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playing surfaces approximately six years ago brought with it a controversy regarding the effects of these ersatz turfs on player injury rates. Following an initial manufacturer's claim alleging injury reduction on its artificial turf as compared with grassy these synthetic playing surfaces have been either maligned or r staunchly supported by coaches, players and fans. Astro Turf, Tartan Turf, Poly Turf and natural grass football fields were studied to determine the effects of these surfaces on ( 1 ) player speed, (2) impact energy absorption, and (3) shoe traction. We believe this to be the first comparative study to evaluate these parameters on a variety of playing surfaces. MATERIAL AND METHODSAstro Turf&dquo;' (Monsanto) is a synthetic turf made of 1/2 inch nylon ribbon pile of 500 denier (blade thickness) on a polyester nylon mat which is double bonded to a 5/s inch closed cell nitrile rubber and polyvinyl-chlo-ride pad on an asphalt base (Figure 1). Tartan Turf&dquo;' (3M Company) is fabricated of 1/2 inch cut nylon pile of 40-60 denier on a knitted polyester backing which is double bonded to an open cell 5/s inch polyurethane pad over an asphalt base. Poly Turf&dquo;) (U.S. Bilt-Rite) is a }í6 inch polypropylene pile of 450 denier fibers matted on a polypropylene mat and single bonded to 1/2 inch closed cell nitrile rubber and polyvinylchloride pad over an asphalt base. The grass tested was a recently mowed, one year old sodded high-school football field. Timed sprintsSix randomly selected college football players were timed in a series of 40 yd straight line and slalom dashes on grass and Astro Turf. The slalom course had pylons placed at 10, 15, 25 and 30 yd positions. Each player ran each dash 3 times on both grass and Astro Turf and average times were determined (Fig. 2). On Astro Turf an average decrease of .206 seconds per player was noted on the straight sprint and a decrease of .241 seconds per man was recorded on the slalom course as compared with grass. The slower players, who were also the heavier ones, gained the greatest proportion of speed on the synthetic surfaces. Energy absorptionSince football is a collision sport, both between players as well as between combat-From the

There is general agreement that motion between the tibia and fibula is an important and necessary part of normal ankle function in man.We studied the function of the tibiofibular unit in healthy college athletes running barefooted. Movies and cine-roentgenograms showed the fibula moving downward and laterally during the strike phase of gait. Fibular motion in this direction rather than upward, as suggested by cadaver studies, deepens the ankle mortice and stabilizes the joint when the ankle is dorsiilexed and load is the greatest. This motion also stretches the interosseous membrane and tibiofibular ligaments, converting compressive force in the ankle to tension in these structures.

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