1. Colony forming units (CFU) detected on R2A media per gram of crumb rubber.
Treatment28-31 Jul 20038-12 Sep 2003
Gmax1HIC2SI3Sub temp (°F)4Infill depth (cm)GmaxHICSISub temp (°F)Infill depth (cm)
No Wear
Astroplay75.0173.5201.178.94.279.7183.8231.373.04.0
Astroturf113.3244.7293.182.20.7102.1244.0285.978.2NA
Experimental81.1182.2211.776.53.683.1195.9227.975.43.5
Fieldturf93.1203.4237.283.54.394.4223.1259.674.84.3
Geoturf101.6240.2282.596.62.8101.1234.7273.770.03.3
Nexturf62.1130.5152.574.72.370.2158.2184.580.92.2
Omnigrass 4183.3198.2229.783.44.087.7208.6241.969.23.9
Omnigrass 5172.5170.2196.578.14.995.0234.9272.671.14.9
Sofsport88.8204.6238.788.43.2105.0258.1305.672.73.3
Sprinturf101.9235.3276.079.22.6102.8236.7278.773.62.8
Wear5
Astroplay75.7174.0202.279.34.282.1196.5227.572.04.0
Astroturf109.6227.1274.181.90.7108.3258.9305.079.0NA
Experimental86.9207.2240.376.03.581.1190.1221.275.43.2
Fieldturf95.3214.2250.379.24.295.1225.5261.975.84.2
Geoturf95.4217.9254.588.73.1100.6239.7279.371.33.1
Nexturf64.8139.4164.175.02.268.7152.0177.687.31.8
Omnigrass 4189.0221.5256.782.73.893.2228.9264.969.23.7
Omnigrass 5178.3193.0222.882.14.890.9219.9255.371.74.6
Sofsport88.9209.8244.286.83.1103.8252.8299.772.63.1
Sprinturf106.6253.6296.778.12.599.2232.0273.173.22.7
LSD (p=0.05)6.124.128.04.50.38.029.233.82.50.2

1Surface hardness was measured according to ASTM standard F355.
2HIC = Head Injury Index
3SI = Severity Index
4Subsurface temperature was measured 0.5 inch below the pile backing.
5July testing performed after wear simulating 36 games. September testing performed after wear simulating 88 games.

Table 1a. Surface harness (Gmax), Head Injury Criterion (HIC), Severity Index (SI), and pad temperature of ten synthetic turf products
Treatment1-9 Jul 200410-25 Aug 2004
Gmax1HIC2SI3Sub. temp (°F)GmaxHICSISub. temp (°F)
No Wear
Astroplay79.4194.5225.275.278.9187.3216.870.4
Astroturf129.1307.8371.384.6129.7305.9376.677.9
Experimental80.4176.6204.679.287.6201.7234.376.5
Fieldturf97.7222.2258.682.097.3217.7253.377.6
Geoturf103.1254.6296.792.1105.8256.3299.179.1
Nexturf68.1156.1182.276.968.2151.8178.273.1
Omnigrass 4190.4231.9268.683.095.5250.4289.779.0
Omnigrass 5178.4197.1227.481.181.7205.5237.175.6
Sofsport91.3232.5269.982.593.6228.3265.778.1
Sprinturf112.0275.2323.382.3113.6261.1306.874.1
Wear5
Astroplay84.4213.9246.275.284.2204.9235.970.2
Astroturf128.5296.4359.086.8126.0282.9342.278.1
Experimental94.9217.9254.879.896.0230.9268.676.5
Fieldturf106.9259.9303.081.3106.6247.3288.881.0
Geoturf107.7269.4314.577.9110.2267.6312.983.9
Nexturf72.0172.6201.477.769.0154.1180.671.1
Omnigrass 41101.3275.5319.283.3102.0273.9316.878.0
Omnigrass 5188.2236.7272.980.389.2234.0269.975.7
Sofsport95.8244.1283.979.896.7240.1279.076.0
Sprinturf126.3316.2373.383.7126.2289.8341.475.1
LSD (p=0.05)10.238.845.6-9.735.542.3-

1Surface hardness was measured according to ASTM standard F355.
2HIC = Head Injury Index
3SI = Severity Index
4Subsurface temperature was measured 0.5 inch below the pile backing.
5F355 testing performed after wear simulating 96 games. September testing performed after wear simulating 88 games.

The question remains: how hard is too hard? Grooming of plots occurred on 4 and 5 Aug 2004.

The need for a systematic means of evaluating the impact attenuation of an installed North American football playing system has been amply demonstrated by the current difficulty in establishing the shock absorbing properties of new and aging systems. The aim of this specification is to provide a uniform means and relatively transportable method of establishing this characteristic in the field based on historical data. According to historical data, the value of 200 G is considered to be a maximum threshold to provide an acceptable level of protection to users.
The test method used in this specification (Procedure A of Test Method F 355), has been documented, through "unofficial" use for testing impact in fields for over 20 years. The development of this 2 ft fall height method can be traced back to the Ford and General Motors crash dummy tests of the 1960's, medical research papers from the 1960's and 1970's, and a Northwestern University study in which an accelerometer was fixed to the helmet of a middle linebacker to measure the impact received during actual play. This study found the impact to be 40 ft/lb that translates to the 20 lb at a height of 2 ft used in Procedure A of Test Method F 355. The maximum impact level of 200 average Gmax, as accepted by the U.S. Consumer Product Safety Commission, was adopted for use here.

All of the surfaces measured were well below the maximum level of 200 Gmax even after the equivalent of 296 games of simulated traffic over two years. While open to debate, I suggest the upper limit should be set to 175 Gmax using the F355 method A. After two years of simulated wear, all synthetic surfaces in this study measured well below the suggested upper limit for surface hardness.

Clegg Impact Soil Tester (CIST)

The CIST is the standard method to measure the surface hardness of natural turfgrass playing surfaces (American Society for Testing and Materials, 2000b). The device is similar to the F355 method. Both systems have a weighted missile that is dropped through a guide tube and impacts the playing surface. Each missile contains an accelerometer that measures how quickly the missile stops upon impact. This impact attenuation is representative of surface hardness. The two devices use different weights. The F355 method uses a 20 lb weight and the CIST uses a 5 lb weight but has a smaller impact surface area. The impact energy of both devices is very similar; however, the CIST results in a lower Gmax reading compared to the F355. The F355 method also has a velocimeter that measures the velocity of the missile just prior to impact. This gives the F355 method an added measure of accuracy since the velocity of the missile is actually measured during each drop. When using the CIST, the velocity of the missile is assumed. The velocity of the CIST missile has been measured, but for any individual drop, the user must assume that the missile is traveling at the calculated velocity and nothing has interfered with that velocity.

In a previous study, McNitt and Landschoot (2004) reported that under the conditions of their study the relationship between the Gmax values generated by the first drop of the F355 method can be compared to the values generated by the CIST using the regression equation (F355 x 0.66) - 9.3 = CIST. The regression coefficient for this equation was 0.95. Although this study was limited to the Sofsport infill system, the high regression coefficient would indicate that the CIST would be a suitable device to measure the surface hardness of Sofsport installations. After two years of data on varying infill systems at varying levels of wear we have generated the following regression equations:

For the first drop of both devices:

(F355 x 0.76) - 27.5 = CIST with an R squared value of 0.87.

For the first drop of the CIST and the average of the second and third drop in the same location using the F355:

(F355 x 0.81) - 27.1 = CIST with an R squared value of 0.81.

Using the above regression equation a Gmax of 200 measured with the F355 would be equivalent to a Gmax of 135 measured with the CIST and a 2.25 kg missile. None of the treatments in this study exceeded the 200 Gmax limit measured with the F355 or the 135 Gmax measured with the CIST (Table 2).

Table 2. Number of colonies per swab detected on R2A media from various sources in public spaces and an athletic training facility.
TreatmentGmax2
4 Aug27 Aug20 Nov
No Wear
Astroplay51.652.137.2
Astroturf97.099.370.9
Experimental61.664.841.5
Fieldturf66.765.548.1
Geoturf82.084.059.6
Nexturf48.651.251.4
Omnigrass 4161.362.642.9
Omnigrass 5145.148.429.7
Sofsport68.869.654.1
Sprinturf86.390.260.4
Wear3
Astroplay53.958.144.0
Astroturf113.5118.678.5
Experimental65.370.847.9
Fieldturf68.578.457.4
Geoturf79.783.765.3
Nexturf52.953.752.3
Omnigrass 4165.870.650.4
Omnigrass 5150.353.438.8
Sofsport74.278.556.4
Sprinturf93.7101.265.2
LSD (p=0.05)10.110.23.5

1Grooming of wear and no wear plots occurred on 9-10 Oct 2003.
2Surface hardness was measured using a Clegg Impact Tester equipped with a 2.25 kg hammer.
34 Aug testing performed after wear simulating 44 games. 27 Aug testing performed after wear simulating 84 games. 20 Nov testing performed after wear simulating 92 games and immediately after grooming.

We connected the CIST to a laptop computer and generated both the HIC and SI. The HIC and SI generated with the CIST were highly correlated to the Gmax value suggesting that Gmax is a sufficient measure of surface hardness (Table 3, 4 and 5).

Table 3. Surfaces that tested positive (+) for S. aureus colonies per swab detected.
TreatmentSeverity Index2Head Injury Criterion2
4 Aug27 Aug4 Aug27 Aug
No Wear
Astroplay93.797.680.282.1
Astroturf254.6261.6217.9224.0
Experimental130.6137.5112.5118.4
Fieldturf147.9140.8128.3121.9
Geoturf196.4204.0169.1175.8
Nexturf102.3105.186.591.5
Omnigrass 41131.9135.1113.5116.3
Omnigrass 5178.986.866.374.1
Sofsport159.2161.9137.5140.2
Sprinturf207.3220.3177.7189.4
Wear3
Astroplay104.6122.390.3105.8
Astroturf314.1327.1265.8275.4
Experimental140.9162.6121.0139.8
Fieldturf152.6190.0132.3164.6
Geoturf189.9207.5163.5178.8
Nexturf111.1114.296.5100.3
Omnigrass 41150.9166.9130.2143.8
Omnigrass 51101.7111.388.396.6
Sofsport180.9195.4156.2168.4
Sprinturf231.4256.2197.4218.3
LSD (p=0.05)21.337.418.431.4
Table 4. Severity Index (SI) of infill systems on 2004 determined with the Clegg Impact Tester prior to and after grooming¹.
TreatmentSeverity Index (SI)2
25 May20 Jul6 Aug3 Sep7 Sep13 Sep16 Sep29 Sep5 Oct14 Oct21 Oct28 Oct
No Wear
Astroplay39.047.752.257.962.372.958.255.357.954.255.358.8
Astroturf137.6135.3139.8156.4138.0146.5141.7138.4148.2144.4148.0145.5
Experimental58.659.174.183.091.577.777.164.379.276.868.775.4
Fieldturf71.971.984.590.0105.894.691.181.697.076.989.2101.5
Geoturf94.195.2106.3103.7108.9108.6105.8109.0106.5111.0110.8113.3
Nexturf45.754.253.056.853.558.261.258.058.563.672.258.7
Omnigrass 4162.062.064.679.385.182.570.666.375.571.565.372.3
Omnigrass 5131.440.241.949.756.258.946.440.850.042.840.342.2
Sofsport84.381.090.6105.0108.3109.393.194.198.690.295.296.3
Sprinturf80.991.611.5125.3124.0112.8112.8100.5116.7111.5108.4116.2
Wear3
Astroplay62.365.678.774.475.978.175.570.676.374.275.180.6
Astroturf157.2148.6161.0175.1150.9164.2150.0147.6161.2146.9157.3156.3
Experimental80.775.984.188.598.178.489.272.990.289.686.295.5
Fieldturf94.295.1101.2100.0104.0100.0103.3103.1108.1112.6107.8114.9
Geoturf111.4109.9113.9112.9118.0110.1117.6120.6120.8121.4122.8118.2
Nexturf55.858.661.794.164.164.863.467.870.772.679.869.9
Omnigrass 4183.377.482.6100.496.597.983.180.290.086.788.590.6
Omnigrass 5155.357.159.168.472.471.162.960.866.566.366.668.3
Sofsport98.192.199.4109.2112.6115.3101.495.4105.6100.4102.9106.5
Sprinturf120.2102.8124.3142.8140.2122.7126.9106.6125.5123.6117.8135.4
LSD (p=0.05)13.813.318.319.416.812.813.316.513.813.317.015.7

1Grooming of wear and no wear plots occurred on 4-5 Aug 2004.
2Surface hardness was measured using a Clegg Impact Tester equipped with a 2.25 kg hammer.
325 May testing performed after wear simulating 32 games. 20 Jul testing performed after wear simulating 96 games. 6 Aug testing performed after grooming. 7 Sep testing performed after wear simulating 8 games after grooming. 16 Sep testing performed after wear simulating 20 games after grooming. 29 Sep testing performed after wear simulating 36 games after grooming. 5 Oct testing performed after wear simulating 48 games after grooming. 14 Oct testing performed after wear simulating 64 games after grooming. 21 Oct testing performed after wear simulating 80 games after grooming. 28 Oct testing performed after wear simulating 92 games after grooming.

Table 5. Head Injury Criterion (HIC) of infill systems determined in 2004 with the Clegg Impact Tester prior to and after grooming¹.
TreatmentHead Injury Criterion (HIC)2
25 May20 Jul6 Aug3 Sep7 Sep13 Sep16 Sep29 Sep5 Oct14 Oct21 Oct28 Oct
No Wear
Astroplay33.540.645.050.052.458.648.947.146.847.148.151.2
Astroturf116.7116.0118.5131.1116.6124.4121.5118.6121.8124.7130.0125.1
Experimental50.951.263.471.077.565.766.061.964.566.759.665.0
Fieldturf62.862.773.678.491.680.478.670.981.586.977.888.5
Geoturf80.981.689.987.292.087.388.091.788.892.395.097.4
Nexturf40.045.242.445.644.247.747.949.849.756.663.551.7
Omnigrass 4153.953.854.667.373.168.157.655.963.761.356.662.6
Omnigrass 5126.831.834.140.347.946.535.533.541.335.035.236.9
Sofsport72.270.378.590.491.892.378.780.183.777.782.683.5
Sprinturf69.988.195.7106.8104.394.593.184.496.595.992.999.8
Wear3
Astroplay54.257.168.663.364.364.564.558.862.064.565.370.1
Astroturf132.5126.5135.9146.9126.6135.1127.8125.9132.4125.2137.6133.5
Experimental69.946.572.375.982.566.575.661.974.477.674.782.7
Fieldturf81.782.787.986.690.084.188.087.990.096.893.499.5
Geoturf95.894.397.995.2101.390.698.9101.3100.3101.6104.7101.2
Nexturf48.751.853.255.353.854.254.157.459.564.671.061.1
Omnigrass 4172.267.271.285.283.483.469.267.074.372.775.578.5
Omnigrass 5148.449.851.658.461.659.951.233.555.756.157.459.6
Sofsport84.879.685.694.294.795.484.780.187.284.788.492.0
Sprinturf102.988.1106.7120.7117.0103.3108.089.3103.4105.8101.0115.4
LSD (p=0.05)11.816.815.416.813.910.711.614.212.210.814.313.3

1Grooming of wear and no wear plots occurred on 4-5 Aug 2004.
2Surface hardness was measured using a Clegg Impact Tester equipped with a 2.25 kg hammer.
325 May testing performed after wear simulating 32 games. 20 Jul testing performed after wear simulating 96 games. 6 Aug testing performed after grooming. 7 Sep testing performed after wear simulating 8 games after grooming. 16 Sep testing performed after wear simulating 20 games after grooming. 29 Sep testing performed after wear simulating 36 games after grooming. 5 Oct testing performed after wear simulating 48 games after grooming. 14 Oct testing performed after wear simulating 64 games after grooming. 21 Oct testing performed after wear simulating 80 games after grooming. 28 Oct testing performed after wear simulating 92 games after grooming.

The lower half of the first two columns of data in Tables 2 and 3 is after simulated traffic equaling 44 and 84 games, respectively. The top half of the table is data collected from the half of the plot not receiving traffic. The third column (20 Nov) is data collected immediately after grooming. It is apparent from this data that grooming significantly reduced the surface hardness of all treatments in 2003. This was not the case in 2004 as grooming seemed to have little consistent affect on surface hardness (Table 6). This may be due to the aging of the systems or due to the unseasonably cold wet summer we experienced in 2004. Weekly Gmax measurements were collected using the CIST. The results are shown in Table 6. This was done in an attempt to monitor the duration of the effect of grooming on Gmax values. Our results indicate that the Gmax values of these surfaces remained relatively consistent from fall of 2003 through October 2004. It is unlikely that the effects of grooming last this long. In fact, the F355 data indicates that the surfaces trended higher in Gmax values in 2004 compared to 2003.

Table 6. Surface hardness (Gmax) of infill systems determined in 2004 with the Clegg Impact Tester prior to and after grooming¹ but were not consistent.
TreatmentGmax2
25 May20 Jul6 Aug3 Sep7 Sep13 Sep16 Sep29 Sep5 Oct14 Oct21 Oct28 Oct
No Wear
Astroplay33.836.538.340.041.544.240.139.243.939.339.841.2
Astroturf73.672.874.279.674.277.375.073.076.474.879.375.9
Experimental41.242.347.649.352.847.947.748.055.248.846.648.1
Fieldturf47.748.052.653.860.155.754.651.965.258.355.159.4
Geoturf58.258.362.060.963.360.761.462.561.862.863.464.6
Nexturf35.336.935.636.936.738.038.439.242.442.946.440.4
Omnigrass 4142.542.442.847.750.148.444.444.147.046.644.347.1
Omnigrass 5129.931.332.134.638.537.434.132.336.632.733.433.6
Sofsport51.250.353.658.258.859.753.754.556.953.755.856.5
Sprinturf52.058.165.467.666.262.764.561.565.765.765.066.6
Wear3
Astroplay42.443.848.245.446.046.746.344.454.946.647.148.8
Astroturf82.478.682.487.774.282.578.676.982.075.479.380.5
Experimental49.849.251.752.054.947.952.248.058.853.853.355.6
Fieldturf56.457.158.957.959.857.259.359.964.163.462.264.4
Geoturf64.263.764.564.366.462.066.066.866.267.068.666.7
Nexturf38.539.239.640.240.040.240.241.555.745.248.143.9
Omnigrass 4150.548.850.555.155.155.149.649.251.551.644.353.8
Omnigrass 5138.539.139.842.643.943.539.538.641.842.233.443.7
Sofsport56.754.656.760.360.761.756.855.259.157.258.759.9
Sprinturf68.364.471.374.172.167.871.665.569.871.269.874.3
LSD (p=0.05)5.55.86.97.06.45.15.87.28.65.96.76.2

1Grooming of wear and no wear plots occurred on 4-5 Aug 2004.
2Surface hardness was measured using a Clegg Impact Tester equipped with a 2.25 kg hammer.
325 May testing performed after wear simulating 32 games. 20 Jul testing performed after wear simulating 96 games. 6 Aug testing performed after grooming. 7 Sep testing performed after wear simulating 8 games after grooming. 16 Sep testing performed after wear simulating 20 games after grooming. 29 Sep testing performed after wear simulating 36 games after grooming. 5 Oct testing performed after wear simulating 48 games after grooming. 14 Oct testing performed after wear simulating 64 games after grooming. 21 Oct testing performed after wear simulating 80 games after grooming. 28 Oct testing performed after wear simulating 92 games after grooming.

These data may be a result of the cool wet conditions that prevailed in 2004. Another possibility is that as these systems age and become less resilient, the heavier missile of the F355 method, which takes the average of the second and third successive drop in the same location, is experiencing a higher Gmax due to the heavier load at impact. After maximum impact attenuation of the infill and fiber system is reached, the accelerometer in these devices will begin to be affected by the impact attenuation of the surface below the backing. Henderson (1986) found that a rock can be sensed by the F355 method when it is four inches below the surface of a natural turfgrass playing field. The reason for this difference will likely become clearer as successive years of data are collected. Currently, we are suggesting the CIST as a tool for grounds managers to monitor their field throughout the season and recommending the F355 device be employed at least annually.

The following data is provided to give some reference points for the Gmax values generated using the CIST.

Table 7. Impact values for high school fields vs. impact values for other surfaces
SurfaceHammer
2.25 kg
Gmax
High school fields33-167
Frozen practice field303
Tiled, concrete basement floor1,280
Carpet and pad on tiled concrete floor190
Carpet and pad on hardwood floor134

Gmax = maximum deceleration

During 2004, we applied simulated foot traffic to a very well established Kentucky bluegrass (Poa pratensis, L.) turfgrass (33% Liberator, 33% Washington and 33% Touchdown) at the same rate and intensity as we applied it to the synthetic turf systems.

A significant amount of turfgrass cover was lost. On the 9 Jul 205 rating date, the average turf cover was 65% (Fig. 16). In order to coincide with grooming of the synthetic turf, the natural turf area was aerated in August using 3/4 inch tines on 3 x 2 in. center and rested for about one month. The plots recovered to about 90% turf cover (Fig. 17). Wear continued and by 8 Nov 2004 the plot area averaged 40 - 45% turf cover (Fig. 18). This turf area was well maintained. During the 2004 growing season nitrogen fertilization on this plot area was 3.5 lbs N per thousand feet squared and irrigation was applied to prevent drought stress. The soil was a Hagerstown silt loam. Prior to the beginning of simulated wear, the thatch thickness of the plot area averaged 3/4 in. The data listed in Table 8 indicate that the surface hardness of the natural turf area was the same or higher than most of the infill systems' Gmax values listed in Table 2. On a native soil turfgrass surface, Gmax is greatly affected by soil moisture. Soil moisture values for some rating dates are listed and were high for 2004 as it was a very wet summer and fall. During dry conditions, we would expect these values to increase.

Table 8. Surface hardness (Gmax) and soil moisture content in 2004 of a natural turfgrass test area

Gmax
Clegg1F3333
25 May20 Jul7 Sep13 Sep16 Sep29 Sep5 Oct14 Oct21 Oct28 Oct2 Jul
Wear250.470.174.868.484.170.383.679.356.361.088.3
No Wear50.455.566.966.267.459.367.969.753.754.983.3

1Surface hardness was measured using a Clegg Impact Tester equipped with a 2.25 kg hammer.25 May testing performed after wear simulating 32 games. 20 Jul testing performed after wear simulating 96 games. Aerification of wear and no wear areas occurred on 6 Aug 2004. The area was aerified with 0.75" hollow tines. 7 Sep testing performed after wear simulating 8 games after aerification. 13 Sep testing performed after wear simulating 12 games after aerification. 16 Sep testing performed after wear simulating 20 games after aerification. 29 Sep testing performed after wear simulating 36 games after aerification. 5 Oct testing performed after wear simulating 48 games after aerification. 14 Oct testing performed after wear simulating 64 games after aerification. 21 Oct testing performed after wear simulating 80 games after aerification. 28 Oct testing performed after wear simulating 92 games after aerification.
2Plots receiving wear treatments were exposed to wear as eight passes three times per week with the Brinkman Traffic simulator beginning on 21 Apr and ending on 8 Nov.
3Surface hardness was measured according to ASTM standard F355. 2 Jul testing performed after wear simulating 96 games.

% Moisure4
2 Jul20 Jul16 Sep29 Sep28 Oct
Wear29.936.023.835.136.1
No Wear30.734.930.233.734.2

4Percent soil moisture (M3M-3) was determined using a Dynamax Theta Meter Type HH1 at the same time gmax reading were collected.

Infill Media and Underlying Pad

The following is a short description of a prior study conducted by McNitt and Landschoot (2004). For a copy of the complete study click the reference below.

The objective of this study was to evaluate the surface hardness of varying configurations of an infilled synthetic turf system called SofSportTM under wet and dry conditions. Specifically, we wanted to 1) determine the effect of underlying pad thickness and type, infill media depth, sand sizes, and sand to crumb rubber ratio, on surface hardness as measured by the F355 method and the CIST and 2) compare the F355 method with the CIST to determine if one method is preferred when testing synthetic infill systems. Surface hardness differences between pad thickness and types were small but all pad treatments had lower surface hardness values compared to the no-pad treatments. Infill media depth did not affect surface hardness under dry conditions. Under wet conditions, the 38 mm infill media depth resulted in lower surface hardness than the 25 mm depth. The mixing of sand and crumb rubber infill media resulted in lower surface hardness values than sand or crumb rubber alone. When mixed with crumb rubber, finer sands measured higher in surface hardness than coarser sands. Under the conditions of this study the relationship between the Gmax values generated by the F355 method can be compared to the values generated by the Clegg Impact Soil Tester using the regression equation F355 x 0.66 - 9.3 = Clegg Impact Soil Tester. The regression coefficient for this equation was 0.95 and indicates that the Clegg Impact Soil Tester would be a suitable device to measure the surface hardness of SofSport installations.

  • McNitt, A.S., P.J. Landschoot, and D. Petrunak. 2004. Evaluation of playing surface quality of an infilled synthetic turf system. Acta Horticulture 661:559-565.

Traction Data Collection

For all results in this section it should be noted that this preliminary data is from the first two years of a long term study. These results will be updated as more data is collected.

Translational, rotational, static, and dynamic traction have been defined by Shorten and Himmelsbach (2002).

Translational traction refers to the traction that resists the shoe's sliding across the surface. For the athlete, high translational traction equates to the shoe gripping the surface and low translational traction means the shoe tends to slip.

Rotational traction refers to the traction that resists rotation of the shoe during pivoting movements. For the athlete, high rotational traction equates to a greater tendency for foot fixation during changes of direction and low rotational traction means the shoe tends to release from the surface more easily.

Static and dynamic traction represent slightly different aspects of the shoe-surface interaction. Static traction is the resistance to sliding or pivoting when there is no movement between the shoe and the surface. Static traction forces tend to resist the initiation of sliding or pivoting. Dynamic traction is the resistance that occurs during a sliding or pivoting motion. Dynamic traction forces tend to resist or decelerate pivoting motions.

In this study traction was measured using Pennfoot (McNitt et al., 1997). Pennfoot conforms to the proposed traction standard ASTM WK486 (American Society for Testing and Materials, 2000c) standard traction measurements and is shown in Fig. 19.

Description and Operation of Pennfoot

Pennfoot consists of a frame which supports a steel leg with a cast aluminum foot pinned on the lower end of the leg. We cast the simulated foot from a size 10 foot mold and the foot can be fitted with different athletic footwear (Fig. 20). Two holes located on top of the foot are used for connection with the leg. The first hole located toward the toe allows us to raise the heel off the ground and distribute the weight on the ball of the foot. We took all traction measurements in this study with the forefoot in contact with the surface and the heel of the foot raised off the ground.

Pennfoot allows us to measure rotational or translational traction. For translational traction the linear force is created by a single pulling piston that is connected to the heel of the foot (Fig. 21). The pressure applied to the piston is created with a motorized hydraulic pump and monitored with a pressure transducer connected to a computer. The pressure readings are converted to Newtons (N) by multiplying the effective area of the pulling piston by the amount of pressure required to maintain movement of the shoe. The rate of linear travel is approximately 0.5 m s -1 . Linear traction is thus measured as the amount of horizontal force (N) required to maintain translational movement at the given rate. It is customary to report a traction coefficient as the horizontal force divided by the vertical force. In the primary experiment all traction measurements were taken using a vertical force, or loading weight of 237 lbs. and a Nike Air Zoom high top shoe (Fig 22. original shoe). During 2004, we also tested a standard 7 post shoe (Fig 23. 7 shoe). In 2004, we tested select surfaces in both wet and dry conditions and we measured traction on all surfaces at a lower loading weight (119 lbs.).

When using Pennfoot to measure rotational traction, the rotating horizontal force is created by two pistons which are horizontally mounted on angle iron 38.1 cm above the ground as measured with the machine in position to take a measurement (Fig. 24). We connected a strike plate to the simulated leg for the pistons to push against. A lower collar around the simulated leg prevented it from tilting while the rotational force was applied. For a thorough description of design rationale and construction details of Pennfoot see McNitt et al. (1997).

The experimental design for the primary experiment was a completely random split-plot statistical design with three replications. The split was wear and no wear. Three Pennfoot measurements were taken for each subplot in this study. The means of the three linear and three rotational traction measurements were analyzed using analysis of variance and Fisher's least significant difference test at the 0.05 level. A LSD was not calculated when the F ratio was not significant at the 0.05 level.

Results and Discussion

The following is quoted directly from a study conducted by Shorten and Himmelsbach (2002).

Because of the link between foot fixation and knee injuries, resistance to rotation (rotational traction) between the shoe and the ground should be as low as possible providing adequate translational traction is maintained.

Other studies have postulated a link between higher resistance to rotation and injury rates. While many reports have shown that injury rates are 30 to 50% higher on (traditional) artificial turf (Cameron and Davis, 1973; Henschen et al., 1989; Skovron et al., 1990; Powell and Shootman, 1992; Zemper, 1989) others have failed to find significant differences in injury rates (Clarke and Miller, 1977; Culpepper and Morrison, 1987) One concern with all of these studies is that only surface effects were considered while it is the combination of both the shoe and the surface that is implicated in traction related injuries.

Torg et al. (1978) found that high school football players wearing shoes with shorter cleats had a lower injury rate than those using longer cleats, a difference attributable to differences in the shoes' rotational traction.

More recently, Lambson et al. (1999) studied the relationship between the rotational resistance of shoes and the incidence of anterior cruciate ligament tears among 3119 high school football players. Shoes with peripheral cleats were associated with a significantly higher injury rate, compared with other shoe types.

In summary, there is strong evidence that excessive resistance to rotation at the shoe-surface interface increases the risk of foot fixation and hence of lower extremity injuries. There is also ample evidence that this mechanism contributes to a higher rate of injury among football players playing on (traditional) artificial turf, although this issue remains controversial among parties with interests in artificial turf systems.

For these reasons, we chose to measure both rotational and translational (linear) traction.

Translational and rotational traction values for treatments are shown in Tables 9 and 10.

Table 9. Linear traction determined in 2003 by ASTM traction standard and 237 pounds of vertical force prior to and after grooming 1.
TreatmentSeptember 2003October 2003
Static2Dynamic3StaticDynamic
No Wear
Astroplay1.221.101.421.17
Astroturf1.651.461.831.41
Experimental1.321.051.501.14
Fieldturf1.421.211.501.19
Geoturf1.371.241.481.29
Nexturf1.311.001.511.15
Omnigrass 411.301.121.381.13
Omnigrass 511.371.201.461.18
Sofsport1.301.161.561.26
Sprinturf1.231.071.441.13
Wear4
Astroplay1.301.041.471.18
Astroturf1.521.461.601.33
Experimental1.411.171.431.15
Fieldturf1.351.041.581.22
Geoturf1.261.121.441.31
Nexturf1.381.061.501.21
Omnigrass 411.451.231.551.27
Omnigrass 511.401.251.561.32
Sofsport1.361.211.441.24
Sprinturf1.251.151.381.13
LSD (p=0.05)0.140.130.110.16

1Grooming of wear and no wear plots occurred on 9-10 2003.
2Static traction.
3Dynamic traction.
4September testing performed after wear simulating 88 games. October testing performed after wear simulating 92 games.

Table 10. Rotational traction determined in 2003 by ASTM traction standard prior to and after grooming 1.
TreatmentRotational traction (Nm)2
24-Sep30-Oct
No Wear
Astroplay66.766.8
Astroturf70.969.0
Experimental63.067.7
Fieldturf66.063.0
Geoturf69.368.1
Nexturf67.767.0
Omnigrass 4166.065.9
Omnigrass 5168.067.3
Sofsport64.767.9
Sprinturf64.665.5
Wear3
Astroplay68.967.1
Astroturf69.168.8
Experimental67.965.4
Fieldturf68.066.5
Geoturf69.670.4
Nexturf70.367.1
Omnigrass 4166.765.4
Omnigrass 5167.667.2
Sofsport68.767.9
Sprinturf66.266.6
LSD (p=0.05)6.62.9

1Grooming of wear and no wear plots occurred on 9-10 Oct 2003.
2Rotational traction.
324 Sep testing performed after wear simulating 76 games. 30 Oct testing performed after wear simulating 92 games.

During 2003, there were few meaningful traction differences between synthetic turf systems. Traditional Astroturf measured consistently higher in linear traction compared to the infill systems. This trend was not evident in the rotational traction results in 2003.

The 30 Oct 2003 data were collected shortly after grooming had taken place. Translational traction tended to increase after grooming whereas rotational traction tended to have no change or trend slightly lower. This data indicates that, immediately after grooming, an athlete will experience increased translational (linear) traction and either no change or a slight decrease in rotational traction, thus allowing football lineman more traction when pushing but affecting no change or a slight reduction in the rotational foot fixation that Shorten and Himmelsbach (2002) state has a direct affect on lower extremity injuries.

In 2004, there continued to be a trend of increased linear traction after grooming for the no wear treatments but the trend was less evident in the treatments receiving wear (Tables 11 and 12). It may be that as these systems age, grooming will have a diminished affect on linear traction.

Table 11. Linear and rotational traction determined in 2004 by ASTM traction standard and 237 pounds of vertical force prior to grooming¹.
TreatmentStatic2Dynamic3Rotational4
DryWet5DryWetDryWet
No Wear
Astroplay1.43-1.24-90.6-
Astroturf1.59-1.33-88.9-
Experimental1.49-1.18-98.0-
Fieldturf1.531.301.221.00109.484.6
Geoturf1.51-1.36-87.5-
Nexturf1.47-1.20-89.6-
Omnigrass 411.471.211.251.0390.579.3
Omnigrass 511.491.231.271.0184.790.0
Sofsport1.53-1.26-81.0-
Sprinturf1.431.101.140.9891.978.1
LSD0.110.040.080.0216.20.1
Wear6
Astroplay1.52-1.25-92.6-
Astroturf1.54-1.39-81.3-
Experimental1.51-1.27-82.7-
Fieldturf1.641.291.301.0584.183.6
Geoturf1.45-1.34-72.1-
Nexturf1.50-1.23-84.1-
Omnigrass 411.641.291.301.0589.280.8
Omnigrass 511.581.281.341.0879.081.8
Sofsport1.48-1.22-86.3-
Sprinturf1.481.181.210.9987.877.4
LSD0.110.040.080.0216.20.1

1Testing was performed on 20-21 Jul, 23 Jul, and 28 Jul after wear simulating 96 games. The shoe used for testing was a Nike Air Zoom high-top shoe with a molded sole.
2Static traction
3Dynamic traction
4Rotational traction
5Readings were taken when the surface was wet following 0.28" rain or 0.25" irrigation.
6Plots receiving wear were exposed to wear as eight passes three times per week with the Brinkman Traffic simulator beginning on 21 Apr and ending on 8 Nov 2004. Plots were groomed on 4-5 Aug 2004.

Table 12. Linear and rotational traction determined in 2004 by ASTM traction standard and 237 pounds of vertical force after grooming¹.
TreatmentStatic2Dynamic3Rotational4
No Wear
Astroplay1.471.2888.6
Astroturf1.701.5884.6
Experimental1.521.2281.7
Fieldturf1.571.2876.3
Geoturf1.521.3780.2
Nexturf1.511.3078.1
Omnigrass 411.501.2879.1
Omnigrass 511.531.3174.1
Sofsport1.551.2782.3
Sprinturf1.421.1581.7
LSD0.070.107.5
Wear5
Astroplay1.531.3276.4
Astroturf1.581.3491.8
Experimental1.531.3478.1
Fieldturf1.511.3081.7
Geoturf1.451.3179.6
Nexturf1.511.2974.8
Omnigrass 411.591.3184.9
Omnigrass 511.581.3878.6
Sofsport1.491.3382.1
Sprinturf1.501.2879.6
LSD0.070.107.5

1Testing was performed from 31 Aug to 2 Sep after wear simulating 96 games and grooming of the plots. Grooming occurred on 4-5 Aug 2004. The shoe used for testing was a Nike Air Zoom high-top shoe with a molded sole.
2Static traction
3Dynamic traction
4Rotational traction
5Plots receiving wear were exposed to wear as eight passes three times per week with the Brinkman Traffic simulator beginning on 21 Apr and ending on 8 Nov 2004. Plots were groomed on 4-5 Aug 2004.

During 2004, grooming resulted in a greater reduction in rotational traction compared to 2003 (Tables 11 and 12). This was true regardless of shoe type. The data in Tables 13 and 14 indicate that grooming resulted in a consistent increase in linear traction, measured using a nine post shoe, and a general but less consistent decrease in rotational traction.

Table 13. Linear and rotational traction determined in 2004 by ASTM traction standard and 237 pounds of vertical force prior to grooming¹ using a 7 post cleated shoe.
TreatmentStatic2Dynamic3Rotational4
No Wear
Astroplay1.411.1379.4
Astroturf1.251.1879.6
Experimental1.441.1782.9
Fieldturf1.521.3670.4
Geoturf1.421.1277.6
Nexturf1.170.8679.7
Omnigrass 411.371.1270.9
Omnigrass 511.301.0780.3
Sofsport1.571.2884.1
Sprinturf1.421.1580.6
LSD0.100.0610.8
Wear5
Astroplay1.471.1478.6
Astroturf1.201.09101.2
Experimental1.401.1180.1
Fieldturf1.641.3377.9
Geoturf1.411.0982.5
Nexturf1.080.8480.6
Omnigrass 411.471.1577.8
Omnigrass 511.481.1675.8
Sofsport1.541.1784.0
Sprinturf1.481.1282.8
LSD0.100.0610.8

1Testing was performed from 22 Jul and 3 Aug after wear simulating 96 games. The shoe used for testing was a Reebok MidVisious 7 POST shoe with screw-in cleats.
2Static traction
3Dynamic traction
4Rotational traction
5Plots receiving wear were exposed to wear as eight passes three times per week with the Brinkman Traffic simulator beginning on 21 Apr and ending on 8 Nov 2004. Plots were groomed on 4-5 Aug 2004.

Table 14. Linear and rotational traction of plots received wear determined in 2004 by ASTM traction standard and 237 pounds of vertical force after grooming¹ using a 7 post cleated shoe.
TreatmentStatic2Dynamic3Rotational4
Astroplay1.621.2372.8
Astroturf1.231.1293.6
Experimental1.591.2174.2
Fieldturf1.721.4186.7
Geoturf1.741.2184.6
Nexturf1.220.9178.5
Omnigrass 411.671.2875.6
Omnigrass 511.581.2688.0
Sofsport1.661.2177.5
Sprinturf1.611.2181.8
LSD0.100.1810.3

1Testing was performed on 27 Aug and 2 Sep 2004 after wear simulating 96 games and grooming of the plots. The shoe used for testing was a Reebok MidVisious 7-post shoe with screw-in cleats.
2Static traction
3Dynamic traction
4Rotational traction

When traction was measured on the various surfaces during wet conditions traction was generally reduced (Table 11). A lower loading weight resulted in higher traction coefficients for linear measurements. It is not customary to calculate rotational traction coefficients; however, the data in Table 15 was collected using a loading weight that was half that of the data in Table 11. When considered proportionally, the traction values reported in Table 15 follow the same trend as the linear traction values.

Table 15. Linear and rotational traction determined in 2004 by ASTM traction standard and 119 pounds of vertical force prior to grooming¹.
TreatmentStatic2Dynamic3Rotational4
No Wear
Astroplay1.611.4479.0
Astroturf2.431.8889.0
Experimental1.731.3787.8
Fieldturf1.781.3780.3
Geoturf1.711.5176.6
Nexturf1.501.3887.0
Omnigrass 411.641.3684.6
Omnigrass 511.691.3676.4
Sofsport1.701.4582.5
Sprinturf1.501.3480.0
LSD0.150.089.7
Wear5
Astroplay1.781.5182.2
Astroturf2.351.8079.2
Experimental1.771.4586.3
Fieldturf1.881.4878.6
Geoturf1.731.5383.7
Nexturf1.631.4076.7
Omnigrass 411.841.4890.4
Omnigrass 511.841.4876.3
Sofsport1.821.5175.0
Sprinturf1.661.5082.9
LSD0.150.089.7

1Testing was performed from 21-22 Jul and 2 Aug after wear simulating 96 games. The shoe used for testing was a Nike Air Zoom high-top shoe with a molded shoe.
2Static traction
3Dynamic traction
4Rotational traction
5Readings were taken when the surface was wet following 0.28" rain or 0.25" irrigation.
6Plots receiving wear were exposed to wear as eidht passes three times per week with the Brinkman Traffic simulator beginning on 21 Apr and ending on 8 Nov 2004. Plots were groomed on 4-5 Aug 2004.

Comparing the data from 2004 to the data collected in 2003, linear traction decreased with age while rotational traction increased. With only two years of data it is impossible to predict if this trend will continue.

Traction measurements were collected on the natural turfgrass areas during 2004 and are shown in Table 16. Comparing traction values using the same loading weight and shoe type, the data indicates similar or lower linear traction and similar or higher rotational traction of the natural turfgrass compared to synthetic surfaces. Very little data was collected on the natural turfgrass as turf and soil conditions fluctuated. The natural turfgrass data is from one rating date and one soil moisture condition.

Table 16. Translational (static and dynamic) and rotational traction 1 of Kentucky bluegrass (Poa pratentis, L.) in 2004 using tow shoes and two loading weights.
7 Post shoe2 237lb leg apparatus3
StaticDynamicRotational (Nm)
Wear41.661.50102.3
No Wear1.681.6395.7
Molded sole shoe5 119lb leg apparatus6
StaticDynamicRotational (Nm)
Wear41.411.1772.1
No Wear1.511.14105.4
Molded Sole shoe 237lb leg apparatus7
StaticDynamicRotational (Nm)
Wear41.251.0197.3
No Wear1.190.93108.3

1Traction was measured using Pennfoot, which conforms to the proposed traction standard ASTM WK486
2The shoe used is a Reebok MidViscious 7 post shoe with screw-in cleats.
3Static and dynamic traction data were collected on 22 Jul 04. Rotational traction data were collected on 3 Aug 04.
4The area receiving wear was exposed to wear as eight passes three times per week with the Brinkman Traffic simulator beginning on 21 Apr 04 and ending on 8 Nov 04. Data were collected from the area receiving wear after traffic simulating 96 games.
5The molded sole shoe used is a Nike Air Zoom turf shoe.
6Static and dynamic traction data were collected on 22 Jul 04. Rotational traction data were collected on 2 Aug 04.
7Static and dynamic traction data were collected on 22 Jul 04. Rotational traction data were collected on 28 Jul 04.

Abrasion

Abrasiveness was measured using ASTM F1015 method (ASTM 2000e). Friable foam blocks were attached to a weighted platform that was pulled over the playing surface in four directions (Fig 25 and 26). The weight of foam abraded away determines the relative abrasiveness of the surface. The friable foam blocks used as the test material were rigid closed-cell isocyanurate. An abrasiveness index is calculated by taking the weight loss for each set of four blocks in grams and dividing by 0.0606 as per ASTM F1015.

Abrasion data is shown in Table 17. All infilled treatments were less abrasive than Astroturf. For treatments receiving wear, the abrasion index was lower in 2004 (Table 18) compared to 2003. This trend was not evident in the no-wear treatments. Grooming tended to lower the abrasiveness of the treatments. We continue to try to modify the abrasion testing method so we can produce data on natural turf.

Table 17. Abrasion index of ten synthetic turf products in 2003 prior to and after grooming.¹
TreatmentAbrasion Index2
7-Aug30-Sep31-Oct
No Wear
Astroplay29.034.932.8
Astroturf56.467.065.4
Experimental35.544.042.1
Fieldturf32.336.833.2
Geoturf47.257.055.2
Nexturf25.334.434.1
Omnigrass 4131.635.735.7
Omnigrass 5131.835.035.7
Sofsport32.238.537.6
Sprinturf31.437.036.9
Wear3
Astroplay35.444.340.0
Astroturf59.168.661.9
Experimental35.946.543.5
Fieldturf32.742.538.9
Geoturf46.056.853.4
Nexturf32.638.233.9
Omnigrass 4137.341.739.0
Omnigrass 5138.641.338.1
Sofsport36.238.137.5
Sprinturf34.641.641.5
LSD (p-0.05)3.53.641.5

1Grooming of wear and no wear plots occurred on 9-10 Oct 2003.
2Abrasion index is determined by pulling foam blocks in a weighted sled across the plots in 4 directions and determining the loss (by weight) of the blocks. Abrasiveness index =[(starting block weight - final block weight)/6]*100.
37 Aug testing performed after wear simulating 44 games. 30 Sep testing performed after wear simulating 88 games. 31 Oct testing performed after wear simulating 92 games.

Table 18. Abrasion index of ten synthetic turf products in 2004 prior to and after grooming¹
TreatmentAbrasion index2
9 Jul26 Aug
No Wear
Astroplay33.733.6
Astroturf51.553.9
Experimental41.138.1
Fieldturf32.432.5
Geoturf44.651.0
Nexturf30.529.3
Omnigrass 4137.735.1
Omnigrass 5135.634.3
Sofsport33.836.1
Sprinturf38.938.6
Wear3
Astroplay39.035.5
Astroturf50.848.8
Experimental38.835.1
Fieldturf36.235.4
Geoturf43.846.3
Nexturf34.329.5
Omnigrass 4137.732.4
Omnigrass 5141.135.9
Sofsport31.636.1
Sprinturf40.137.2
LSD (p=0.05)10.03.4

1Grooming of wear and no wear plots occurred on 4-5 Aug 2004.
2Abrasion index is determined by pulling foam blocks in a weighted sled across the plots in 4 directions and determining the loss (by weight) of the blocks. Abrasiveness index =[(starting block weight - final block weight)/6]*100.
39 Jul testing performed after wear simulating 96 games. 26 Aug testing performed after grooming of all plots on 4-5 Aug.

A Survey of Microbial Popluations in Infilled Synthetic Turf Fields

Staphylococcus aureus is a bacterium that is a common inhabitant of human skin and can cause various types of skin or soft tissue infections (Marples, et al, 1990). S. aureus has also been implicated in certain types of food poisoning (Bennet and Lancette, 1998) and in serious medical problems such as toxic shock syndrome. Strains of S. aureus that are resistant to common antibiotics are becoming more common, particularly in medical settings. There have been reports recently of methicillin-resistant S. aureus causing infection in athletes (Begier, et al, 2004). With the increase in athlete infections, there is growing concern regarding the role of infilled turf systems (Seppa, 2005). While there is some indication that the source of these bacteria may be more closely associated with locker room activity than with the infill system (Begier, et al, 2004; Kazakova, et al, 2005), conclusive evidence is not currently available.

The objective of this survey was to determine the microbial population of several infilled synthetic turf systems as well as natural turfgrass fields. In addition, other surfaces from public areas and from an athletic training facility were also sampled. Colonies suspected to be S. aureus were positively or negatively identified.

Materials & Methods

Sample Collection

All samples in this study were collected between June 15 and June 30, 2006. Infilled synthetic turf systems were located at facilities in Pennsylvania and were in use by all levels of play ranging from elementary to professional athletes. Infill material samples were collected from both a 'high use' and a 'low use' area of each field. A 'high use' area typically was a goal mouth or, for a football only field, an area between the 30- and 40-yard lines between the hash marks. A 'low use' area was typically an area toward the edge of the field (but within the field of play) or an end zone. Approximately 2-3 ml of infill material were removed from each area of the field using a sterile test tube inserted directly into the infill. Pile fiber samples were also collected from many fields by clipping several fibers from the backing and transferring the fibers to a sterile test tube. Samples were stored in a cooler and processed as soon after collection as possible.

Sample Processing

Approximately 0.075 g of infill material was transferred to a test tube containing 10 ml sterile 0.1% peptone broth. The sample was agitated for 30 seconds Serial dilutions of each sample were plated up to 10-3 on both R2A agar for total organism populations and Baird-Parker agar, a selective media for Staphylococcus (Bennet and Lancette, 1998). Duplicate platings were made for each media and each dilution. Petri plates were parafilmed and incubated at room temperature and colony counts were made 72 hours after processing. Samples on Baird-Parker agar were also observed again after 5 days. Calculations were then made to determine the number of colony forming units (CFU) per gram of infill material.

For comparison purposes, soil samples were also collected from a native soil and a sand based natural turfgrass athletic field. Samples were processed in the same manner as the infill material samples with 0.2 grams of soil being used for processing.

Sampling of Other Surfaces

Samples were collected from common surfaces in public areas as well as from various surfaces in an athletic training area. Samples were collected by swabbing surfaces with sterile cotton swabs. Random individuals were also tested by swabbing hands and/ or face. Both R2A and Baird-Parker agar plates were wiped with the sterile swabs. Plates were incubated at room temperature and colony counts were conducted after 72 hours for R2A agar and again at 5 days for Baird-Parker media.

Identification of Staphylococcus aureus colonies

Gram stains and latex agglutination tests (Essers and Radebold, 1980) were performed on colonies suspected of being S. aureus. Several potential S. aureus colonies isolated from hand and facial swabs were also included in the testing.

Results and Discussion

Field Samples

The results of total microbial populations are shown in Table 1. While microbes exist in the infill media the number was low compared to natural turfgrass field soils. It should be remembered that microbes tend to be present on most surfaces humans come in contact with and the simple presence of microbes should not be cause for concern. In fact, many products on the market claim to boost the microbial populations of natural turfgrass soils with higher microbial populations considered to be beneficial.

Table 1. Colony forming units (CFU) detected on R2A media per gram of crumb rubber.
Treatment28-31 Jul 20038-12 Sep 2003
Gmax1HIC2SI3Sub temp (°F)4Infill depth (cm)GmaxHICSISub temp (°F)Infill depth (cm)
No Wear
Astroplay75.0173.5201.178.94.279.7183.8231.373.04.0
Astroturf113.3244.7293.182.20.7102.1244.0285.978.2NA
Experimental81.1182.2211.776.53.683.1195.9227.975.43.5
Fieldturf93.1203.4237.283.54.394.4223.1259.674.84.3
Geoturf101.6240.2282.596.62.8101.1234.7273.770.03.3
Nexturf62.1130.5152.574.72.370.2158.2184.580.92.2
Omnigrass 4183.3198.2229.783.44.087.7208.6241.969.23.9
Omnigrass 5172.5170.2196.578.14.995.0234.9272.671.14.9
Sofsport88.8204.6238.788.43.2105.0258.1305.672.73.3
Sprinturf101.9235.3276.079.22.6102.8236.7278.773.62.8
Wear5
Astroplay75.7174.0202.279.34.282.1196.5227.572.04.0
Astroturf109.6227.1274.181.90.7108.3258.9305.079.0NA
Experimental86.9207.2240.376.03.581.1190.1221.275.43.2
Fieldturf95.3214.2250.379.24.295.1225.5261.975.84.2
Geoturf95.4217.9254.588.73.1100.6239.7279.371.33.1
Nexturf64.8139.4164.175.02.268.7152.0177.687.31.8
Omnigrass 4189.0221.5256.782.73.893.2228.9264.969.23.7
Omnigrass 5178.3193.0222.882.14.890.9219.9255.371.74.6
Sofsport88.9209.8244.286.83.1103.8252.8299.772.63.1
Sprinturf106.6253.6296.778.12.599.2232.0273.173.22.7
LSD (p=0.05)6.124.128.04.50.38.029.233.82.50.2

1Surface hardness was measured according to ASTM standard F355.
2HIC = Head Injury Index
3SI = Severity Index
4Subsurface temperature was measured 0.5 inch below the pile backing.
5July testing performed after wear simulating 36 games. September testing performed after wear simulating 88 games.

Pile fiber samples were also collected from several fields. CFUs for fiber samples range from 200-2933 CFUs per fiber sample (2 fibers approximately 1 cm long) indicating that the fibers alone generally exhibited lower microbial populations compared to the infill.

Microbial colonies isolated from field samples generally included both fungi and bacteria. Some fields had predominantly one organism type while other fields contained a variety of organisms. In order to positively identify the presence of S. aureus , three procedures were used. No colonies isolated from any crumb rubber or fiber samples tested positive for S. aureus via selective media, gram stain or latex agglutination tests.

Other Surfaces

Surfaces other than athletic playing surfaces were tested for the presence of microbes and S. aureus. These surfaces are not granulated and thus the results are listed in Table 2 as total colony number as opposed to CFU per gram of granulated material.

Table 2. Number of colonies per swab detected on R2A media from various sources in public spaces and an athletic training facility.
TreatmentGmax2
4 Aug27 Aug20 Nov
No Wear
Astroplay51.652.137.2
Astroturf97.099.370.9
Experimental61.664.841.5
Fieldturf66.765.548.1
Geoturf82.084.059.6
Nexturf48.651.251.4
Omnigrass 4161.362.642.9
Omnigrass 5145.148.429.7
Sofsport68.869.654.1
Sprinturf86.390.260.4
Wear3
Astroplay53.958.144.0
Astroturf113.5118.678.5
Experimental65.370.847.9
Fieldturf68.578.457.4
Geoturf79.783.765.3
Nexturf52.953.752.3
Omnigrass 4165.870.650.4
Omnigrass 5150.353.438.8
Sofsport74.278.556.4
Sprinturf93.7101.265.2
LSD (p=0.05)10.110.23.5

1Grooming of wear and no wear plots occurred on 9-10 Oct 2003.
2Surface hardness was measured using a Clegg Impact Tester equipped with a 2.25 kg hammer.
34 Aug testing performed after wear simulating 44 games. 27 Aug testing performed after wear simulating 84 games. 20 Nov testing performed after wear simulating 92 games and immediately after grooming.

Table 3. Surfaces that tested positive (+) for S. aureus colonies per swab detected.
TreatmentSeverity Index2Head Injury Criterion2
4 Aug27 Aug4 Aug27 Aug
No Wear
Astroplay93.797.680.282.1
Astroturf254.6261.6217.9224.0
Experimental130.6137.5112.5118.4
Fieldturf147.9140.8128.3121.9
Geoturf196.4204.0169.1175.8
Nexturf102.3105.186.591.5
Omnigrass 41131.9135.1113.5116.3
Omnigrass 5178.986.866.374.1
Sofsport159.2161.9137.5140.2
Sprinturf207.3220.3177.7189.4
Wear3
Astroplay104.6122.390.3105.8
Astroturf314.1327.1265.8275.4
Experimental140.9162.6121.0139.8
Fieldturf152.6190.0132.3164.6
Geoturf189.9207.5163.5178.8
Nexturf111.1114.296.5100.3
Omnigrass 41150.9166.9130.2143.8
Omnigrass 51101.7111.388.396.6
Sofsport180.9195.4156.2168.4
Sprinturf231.4256.2197.4218.3
LSD (p=0.05)21.337.418.431.4

1Grooming of wear and no wear plots occured on 9-10 Oct 2003.
2Severity Index and Head Injury Criterion were measured using a Clegg Impact Tester equipped with a 2.25 kg hammer.
34 Aug testing performed on 4 Aug after wear simulating 44 games. 27 Aug testing performed after wear simulating 84 games.

Microbial colonies isolated from surfaces included a mixture of fungi and bacteria. Colonies from the trash can were predominantly fungi. While not specifically identified, all colonies from the sauna swab appeared to be the same. S. aureus was positively identified from several samples including towels, blocking pads, weight equipment, and the stretching table. In addition, S. aureus was positively identified from every facial and hand swabs tested.

References

  • Baird-Parker, AC. 1990. The staphylococci: an introduction. Pg 1S-8S In: Journal of Applied Bacteriology Symposium Supplement Series 19. D. Jones, R G Board, and M Sussman, ed. Blackwell Scientific Publications. Oxford.
  • Begier, E.M., K. Frenette, N.L. Barrett, P. Mshar, S. Petit, D.J. Boxrud, K Watkins-Colwell, S. Wheeler, E.A. Cebelinski, A. Glennen, D. Nguyen, and J.L. Hadler. 2004. A high-morbidity outbreak of methicillin-resistant Staphylococcus aureus among players on a college football team, facilitated by cosmetic body shaving and turf burns. Clin Infect Dis 39: 1446-1453.
  • Bennet, R.W. and G.A. Lancette. 1998. Bacteriological Analytical Manual, 8th Edition, Revision A. Chapter 12.
  • Essers, L. and K. Radebold. 1980. Rapid and reliable identification of Staphylococcus aureus by a latex agglutination test. J. Clin. Microbiol. 12:641-643.
  • Kazakova, S.V., J.C. Hageman, M. Matava, A. Srinivasan, L. Phelan, B. Garfinkel, T. Boo, S. McAllister, J. Anderson, B. Jensen, D. Dodson, D. Lonsway, L.K. McDougal, M. Arduino, V.J. Fraser, G. Killfore, F.C. Tenover, S. Cody, and D.B. Jernigan. 2005. A clone of methicillin-resistant Staphylococcus aureus among professional football players. NEJM 352:468-475.
  • Marples, R.R., J.F. Richardson, and F.E. Newton. 1990. Staphylococci as part of the normal flora of human skin. Pg 93S-99S In: Journal of Applied Bacteriology Symposium Supplement Series 19: Staphylococci. D. Jones, R G Board, and M Sussman, ed. Blackwell Scientific Publications. Oxford.
  • McNitt, A.S. 2005. Synthetic Turf in the USA -- Trends and Issues. Int. Turfgrass Soc. Res. J. 10:27-33.
  • Seppa, N. 2005. There's the rub: Football abrasions can lead to nasty infections. Science News 167: 85-86.

Temperature and Color

Temperature

Researchers have found that the surface temperatures of synthetic turf playing surfaces are significantly higher than natural turfgrass surfaces when exposed to sunlight. (Buskirk et al., 1971; Koon et al., 1971; and Kandelin et al. 1976). Buskirk et al. (1971) found that the surface temperatures of traditional synthetic turf were as much as 35-60 °C higher than natural turfgrass surface temperatures. Buskirk et al. (1971) placed thermocouples on the inner soles of cleated shoes and had individuals walk on the synthetic surface to determine the amount of heat transferred directly from the surface to the individual's foot. Any heat gain to the foot must be dissipated by blood flow. Buskirk et al. (1971) concluded that the heat transfer from the surface to the sole of an athlete's foot was significant enough to contribute to greater physiological stress that may result in serious heat related health problems.

Surface temperatures of infill synthetic turf systems have been reported to be as high as 93°C on a day when air temperatures were 37°C (Brakeman, 2004). Researchers at Brigham Young University measured the surface and air temperature above an infill synthetic turf system before and for a period of time after water had been applied through irrigation (Brakeman, 2004). The researchers reported that after 30 minutes of irrigation the surface temperature was lowered to that of a nearby natural turfgrass surface (29°C). However, the researchers reported that the surface temperature rose very quickly and within 5 minutes had risen to 49°C. This rapid rise in temperature could be due to the lack of through wetting of the infill media, which was found to be hydrophobic. This author personally observed this field on 19 May 2004. The infill media was very hydrophobic and water was observed to bead-up and run over the surface rather than penetrate. After a 10-minute irrigation cycle, water was observed to be moving laterally over the surface while the infill media was only wet to an average depth of 1 - 2 mm. The use of a non-ionic wetting agent may help to alleviate this problem.

Morehouse (1992) suggests that the evaporation of 1.2 L m -2 h -1 of water should be sufficient to cool a traditional synthetic surface to a level near that of a natural turfgrass surface and notes that water routinely applied to synthetic surfaces, used for women's field hockey to slow ball bounce, will dampen the surface for at least one-half game even under favorable evaporative conditions (i.e. elevated air temperature and brisk air movement). The amount of water suggested for application prior to a field hockey event is 8,000 to 10,000 L spread evenly across a 105 m x 64 m surface. In our current study, we have observed that after equal quantities of irrigation were applied to the treatment plots, the traditional synthetic turf (Astroturf) remained damp for a longer period of time than nine infill synthetic turf systems. These results indicate that the formula Morehouse (1992) suggested for water application to traditional synthetic turf may not be applicable to infill systems.

We tried to measure the temperature of the synthetic turf surfaces on clear bright days. In central Pennsylvania they are sometimes few and far between. We measured both air and surface temperature using an infrared thermometer (Scheduler Model 2 LiCor Corporation) (Fig. 27).

The temperature results are shown in Tables 19, 20A, and 20B. Some surfaces registered slightly higher in surface temperature compared to others although we found few meaningful air temperature differences three feet above the surfaces.

Table 19. Surface temperature of ten synthetic turf products in 2003.
TreatmentSurface temperature (°F)1Air temperature (°F)2
No Wear
Astroplay116.278.1
Astroturf125.478.6
Experimental119.176.6
Fieldturf116.279.0
Geoturf127.679.7
Nexturf124.077.2
Omnigrass 41118.678.6
Omnigrass 51120.679.3
Sofsport121.880.6
Sprinturf113.779.5
Wear3
Astroplay111.478.1
Astroturf125.279.0
Experimental117.977.2
Fieldturf120.279.2
Geoturf124.779.2
Nexturf122.576.3
Omnigrass 41115.378.8
Omnigrass 51118.279.7
Sofsport120.979.5
Sprinturf107.679.9

1Surface temperature was measured on 7 Sep 2003 using a LiCor Scheduler infrared thermometer.
2Air temperature was measured approximately three feet above synthetic turf surface at the same time surface temperature was measured.
3Plots exposed to wear simulating 88 games at the time of data collection.

Table 20A. Surface and air temperatures (C)¹ of ten synthetic turf products measured at 3 dates in 2003 and 2004.
Product7 Sep 0330 Jun 043 Aug 04
SurfaceAir2SurfaceAirSurfaceAir
Astroplay46.825.651.925.759.530.5
Astroturf51.925.952.425.553.828.9
Experimental48.424.852.326.158.430.8
Fieldturf46.826.158.125.664.828.3
Geoturf53.126.561.125.970.829.5
Nexturf51.125.156.425.171.530.6
Omnigrass 4148.125.953.225.864.229.3
Omnigrass 5149.226.355.625.663.129.4
Sofsport49.927.054.625.562.629.1
Sprinturf45.426.448.125.854.430.0

1Temperatures were measured using a LiCor Scheduler infrared thermometer.
2Air temperature was measured approximately three feet above the synthetic turf surface at the same time surface temperature was measured.

Table 20B. Surface and air temperatures (F)¹ of ten synthetic turf products measured at 3 dates in 2003 and 2004.
Product7 Sep 0330 Jun 043 Aug 04
SurfaceAir2SurfaceAirSurfaceAir
Astroplay116.278.1125.478.3139.186.9
Astroturf125.478.6126.377.9128.884.0
Experimental119.176.6126.179.0137.187.4
Fieldturf116.279.0136.678.1148.682.9
Geoturf127.679.7142.078.6159.485.1
Nexturf124.077.4133.577.2160.787.1
Omnigrass 41118.678.6127.878.4147.684.7
Omnigrass 51120.679.3132.178.1145.684.9
Sofsport121.880.6130.177.9144.784.4
Sprinturf113.779.5118.678.4129.986.0

1Temperatures were measured using a LiCor Scheduler infrared thermometer.
2Air temperature was measured approximately three feet above the synthetic turf surface at the same time surface temperature was measured.

During 2004 and in 2005 we evaluated the effect of irrigation on surface temperatures. Approximatly 0.5 inches of water was applied during irrigation. The application of water significantly lowered the surface temperatures of all synthetic surfaces (Fig. 28 and 29). The temperatures rebounded somewhat after 15 minutes and then remained relatively stable for 90 and 210 minutes, respectively. There were intermittent cumulus clouds during the rating period for these days. The effect of the passing clouds can be seen in the erratic nature of the data especially at the 2 Aug 04 rating date. For this reason, we've included data from our first rating date in 2005 (Fig. 30) that was collected on a very clear day. Air temperatures were not as high as the previous rating dates. We began collecting data on 2 Jun 05 at 11:15 am. Air temperature was 73°F with 39% relative humidity and wind speed was 4-5 mph. Data collection ended at about 3:15 pm at which time air temperature was 80°F with 33% relative humididty and wind speed at 4-5 mph. Because of the almost complete lack of cloud cover, we have more confidence in the 2005 results.


Figure 28. Surface temperatures of synthetic turf plots during and after an irrigation event on 30 June 04


Figure 29. Surface temperatures of synthetic turf plots during and after an irrigation event on 3 August 04.


Figure 30. Surface temperatures of synthetic turf plots during and after an irrigation event on 2 June 05.

Irrigation again resulted in a reduction of surface temperatures for the 195 minutes measured. At the end of the experiment the surface temperatures of the irrigated plots averaged 14 degrees lower than the non-irrigated plots. The Astroturf treatment had the highest pre-irrigation temperature and consistently measured lowest in post-irrigation temperature. This trend can be observed in the 2004 data.

Temperature of a synthetic surface will depend on numerous variables. The benefit of surface cooling through irrigation may vary depending on conditions. Irrigation systems on synthetic fields have other benefits such as reduction of wear by allowing the field manager to broom the surface when wet and wash in fabric softeners and/or wetting agents. More temperature data is being collected and this report will be updated.

Color

In order to determine the amount of matting that is occurring, color readings of the surfaces were recorded on the no wear plots at installation and on the wear plots just prior to grooming on 8 Oct 2003 using a Model CR-310 chromameter (Minolta Co, Ltd, Ramsey, NJ) (Fig. 31). The two measurements should provide the extremes of matting and by measuring color weekly during 2004 we should be able to produce a matting index.

Color data is shown in Table 21. Color data is being collected in an attempt to develop a measure of 'matting' or how much the pile lays over after simulated traffic. We measured color of the wear and no wear plots just before and just after grooming. We had hoped that these measurements would define the spectrum of color differences due to matting. We are not satisfied that this method accurately measures the amount of matting. Currently, we are unaware of an accepted method to quantitatively evaluate matting other than visual ratings.

Table 21. Color (lightness, chroma, and hue angle) of ten synthetic turf products determined in 2003 by the Minolta CR-310 Chroma Meter prior to and after grooming¹
Treatment7 October23 October
Lightness2Chroma3Hue angle4LightnessChromaHue angle
No Wear
Astroplay25.217.0125.726.617.7127.1
Astroturf33.218.4156.833.518.7157.8
Experimental30.917.1127.529.517.3129.2
Fieldturf28.316.7126.828.317.7127.5
Geoturf29.816.5128.930.517.4130.3
Nexturf25.014.5128.225.115.4130.0
Omnigrass 4128.417.6112.728.819.4114.4
Omnigrass 5128.118.3112.527.818.6114.8
Sofsport30.817.4127.630.317.8129.1
Sprinturf28.519.4126.328.720.3127.7
Wear5
Astroplay31.715.4125.530.517.2127.2
Astroturf33.117.5157.333.618.5157.4
Experimental33.316.2127.232.117.6128.7
Fieldturf31.616.4126.831.817.7127.3
Geoturf30.515.6129.230.217.0130.4
Nexturf28.215.4127.327.015.3128.2
Omnigrass 4134.618.3112.035.220.3113.6
Omnigrass 5136.118.2112.334.820.9114.1
Sofsport32.816.7127.530.918.2128.5
Sprinturf33.019.5126.031.120.3127.2
LSD (p=0.05)1.71.20.71.21.30.8

1Grooming of wear and no wear plots occured on 9-10 Oct 2003.
2Expressed on a scale of 0 = black to 100 = white.
3Expressed on a scale of 0 = gray to 60.
4Hue angles of the four primary colors are red, 0°; yellow, 90°; green, 180°; and blue, 270°.
57 Oct and 23 Oct testing were performed after wear simulating 92 games.

Table 22. Color (lightness, chroma, and hue angle) of ten synthetic turf products determined in 2004 by the Minolta CR-310 Chroma Meter prior to and after grooming¹.
Treatment28 July10 August
Lightness2Chroma3Hue angle4LightnessChromaHue angle
No Wear
Astroplay28.818.1125.329.117.0124.5
Astroturf29.417.5157.532.818.4157.5
Experimental31.616.8127.030.816.1126.8
Fieldturf30.617.1126.329.217.4125.7
Geoturf30.316.3128.730.815.8127.1
Nexturf26.515.2128.027.014.9125.9
Omnigrass 4131.118.9112.231.418.8110.3
Omnigrass 5131.018.9111.731.518.6110.3
Sofsport31.217.3127.831.317.6126.7
Sprinturf30.718.8125.231.019.1124.8
Wear5
Astroplay33.015.9124.831.015.7124.3
Astroturf28.717.5157.033.817.3156.6
Experimental33.416.2126.732.916.5126.3
Fieldturf33.116.1126.631.516.6125.7
Geoturf31.315.8128.430.915.8127.0
Nexturf26.914.7126.826.414.1125.7
Omnigrass 4135.918.0111.634.818.2110.0
Omnigrass 5136.418.3111.334.518.3109.7
Sofsport31.716.6127.331.016.6126.4
Sprinturf31.518.1125.331.517.1124.6
LSD (p=0.05)1.21.11.11.51.20.5

1Grooming of wear and no wear plots occured on 4-5 Aug 2004.
2Expressed on a scale of 0 = black to 100 = white.
3Expressed on a scale of 0 = gray to 60.
4Hue angles of the four primary colors are red, 0°; yellow, 90°; green, 180°; and blue, 270°.
528 Jul and 10 Aug testing were performed after wear simulating 92 games.

Summary and Considerations

It should be remembered that the data posted in this report is from the first two years of a long term study. To this point the systems are performing very well. The infill systems are softer, less abrasive, and generally exhibit better traction qualities than traditional Astroturf. They maintained these qualities after 180 plus games of simulated traffic. The Gmax and traction values obtained from the synthetic surfaces are very comparable and in some cases more desirable than those measured on a similarly worn natural turfgrass area.

A review of current literature regarding safety and playability of infill synthetic turf systems can be found in the Athlete Performance and Safety section of this website. For the results of a survey of microbial populations in synthetic turf, please refer to A Survey of Microbial Populations in Infilled Synthetic Turf Fields found on this site.

Some things to consider when budgeting for an infilled synthetic turf system:

  1. Poor surface grading and lack of internal drainage are the two main construction problems encountered in infill synthetic turf systems in the USA. Currently, there are no standard specifications for drainage gravel installed beneath the backing of an infill system. The lack of an agreed upon standard has resulted in numerous installations with poor quality gravel that is either hard to grade to desired tolerances or that allows little internal drainage after compaction. The Synthetic Turf Council was formed in 2002 in order to produce a set of minimum specifications that will protect consumers from installations of poor quality synthetic turf infill systems (Synthetic Turf Council Inc., 2003). Currently, the council specifies that the sub-base drainage gravel of a synthetic turf field should provide adequate drainage and stability; however, a gravel particle size distribution is not specified. Subcommittees within the Synthetic Turf Council and in the F.08 division of ASTM are currently working on sub-base gravel specifications. The following link is to a set of specifications that have worked well. Gravel Drainage Specifications. By no means does this suggest that other drainage aggregates that do not meet this specification will cause drainage failure. They are listed here only as a guide. University and private labs can test drainage material to make sure they have sufficient permeability after compaction. After suitable materials are located, a quality control program during shipping is strongly suggested. The specifications provided are based on the specifications for drainage beneath a USGA golf green. These specifications suggest quality control testing of the gravel every 500 tons.
  2. For heavily used fields, such as a high school where there is at least one sporting event per day, you should plan to broom the field weekly. This is done to keep the pile somewhat upright. This is different from grooming where the granules are loosened. Brooming can be accomplished by dragging a set of tennis court brooms or a piece of traditional Astroturf turned upside down across the field in varying directions. To reduce abrasion due to brooming, drag the tennis court brooms or Astroturf when the field is wet. Do not use a power broom weekly as this aggressive brooming will increase wear to the pile fiber due to abrasion.
  3. Grooming or loosening of the infill granules should be done at least once or twice per year. See the section on simulated foot traffic and grooming for details. Most field managers that we've talked to do not like the spring tine method of loosening infill because they feel it is too aggressive. Most like the star shaped unpowered slicer that we used (Fig. 32) and suggest a similar but larger model for field use. (Fig.33) See simulated foot traffic and grooming for details. Currently we suggest loosening the granules twice per year.
    Figure 32 and 33
  4. The fields do get hot on sunny days. Some organizations have installed irrigation systems to reduce the heat. These fields warm up fast on clear sunny days but also cool down rapidly when the sun is not shining; there doesn't seem to be much of a heat sink. Irrigation of these fields dramatically reduce the surface temperature; however, in our limited testing we have found that a dramatic reduction in temperature is short term. Irrigation resulted in an average 15 degree F decrease in surface temperature for 200 minutes in our conditions. While irrigation may have a dramatic affect on surface temperature for a limited time and a limited effect over a longer time, it may prove beneficial in other respects such as washing in fabric softeners and wetting agents. Irrigation would also be beneficial in wetting the surface prior to brooming to reduce abrasive wear on the pile fibers. While these surfaces are hotter than natural turfgrass, the temperatures measured in this study of non-irrigated surfaces do not exceed traditional synthetic turf (Astroturf) that has been in use since the 1960s.
  5. There is a static build up on these surfaces, at least in year one when the fields are new. The only problem that I see with the static is aesthetic. The black granules tend to stick to the upright pile fibers and the field will temporarily look darker in high wear areas. The application of very dilute fabric softener will reduce this problem and has become a standard practice for some field managers. We have no data on the use of fabric softeners and their effect on playability. Some field managers have expressed their opinion that if fabric softener is used, it should be sprayed several days prior to an event as the material can make the field slippery if applied just prior to a game. Static tends to be a problem only with new systems. As the systems age the static is reduced; however, a new problem can arise--hydrophobicity. The granulated infill media in many systems can become hydrophobic. Precipitation will 'beadup' and roll off the surface rather than penetrate. An application of a wetting agent or surfactant may be required to maintain permeability over time. The effectiveness of wetting agents for this application has not been tested but in theory they should reduce the hydrophobicity of the infill media.
  6. The long-term durability of these fields is unknown. The duration of the warranties offered by synthetic turf companies has been set by economic and competitive issues as opposed to knowledge of the long-term durability of the systems. Originally, the standard warranty of a crumb rubber infill synthetic turf system was five years. Competition increased the warranty to eight years and for several projects the systems were warranted for 10 years. Currently, an eight-year warranty is considered standard in the United States. This author has seen some outdoor high-use fields that may last well beyond the warranty period while others look worn after only one year of use. Since the pile fibers breakdown due to both foot traffic and photodegradation, indoor fields will typically outlast fields that are exposed to sunlight. The author has observed thinning pile fiber in high wear areas around the goal mouth of high school lacrosse fields after only two years of use. There is no standard method to evaluate wear or thinning of the pile fiber. A warranty providing a guarantee against 'excessive wear' is open to interpretation.

The Synthetic Turf Council (Daulton, GA) is a non-profit organization formed to set minimum quality standards for synthetic turf manufacturing and use in the United States. The council is currently wrestling with the issue of warranty duration and is considering suggesting some guidelines on system warranties (Synthetic Turf Council, Inc., 2003). Of critical importance to the consumer when trying to select an infill system is to consider whether that company will still be in business throughout the duration of the warranty. Some of the companies representing an infill synthetic turf system have already gone out of business in the United States. Of considerable note was the closure of SRI, Inc., owner and manufacturer of AstroTurf, AstroPlay, and NeXturf. From the 1970's through much of the 1990's this company was the largest manufacturer and installer of synthetic turf systems in the United States.

In the bid contract:

  • Demand that the surface company pay for independent Gmax testing yearly for the length of warranty.
  • Negotiate a maximum acceptable Gmax level lower than 200 (175 suggested)
  • Demand good quality grooming equipment be provided.
  • You'll also need a utility cart to pull the grooming equipment.

In conclusion we've made progress establishing testing methods for evaluation of these surfaces. This will allow us to more collect data more rapidly in the coming years. The infill systems generally outperformed traditional Astroturf in playing quality. The playing quality of these systems remained high after rather intense simulated traffic was applied. The playing quality of the infilled systems increased after brooming and grooming.

Bibliography and Acknowledgements

  • American Society for Testing and Materials. 2000a. Annual Book of ASTM Standards. Vol. 15.07. End Use Products. Standard Test Method for Shock-Absorbing Properties of Playing Surface Systems and Materials. F355-95 Procedure A. ASTM, West Conshohocken, PA.
  • American Society for Testing and Materials. 2000b. Annual Book of ASTM Standards. Vol. 15.07. End Use Products. Standard Test Method for Shock-Attenuation Characteristics of Natural Playing Surface Systems Using Lightweight Portable Apparatus. F1702-96. ASTM, West Conshohocken, PA.
  • American Society for Testing and Materials. 2000c. Annual Book of ASTM Standards. Vol. 15.07. End Use Products. Proposed Standard Test Method for Traction Characteristics of the Athletic Shoe - Sports Surface Interface. Work Number 486. ASTM, West Conshohocken, PA.
  • American Society for Testing and Materials. 2000d. Annual Book of ASTM Standards. Vol. 15.07. End Use Products. Shock-Absorbing Properties of North American Football Field Playing Systems as Measured in the Field. F1936-98. ASTM, West Conshohocken, PA.
  • American Society for Testing and Materials. 2000e. Annual Book of ASTM Standards. Vol. 15.07. End Use Products. Standard Test Method Relative Abrasiveness of Synthetic Turf Playing Surfaces. F1015-86. ASTM, West Conshohocken, PA.
  • Bowers, K.D.J. and Martin, R.B. 1975 Cleat-surface friction on new and old AstroTurf. Med Sci Sports, 7:132-135.
  • Brakeman, L. 2004. Infill systems spark debate at STMA conference.
  • Buskirk, E.R., E.R. McLaughlin, and J.L. Loomis. 1971. Microclimate over artificial turf. J. Health, Phys. Ed., Rec. 42(9):29-30.
  • Cameron, B. and Davis, O. 1973. The swivel football shoe: a controlled study. Am. J. Sports Medicine 16-27.
  • Clarke, K. and Miller, S. 1977. Turf related injuries in college football and soccer. Athletic Training 12(1): 28-32.
  • Cockerham, S.T. and D.J. Brinkman. 1989. A simulator for cleated-shoe sports traffic on turfgrass research plots. California Turfgrass Culture 39(3&4):9-10.
  • Cole, G.K., Nigg, B.M., Fick, G.H., and Morlock, M. 1995. Internal loading of the foot and ankle during impact in running. J. Applied Biomechics. 11:25-46.
  • Culpepper, M. and Morrison, T. 1987. High school football game injuries from four Birmingham municipal fields. Alabama J. Med. Sci. 24(4): 378-382.
  • Heidt, R.S.J., Dormer, S.G., Cawley, P.W., Scranton, P.E.J., Losse, G., and Howard, M. Differences in friction and torsional resistance in athletic shoe-turf surface interfaces. Am J Sports Medicine, 24:834-842, 1996.
  • Henschen, K., Hell, J., Bean, B., and Crain S. 1989. Football injuries: is astroturf or grass the culprit? Utah J. HPERD 21:5-6.
  • Kandelin, W.W., G.S. Krahenbuhl, G.S. Schact, and C.A. Schact. 1976. Athletic field microclimates and heat stress. J. Safety Res. 8:106-111.
  • Koon, J.L., E.W. Rochester, and M.K. Howard. 1971. Environmental studies with artificial turf and grass surfaces. In Am. Soc. Agric. Eng., Pullman, WA. 27-31 June.
  • Krahenbuhl, G.S. 1974. Speed of Movement with Varying Footwear Conditions on Synthetic Turf and Natural Grass. Res. Quarterly 45(1):28-33.
  • Lambson, R.B., Barnhill, B.S. and Higgins, R.W. 1999. Football cleat design and its effects on anterior cruciate ligament injuries. A three year prospective study. Am J. Sports Medicine, 24 (2): 155-159.
  • Martin, B.R. 1990. Problems Associated with Testing the Impact Absorption Properities of Artificial Playing Surfaces. Natural and Artificial Playing Fields: Characteristics and Safety Features, ASTM STP 1073, R.C. Schmidt, E.F. Hoerner, E.M. Milner, and C.A. Morehouse, Eds., American Society for Testing and Materials, Philadelphia, pp. 77-84.
  • Meyers, M.C. and B.S. Barnhill. 2004. Incidence, Causes, and Severity of High School Football Injuries on FieldTurf Versus Natural Grass. Am J. Sports Medicine 32 (7): 1626-1638.
  • McNitt, A. S., Middour R. O. and Waddington D. V. 1997. Development and evaluation of a method to measure traction on turfgrass surfaces. Journal of Testing and Evaluation 25:99-107.
  • McNitt, A.S., and D.M. Petrunak. 2001. Playing surface quality of an infilled synthetic turf system. 2001 Annual Research Report: The Pennsylvania State University Center for Turfgrass Science. pp. 30-35.
  • McNitt, A. S., Landschoot, P. J. and Petrunak D. M. 2004. Evaluation of the Playing Surface Hardness of an Infilled Synthetic Turf System. Acta Hort. (ISHS) 661:559-563.
  • Morehouse, C.A. 1992. Artificial Turf. In D.V. Waddington et al. (eds). Turfgrass - Agromomy Monograph No. 32. Am. Soc. Agron., Madison, WI. pp. 89 - 127.
  • Morehouse, C.A., and W.E. Morrison. 1975. The artificial turf story: A research review. Penn State HPER Ser. No. 9. College of Health, Physical Education and Recreation, Penn State Univ., University Park, PA.
  • National Collegiate Athletic Association. 2004. NCAA Injury Surveillance System [Online].
  • Nigg, B.M. 1997. Impact forces in running. Current Opinion in Orthopedics. 8:43-47.
  • Nigg, B.M. and Segesser, B. 1988. The influence of playing surfaces on the load of the locomotor system and on injuries for football and tennis. Sports Medicine. 5:375-385.
  • Popke, M. 2002. Shock Value. Athletic Business Magazine. Sept. pp. 54-66.
  • Powell, J. W. and Schootman M. 1993. A multivariate risk analysis of natural grass and AstroTurf playing surfaces in the National Football League. Int. Turfgrass Soc. Res. J. 7:201-221.
  • Powell, J. W. and Schootman, M. 1992. A multivariate risk analysis of selected playing surfaces in the National Football League: 1980 to 1989. Am. J. Sports Medicine, 20:686-694.
  • Shorten, M. and Himmelsbach, J. 2002. Traction of cleated shoes on natural and artificial turf football surfaces. Report to sponsors. biomechanica.com. 46 pp.
  • Shorten M.R., B. Hudson, and J.A. Himmelsbach. 2003. Shoe-Surface Traction of Conventional and In-filled Synthetic Turf Football Surfaces. In P. Milburn et al. (Eds.) Proc XIX International Congress of Biomechanics, University of Otago, Dunedin, New Zealand.
  • Skovron, M., Levy, I., and Agel, J. 1990. Living with artificial grass: a knowledge update. Am. J. Sport Medicine, 18(50):510-512.
  • Stefanyshyn, D.J., J. Worobets, and B.M. Nigg. 2002. Properties of infilled artificial playing surfaces. A project report for Cannon Johnston Sport Architecture. Human Performance Laboratory, The University of Calgary, Calgary, Alberta, Canada.
  • Synthetic Turf Council Inc. 2003. Guidelines for the essential elements of synthetic turf specifications. Synthetic Turf Council Inc. Daulton GA. USA. 26 pp.
  • Torg, J.S., Quedenfeld, T.C., and Landau, S. 1978. The shoe-surface interface and its relationship to football knee injuries. J Sports Med, 2:261-269, 1974.
  • Valiant, G.A. 1990. Traction Characteristics of Outsoles for Use on Artificial Playing Surfaces. Natural and Artificial Playing Fields: Characteristics and Safety Features, ASTM STP 1073, R.C. Schmidt, E.F. Hoerner, E.M. Milner, and C.A. Morehouse, Eds., American Society for Testing and Materials, Philadelphia, pp. 61-68.
  • Zemper, E.D. 1989. Injury rates in a national sample of college football teams: A two year prospective study. Physician and Sports Medicine Feb 1989.

Acknowledgements

The researchers for this project would like to thank the following companies and organizations for their support. Without their continued support this project would be impossible to complete.

Athlete Performance and Safety

Numerous studies have been conducted to evaluate the safety and playability of traditional (non-infill) synthetic turf surfaces. Three methodologies are used to compare the safety and performance of various surfaces. These include 1) material tests where mechanical devices simulate human movement and measure the associated forces; 2) human performance tests where researchers measure the forces associated with the interaction of a human subject and a surface; and 3) epidemiological studies in which the number and type of injuries sustained by athletes during actual sporting events are counted.

Material tests have been completed that measure the shoe-surface traction and surface hardness of synthetic turf surfaces (Bowers and Martin, 1975; McNitt and Petrunak, 2001; Valiant, 1990). Human subject tests have shown improved athlete performance on traditional synthetic turf when compared to natural turfgrass (Krahenbuhl, 1974; Morehouse and Morrison, 1975) and epidemiological studies have counted the number of knee and ankle injuries on synthetic versus natural turfgrass (Meyers and Barnhill, 2004; Powell and Schootman, 1992; Powell and Schootman, 1993).

No large-scale epidemiological studies have been published comparing the number of surface-related injures sustained by athletes playing on infill synthetic turf systems to the number of injures sustained on either traditional synthetic turf or natural turfgrass surfaces. One study (Meyers and Barnhill, 2004) compared injury incidence of eight high school (American) football teams in Texas USA playing on infilled synthetic surfaces (FieldTurf) and natural turfgrass surfaces. Although similarities in injury occurrence existed between FieldTurf and natural grass fields over a five-year period of competitive play, there were significant differences in injury time loss, injury mechanism, anatomical location of injury, and type of tissue injured between playing surfaces. The researchers reported higher incidences of 0-day time loss injuries, noncontact injuries, surface/epidermal injuries, muscle-related trauma, and injuries during higher temperatures on FieldTurf compared to natural turfgrass surfaces. Higher incidences of 1- to 2-day time loss injuries, 22+ day time loss injuries, head and neural trauma, and ligament injuries were recorded on natural turfgrass fields compared to FieldTurf. The researchers state a number of limitations to their study including the random variation in injury typically observed in high-collision team sports and the percentage of influence from risk factors, other than simply surface type. Field conditions at the time of injury were not measured although the researchers noted that the majority of injuries (84.4%) occurred on natural turfgrass surfaces under conditions of no precipitation (dry surface).

The United States National Collegiate Athletic Association (NCAA) is collecting injury data from numerous men's and women's sporting events across the United States using a computerized system called " NCAA Injury Surveillance System" (National Collegiate Athletic Association, 2004) but presently does not have sufficient data from which to draw conclusions (R. Dick, 2004, personal communication).

Stefanyshyn et al. (2002) used human performance comparisons to evaluate 20 configurations of infill synthetic turf systems. Human subjects performed various maneuvers on the surfaces and the forces associated with the cleated foot interacting with the surface were recorded in the laboratory using a force plate installed beneath the turf surface. Stefanyshyn et al. (2002) reported a significant range of traction and surface hardness differences among the infill synthetic surfaces (Table 1) and grouped the 20 infill surfaces into categories of highly recommended, recommended, and not recommended based on surface hardness and both the rotational and translational (linear) traction recorded on these surfaces.

Shorten et al. (2003) performed material tests in which weighted shoes were dragged across varying infill synthetic turf systems and traditional synthetic turf. The translational and rotational traction of the various shoe-surface combinations were measured. The researchers concluded that both shoes and surfaces significantly affect traction. On all surfaces tested, shoes with lower profile cleats or studs had better overall traction performance compared to shoes with longer cleats and infill systems had better traction performance than traditional synthetic turf. Traction performance was calculated using an index where rotational traction values were subtracted from translational traction values. To eliminate scaling and range differences between the translational and rotational resistance measures, calculations were done using "standard scores" rather than raw data. The standard score is a measure of where a particular result lies relative to the average and distribution of all the results recorded: ex. Standard Score = (Actual Score − Average Score) / (Standard Deviation of All Scores). The researchers stated that further research is required to determine the effects of moisture, temperature and aging on surface traction performance. Both the study by Stefanyshyn et al. (2002) and the study by Shorten et al. (2003) were performed on newly constructed infill systems in a laboratory setting.

By Andrew McNitt and Dianne Petrunak

Gravel Drainage Specifications

Numerous studies have been conducted to evaluate the safety and playability of traditional (non-infill) synthetic turf surfaces. Three methodologies are used to compare the safety and performance of various surfaces. These include 1) material tests where mechanical devices simulate human movement and measure the associated forces; 2) human performance tests where researchers measure the forces associated with the interaction of a human subject and a surface; and 3) epidemiological studies in which the number and type of injuries sustained by athletes during actual sporting events are counted.

Material tests have been completed that measure the shoe-surface traction and surface hardness of synthetic turf surfaces (Bowers and Martin, 1975; McNitt and Petrunak, 2001; Valiant, 1990). Human subject tests have shown improved athlete performance on traditional synthetic turf when compared to natural turfgrass (Krahenbuhl, 1974; Morehouse and Morrison, 1975) and epidemiological studies have counted the number of knee and ankle injuries on synthetic versus natural turfgrass (Meyers and Barnhill, 2004; Powell and Schootman, 1992; Powell and Schootman, 1993).

No large-scale epidemiological studies have been published comparing the number of surface-related injures sustained by athletes playing on infill synthetic turf systems to the number of injures sustained on either traditional synthetic turf or natural turfgrass surfaces. One study (Meyers and Barnhill, 2004) compared injury incidence of eight high school (American) football teams in Texas USA playing on infilled synthetic surfaces (FieldTurf) and natural turfgrass surfaces. Although similarities in injury occurrence existed between FieldTurf and natural grass fields over a five-year period of competitive play, there were significant differences in injury time loss, injury mechanism, anatomical location of injury, and type of tissue injured between playing surfaces. The researchers reported higher incidences of 0-day time loss injuries, noncontact injuries, surface/epidermal injuries, muscle-related trauma, and injuries during higher temperatures on FieldTurf compared to natural turfgrass surfaces. Higher incidences of 1- to 2-day time loss injuries, 22+ day time loss injuries, head and neural trauma, and ligament injuries were recorded on natural turfgrass fields compared to FieldTurf. The researchers state a number of limitations to their study including the random variation in injury typically observed in high-collision team sports and the percentage of influence from risk factors, other than simply surface type. Field conditions at the time of injury were not measured although the researchers noted that the majority of injuries (84.4%) occurred on natural turfgrass surfaces under conditions of no precipitation (dry surface).

The United States National Collegiate Athletic Association (NCAA) is collecting injury data from numerous men's and women's sporting events across the United States using a computerized system called " NCAA Injury Surveillance System" (National Collegiate Athletic Association, 2004) but presently does not have sufficient data from which to draw conclusions (R. Dick, 2004, personal communication).

Stefanyshyn et al. (2002) used human performance comparisons to evaluate 20 configurations of infill synthetic turf systems. Human subjects performed various maneuvers on the surfaces and the forces associated with the cleated foot interacting with the surface were recorded in the laboratory using a force plate installed beneath the turf surface. Stefanyshyn et al. (2002) reported a significant range of traction and surface hardness differences among the infill synthetic surfaces (Table 1) and grouped the 20 infill surfaces into categories of highly recommended, recommended, and not recommended based on surface hardness and both the rotational and translational (linear) traction recorded on these surfaces.

Shorten et al. (2003) performed material tests in which weighted shoes were dragged across varying infill synthetic turf systems and traditional synthetic turf. The translational and rotational traction of the various shoe-surface combinations were measured. The researchers concluded that both shoes and surfaces significantly affect traction. On all surfaces tested, shoes with lower profile cleats or studs had better overall traction performance compared to shoes with longer cleats and infill systems had better traction performance than traditional synthetic turf. Traction performance was calculated using an index where rotational traction values were subtracted from translational traction values. To eliminate scaling and range differences between the translational and rotational resistance measures, calculations were done using "standard scores" rather than raw data. The standard score is a measure of where a particular result lies relative to the average and distribution of all the results recorded: ex. Standard Score = (Actual Score − Average Score) / (Standard Deviation of All Scores). The researchers stated that further research is required to determine the effects of moisture, temperature and aging on surface traction performance. Both the study by Stefanyshyn et al. (2002) and the study by Shorten et al. (2003) were performed on newly constructed infill systems in a laboratory setting.

Selection and Placement of Materials When the Intermediate Layer Is Used

The tables above describe the particle size requirements of the gravel and the intermediate layer material.

The intermediate layer shall be spread to a uniform thickness of two to four inches (50 to 100 mm) over the gravel drainage blanket (e.g., if a 3-inch depth is selected, the material shall be kept at that depth across the entire area), and the surface shall conform to the contours of the proposed finished grade.

Selection of Gravel

Selection of this gravel is based on the particle size distribution of the intermediate layer material. The construction superintendent must work closely with the soil testing laboratory in selecting the appropriate gravel. Either of the following two methods may be used:

Send samples of different gravel materials to the lab when submitting samples of components for the intermediate layer material. As a general guideline, look for gravel in the 2 mm to 9.5 mm range. The lab first will determine the best intermediate layer material, and then will test the gravel samples to determine if any meet the guidelines outlined below.

Submit samples of the components for intermediate layer material, and ask the laboratory to provide a description, based on the intermediate layer material tests, of the particle size distribution required of the gravel. Use the description to locate one or more appropriate gravel materials, and submit them to the laboratory for confirmation.

It is not necessary to understand the details of these recommendations; the key is to work closely with the soil testing laboratory in selecting the gravel. Strict adherence to these criteria is imperative; failure to follow these guidelines could result in drainage failure.

The criteria are based on engineering principles which rely on the largest 15% of the root zone particles "bridging" with the smallest 15% of the gravel particles. Smaller voids are produced, and they prevent migration of root zone particles into the gravel yet maintain adequate permeability. The D85 (root zone) is defined as the particle diameter below which 85% of the soil particles (by weight) are smaller. The D15 (gravel) is defined as the particle diameter below which 15% of the gravel particles (by weight) are smaller.

  • For bridging to occur, the D15 (gravel) must be less than or equal to eight times the D85 (root zone).
  • To maintain adequate permeability across the root zone/gravel interface, the D15 (gravel) shall be greater than or equal to five times the D15 (root zone).
  • The gravel shall have a uniformity coefficient (Gravel D90/Gravel D15) of less than or equal to 3.0.

Furthermore, any gravel selected shall have 100% passing a ½" (12 mm) sieve and not more than 10% passing a No. 10 (2 mm) sieve, including not more than 5% passing a No. 18 (1 mm) sieve.

2005-2006 Abrasion Data

Abrasion index of ten synthetic turf products prior to and after grooming.1
TreatmentAbrasion Index2
20052006
4 August7-8 September6 July21 September
No Wear
Astroplay37.436.9NRNR
Astroturf57.460.254.860.1
Experimental46.744.0NRNR
Fieldturf36.036.239.938.9
Geoturf52.054.1NRNR
Nexturf36.138.7NRNR
Omnigrass 4138.438.640.841.1
Omnigrass 5134.636.738.040.6
Sofsport40.037.142.845.2
Sprintturf40.543.347.252.7
Wear3
Astroplay36.335.0NRNR
Astroturf53.459.248.253.4
Experimental42.740.4NRNR
Fieldturf36.138.439.539.8
Geoturf45.343.6NRNR
Nexturf36.538.8NRNR
Omnigrass 4139.238.943.443.6
Omnigrass 5137.137.341.740.6
Sofsport37.333.039.642.2
Sprintturf36.137.339.2

45.0

LSD (p=0.05)0.91.23.73.0

1In 2005, grooming of wear and no wear plots occurred on 5 Aug and 9 Aug 2005. In 2006, grooming of wear and no wear plots occurred on 23-24 Aug 2006.
2Abrasion index is determined by pulling foam blocks in a weighted sled across the plots in 4 directions and determining the loss (by weight) of the blocks. Abrasiveness index =[(starting block weight - final block weight)/6] *100.
3Aug testing performed after wear simulating 96 games. 7-8 Sep testing performed after grooming of all plots on 5 and 9 Aug 2005. 6 Jul testing performed after wear simulating 108 games. 21 Sep testing performed after grooming of all plots on 23-24 Aug 2006.
NR = Not Rated in 2006.

2005-2006 Translational Traction Data

Treatment20052006
2 August25 August16 August7 August
Static2Dynamic3StaticDynamicStatic2Dynamic3StaticDynamic
No Wear
Astroplay1.341.141.311.15NRNRNRNR
Astroturf1.511.341.641.381.611.351.551.34
Experimental1.361.051.411.08NRNRNRNR
Fieldturf1.451.171.371.131.471.261.471.22
Geoturf1.361.261.311.23NRNRNRNR
Nexturf1.431.191.391.17NRNRNRNR
Omnigrass 411.401.131.391.151.481.241.481.21
Omnigrass 511.361.191.321.111.441.201.481.31
Sofsport1.361.151.351.141.481.261.461.25
Sprintturf1.291.111.311.091.391.191.381.18
Wear4
Astroplay1.431.231.421.21NRNRNRNR
Astroturf1.691.501.691.471.541.291.441.09
Experimental1.411.181.371.15NRNRNRNR
Fieldturf1.461.211.391.161.491.321.501.28
Geoturf1.331.191.291.14NRNRNRNR
Nexturf1.441.171.391.16NRNRNRNR
Omnigrass 411.491.151.451.091.501.221.511.23
Omnigrass 511.431.181.381.151.471.261.501.30
Sofsport1.431.241.381.161.451.191.421.17
Sprintturf1.321.191.301.121.381.191.381.15
LSD (p=0.05)0.09

0.05

0.090.060.100.070.100.08

1In 2005, grooming of wear and no wear plots occurred on 5 and 9 Aug 2005. In 2006, grooming of wear and no wear plots occurred on 23-24 Aug 2006.
2Static traction = peak amount of force (N) that is normal to the playing surface.
3Dynamic traction = amount of force (N) to maintain linear motion of footwear/amount of force (N) that is normal to the playing surface.
42 August testing performed after wear simulating 96 games. 25 August testing performed after grooming of the plots on 5 and 9 August 2005. 16 August testing performed after wear simulating 108 games. 7 September testing performed after grooming of the plots on 23-24 August 2006.
NR = Not Rated in 2006.

2005-2006 Rotational Traction Data

Rotational traction determined by ASTM traction standard using 237 pounds of vertical force prior to and after grooming.1
TreatmentRotational traction (nm)2
20052006
3 August26 August17 August1 September
No Wear
Astroplay38.240.1NRNR
Astroturf46.247.443.255.7
Experimental37.841.1NRNR
Fieldturf38.142.937.145.1
Geoturf42.742.3NRNR
Nexturf44.847.1NRNR
Omnigrass 4136.842.134.144.7
Omnigrass 5136.741.035.944.6
Sofsport38.741.337.246.8
Sprintturf37.141.338.446.7
Wear3
Astroplay37.740.8NRNR
Astroturf44.654.545.557.6
Experimental37.241.2NRNR
Fieldturf38.847.542.750.0
Geoturf44.346.4NRNR
Nexturf43.945.9NRNR
Omnigrass 4137.042.138.247.7
Omnigrass 5136.440.636.744.2
Sofsport38.347.140.249.7
Sprintturf36.744.037.345.4
LSD (p=0.05)4.44.63.24.4

1In 2005, grooming of wear and no wear plots occurred on 5 and 9 August 2005. In 2006, grooming of wear and no wear plots occurred on 23-24 August 2006.
2Rotational traction.
3August testing performed after wear simulating 96 games. 26 August testing performed after grooming of the plots on 5 and 9 August 2005. 17 August testing performed after wear simulating 108 games. 1 September testing performed after grooming of the plots on 23-24 August 2006.
NR = Not rated in 2006.

2005-2006 Surface Hardness (Gmax) Measured via ASTM Standard F1702

Surface hardness (gmax) of infill systems determined with the Clegg Impact Tester prior to and after grooming.1
Treatment20052006
Gmax2
26 May29 Jul23 Aug19 Sep6 Oct20 Apr6 Jul14 Aug25 Aug26 Sep325 Oct3
No Wear
Astroplay40.339.241.640.642.1NRNRNRNRNRNR
Astroturf94.676.575.677.774.874.067.382.380.4----
Experimental47.246.048.954.953.5NRNRNRNRNRNR
Fieldturf60.456.056.959.663.260.057.162.355.1----
Geoturf71.463.963.065.263.8NRNRNRNRNRNR
Nexturf39.635.436.737.338.8NRNRNRNRNRNR
Omnigrass 4146.747.850.349.451.349.550.649.947.3----
Omnigrass 5134.937.838.438.540.340.142.740.036.9----
Sofsport58.855.058.857.357.856.562.558.558.3----
Sprintturf65.057.565.367.966.762.451.068.366.9----
Wear4
Astroplay48.146.750.249.849.4NRNRNRNRNRNR
Astroturf80.389.187.184.583.678.678.993.890.090.188.5
Experimental51.652.253.060.557.1NRNRNRNRNRNR
Fieldturf68.060.263.667.963.565.166.970.665.581.576.7
Geoturf75.270.371.271.169.7NRNRNRNRNRNR
Nexturf40.840.240.741.242.6NRNRNRNRNRNR
Omnigrass 4153.459.058.958.659.258.062.862.458.768.959.4
Omnigrass 5140.044.845.847.747.049.053.252.345.157.248.0
Sofsport61.161.861.763.062.960.870.263.562.870.871.3
Sprintturf68.969.769.575.171.666.463.877.278.085.686.6
LSD (p=0.05)7.01.41.71.01.33.92.88.63.09.110.6

1Grooming of wear and no wear plots occurred on 5 and 9 Aug 2005.
2Surface hardness was measured using a Clegg Impact Testre equipped with a 2.25 hammer.
3Data Collected in plot ares with extreme wear (in tractor tire tracks).
426 May testing performed prior to any wear in 2005. 29 Jul testing performed after wear simulating 96 games. 23 Aug testing performed after grooming. 19 Sep testing performed after wear simulating 4 games after grooming. 7 Sep testing performed after wear simulating 8 games after grooming. 13 Sep testing performed after wear simulating 8 games after grooming. 13 Sep testing performed after wear simulating 12 games after grooming. 6 Oct testing performed after wear simulating 32 games after grooming. 20 April testing performed prior to any wear in 2006. 6 Jul and 14 Aug testing performed after wear simulating 108 games. 25 Aug testing performed after grooming.
NR = Not Rated in 2006.

2005-2006 Surface Hardness (Gmax) Measured via ASTM Standard F355

Surface hardness (Gmax), Head Injury Criterion (HIC), Severity Index (SI), and pad temperature of ten synthetic turf products. 2005
Treatment21-28 July11-22 August
Gmax1HIC2SI3Pad temp (°F)4Gmax1HIC2SI3Pad temp (°F)
No Wear
Astroplay78.1185.6214.679.480.9200.0231.274.0
Astroturf133.0324.5379.985.8131.4323.7388.683.1
Experimental87.5239.2292.381.490.3219.8255.581.6
Fieldturf108.2274.5334.287.5107.0259.4301.977.7
Geoturf108.0268.2312.988.8111.5285.9334.287.5
Nexturf67.9154.0180.177.473.3175.7207.780.9
Omingrass 4193.9234.3272.681.996.4257.3397.683.5
Omnigrass 5184.0212.4247.281.183.3217.7251.083.2
Sofsport90.2220.9256.983.796.6243.9283.678.1
Sprintturf108.5248.5293.582.4115.2282.2330.976.7
Wear5
Astroplay88.1219.0260.481.885.3218.6250.873.4
Astroturf138.3394.2250.388.1125.7290.6349.482.5
Experimental113.6313.9393.880.398.1246.3286.281.5
Fieldturf112.0280.5326.689.8112.4276.1321.677.4
Geoturf113.3289.6338.187.3112.6290.5338.488.9
Nexturf71.2165.1193.977.478.5195.3231.281.7
Omingrass 41109.6298.2347.382.1106.1294.4340.684.6
Omnigrass 5191.6250.1293.081.296.3273.0315.083.2
Sofsport97.4249.9290.483.597.4252.3292.877.5
Sprintturf129.1308.6308.683.4127.5323.4380.677.6
LSD (p=0.05)14.388.8130.57.611.352.461.09.3

1Surface hardness was measured according to ASTM standard F355
2HIC = Head Injury Criterion
3SI = Severity Index
4Pad temperature was measured 0.5 inch below the pile backing
5F355 testing performed after wear simulating 96 games. Grooming of plots occured on 5 and 9 Aug 2005.

Surface hardness (Gmax) of six synthetic turf products determined by ASTM standard F355 prior to and after grooming. 2006
TreatmentGmax1
11 Jul18 Aug29 Sep25 Sep2
No Wear
Astroturf127.6-126.7-
Fieldturf100.5-113.7-
Omnigrass 4190.9-93.7-
Omnigrass 5179.8-108.1-
Sofsport92.9-99.6-
Sprintturf114.6-132.7
Wear3
Astroturf130.3145.0125.7147.1
Fieldturf110.4123.0112.4127.9
Omnigrass 41103.8115.8106.1120.8
Omnigrass 5191.2101.796.3107.5
Sofsport98.4107.897.4108.7
Sprintturf128.7135.8127.5139.8
LSD3.516.311.313.3

1Surface hardness measured according to ASTM standard F355
2Data collected in plot areas with extreme wear (in tractor tire tracks).
3F355 testing performed after wear simulating 108 games. Grooming of plots occured on 223-24 Aug 2006.

Authors

Turfgrass Soil Physical Properties Playing surface characterization and safety Athletic Field and Golf Course Drainage Athletic Field and Golf Course Construction and Maintenance