MICROCLIMATE TEMPERATURES OF

TARTAN-TURF AND COMMON BERMUDA TURFGRASS

The development and use of synthetic turf has generated a great deal of discussion concerning its heat retention characteristics. Users of syn­thetic turf have complained that its surface and the air above its surface are warmer than the sur­face and the air above common Bermuda turf­grass.

Exercise physiologists agree that environmental temperature is an extremely important factor to consider when extensive exertion is involved. Ex­cess heat has been shown to speed dehydration,• increase the heart's rale,9 and lead to heat cramps due lo the loss of salt in perspiration5-all of which are related lo the major types of "heat injury."J

Even if an individual takes care lo avoid heal injury, his performance may be adversely affected by excess heat. Yaglou 11 found that in tempera­tures above 75° F. work output falls steadily; fur­thermore, the output of work at a comfort index [a reading based on relative humidity as well as temperature) of 93° F. was only one-half that of 70° F. Murphy and Ashe8 recommend the post­ponement of athletic practice whenever the wet­bulb temperature index reaches 76° F.

If heal accumulation and retention are signifi­cantly greater with synthetic turf than with turf­grass, then a detrimental effect on performances can logically be expected.

The amount of available research evidence re­garding the heat factor associated with synthetic turf is disproportionately small relative to the interest which exists concerning the microclimate over synthetic turf. Buskirk's2 study on Astro-Turf indicates that body heal stress on hot days is

12

Walter W. Kandelin

higher on artificial turf than on natural turf. Cooler~ reported that additional heal is gained by the player on arli ficial l urf from radiation and in­crease in air temperature. The implications of the few available studies indicate that there is a rela­tively greater heat gain on synthetic turf which could lead to greater physiological heal strain. Thus guidelines for conditioning, practice, and competition on synthetic turf in order to avoid heat injury may have lo take into account the po­tential for added heal stress.2 Coaches conducting summer and early fall practice sessions on arti­ficial turf should relax their routine and moderate demands on their athletes in initial sessions.

A study conducted at the University of Hawaii demon st rated that synthetic turf often heats lo much higher temperatures than natural grass.0

Cooke Field, one of the University's athletic fields surfaced with Tartan-Turf and surrounded by an eight-lane 440-yard Tartan track. served as one data collection location. A natural turfgrass field adjacent lo Cooke Field served as a second data collection site, This plot was fertilized and watered regularly for three weeks prior to the inauguration of testing and the plot was adjudged by a turfgrass specialist to be representative of most athletic fields, but not construed to represent the utmost in modern turf grass facilities.

One data collection station was established on each surface. Temperature measurements repre­sent twenty-one days in late September and early October of 1972. Only readings collected between the hours of 11:00 a.m. and 3:00 p.m. were used in the study.

Two Tel-Tru dial thermometers and twelve dry bulb thermometers were calibrated and used in the collection of temperature data. The thermo­meters were arranged al each station in order to collect heat measurements from four levels: sub­surface, open surface, 3 feel (air). and 5 feet [air).

Air temperature data were obtained from ther­mometers protected from the sun by aluminum foil covered shelters suspended on wood supports located al each station. Surface temperature data were obtained by placing a conventional dry bulb thermometer on the open surface at each station. Tel-Tru probe thermometers were placed in the imp act cushion under the Tartan-Turf and in the lop soil beneath the turfgrass surface.

Temperature data, recorded in degrees centi­grade, were collected at one-half hour intervals starting at 11:00 a.m. daily. The temperature read­ings were converted lo degrees Fahrenheit in re­spect to popular usage. An anemometer was used lo determine wind velocity and a solar actinome­ter was used lo measure solar radiation.

On the field surfaced with synthetic Tartan­Turf. September 27, 1972 at 1:00 p.m., tempera­tures peaked al 132.8° F. At the same lime the air temperature was 89.6° F. and the grass tempera­ture was 93.2° F.; the weather al lhe lime was clear with the relative humidity at 69%. On Oc­tober 7 al 1:30 p.m. on the Tartan-Turf field, the highest temperature of the study was recorded at 138.2° F. Air temperature was 95° F., the grass, 111.2° F.; the weather was partly cloudy with the relative humidity at 55%.

The turf grass microclimate was consistently cooler than that of Tartan-Turf. The mean three­foul air temperatures of turfgrass were cooler than those of Tartan-Turf, not only when using the daily high temperatures, but also at each of the lime periods from 11:00 a.m. until 3:00 p.m.

Air temperature, however, is not the only vari­able uf importance when considering the effects uf microclimate on human performance. Several additional indices, both of which use relative hu­midity readings in addition lo temperature, help lo serve as guides for safety in the conduct of out­door activities. These two indices are (A] the wet­bulb temperature and (Bl the Discomfort Index.

Wet-bulb temperatures were calculated for each surface and are depicted in Figure 1. It is of inter­est to note that eight of the nine Tartan-Turf mean wet-bulb temperatures were either equal to or ex-

ceeded the level at which Murphy and Ashe" rec­ommend the postponement of athletic practice. None of the turfgrass mean wet-bulb tempera­tures either equaled or exceeded this critical level.

The Discomfort Index is useful in that it is di­rectly related lo the degree of discomfort people experience from heat and humidity. The Discom­fort Indices for each surface are depicted in Figure 2. The results reflected no significant difference between the indices of the two respective sur­faces. Of interest, however, is the fact that all but one of the mean indices exceeded the level above which everyone, according to the United States Weather Bureau, 111 would be looking for relief.

In addition to the discussion of the results above, the following points were also highlighted:

1. The maximum air temperatures and surface temperatures were usually attained during the early afternoon and were influenced to a large extent by the prevailing sky conditions. The maxi­mum microclimate tempera I ure, recorded be­tween 2:00 p.m. and 2:30 p.m., reached 138.2° F. on Tartan-Turf (open surface); the highest micro­climate reading on turf grass was 113°F. The maxi­mum reading fell far short of the highest reading from a mainland investigation which recorded a high temperature of 160° F. on Astro-Turf.7 The 3M Company, manufacturers of Tartan-Turf, at­tributes this difference to Tartan-Turf's somewhat lighter green color and a higher thermal conduc­ti vily of the impact cushion.12

2. During the early morning hours of a clear day the Tartan-Turf temperature was about the same as grass tempera I ure, however, the Tartan-Turf temperature rose rapidly after sunny periods. On warm days when the atmosphere was hazy, the synthetic turf temperatures were slightly lower than the maximum. Also, after a night shower the Tartan-Turf temperatures reached maximum at a slower rate while turfgrass temperatures would remain constant for the greater part of the daily testing period.

3. The data collection period was generally characterized by fair weather, however, one ob­servation may be made from the inclement days. Rain tended to equalize microclimale tempera-1 ures on the respective surfaces.

4. A number of high readings were recorded during partly cloudy days. Coaches, therefore, should not assume that cloud cover automatically eliminates the need for precaution against heat injury.

13

5. Microclimate readings were also obtained from stations situated over the red and white por­tions of the synthetically surfaced facility. The microclimate temperatures from these two sur­faces fell between those from Tnrtan-Turf and those from the turfgrass. The red Tartan micro­climate temperature readings tended to be warm­er than those from white Tartan.

The heat retention characteristics of the Tartan­Turf field do not condemn it as an athletic surface; it has loo many obvious advantages. The coach must realize, however, that his athletes practicing and performing on synthetic turf may undergo a higher heat stress on hot days than if they were operating on natural grass. By compensating with light initial practice sessions and allowing players time fur gradual acclimatization, the possibility of heat strain may be avoided.

Bibliography

J. lJuskirk, E.R. and D. Bass. "Climate ilnd Exercise,'' Chnp­ter 17. Sdcncc: and Mnclicinu and Medi<'inc• of Ex1•rc:is,• nncl Sports. New Yurk, Harper and Bros., 1950.

2. Buskirk, E.R .. ER. McLaughlin and l,L. Loomis, Mu:ro­dimotc• Uv,:r 1\rtifii 101 Turf, JOHPER. (Novl!lnlmr Der.emher. 19711,

J . Buskirk. E.R. and W.C. Grnsley. "Heat Injury nnd Con­duct of Athletics," Pror.crdings of Conf1:rnnw nn 111•111 Injury <11111 1\th/clics, Chii:ago, Athletic lnslilulc, 1968, pp. 49•51.

4. Cooler, Ranklin G. "Heal Control in Athlelir.s," Sc:/mlosti1: Cuoc/1, Vol. 42, No. 2, (October, 1972).

5. Lind, A.R. "Physiologic Effects of Conlinunus or lnter­miltenl Work in the Heat,'' /ournu/ of ,\pp/kd Physiology, (19631, lll(l):57.

6. Knndelin. Walter W. "A Comparison of Microclimnle Tem­peratures nf Tartan•Turf and Common Bermuda Tur£grass." Unpublished M.A. Pinn "B'' Paper, Universil y or l·lnwaii, 1973.

7. Macklcnburii, Roy. "Arti£icinl Turf is Hot Stuff.'' Mid11g1111 Nurseryman 's ,\ssocintron Mni,:nzrnc, December, 1971.

II. Murphy. R.f. and W.F. Ashe. "Prevention of Hunt Illness in Football Players,'' /1\MJ\. (Nov. 8, 1965), 194:189.

!J. Toor, M. ct. al. "Eler.trncardiographic Changes During Daily Work and Acute Exercise m Permanent Inhabitants nf Hot Areas," J\mcricon Huorl Journal. February, 1965. p. 181.

10. United States Weather Bureau. Tec:hnir.al Bulletin No. 11. 1!155, WashinRlon, D.C., U.S. Government Prinlin!l Offir.e.

11. Yaglou. C. Jl. and D. Minard. "Control of Heal Casualties al Militnry Trnining Centers," Arrh. Indus!. Henlth. 1957, 16:302-316.

12. Letter from 3M, Minnesota Mining and Manufnr.turing Company, Saini Paul, Minnesota, May 1, 1973.

14

Wn/lcr "undc/in is Pl1ysir.u/ Education lnstrut:tor one/ Dircl'lor of J\thlc11cs at Univcrsit,y Laboratory High School. n rnpocify /w hns s11rvcd in since 1!169. He rcr.dvt:d his M.Ecl. cfogrcm from tlw U111vcrs1ly of /fo1vaii, Manou in 1972. Mr. Kunde/in is a rclirnd U.S. t\rmy Major.