The effect of environmental temperature on the properties of running shoes

The purpose of this study was to investigate the effects of environmental temperature conditions and running duration on the mechanical property changes of shoes having ethylene vinyl acetate (EVA) midsoles. Midsole temperature changes were obtained for a series of 40-min runs (2 subjects, 7 runs) under various seasonal environmental temperature conditions (winter 5-15 degrees C, summer 45-55 degrees C) for a normal shoe (35 durometers, Shore A). Midsole temperatures increased an average of 8 degrees C during the initial 15-20 min of running and were followed by relatively constant temperatures. Subsequently, the mechanical properties of soft (25 durometers), moderate (35 durometers), and firm (41 durometers) midsole shoes were evaluated using an impact tester over similar temperature ranges. With increasing temperature, peak deceleration and energy absorption decreased, and the times to peak deceleration and peak deformation increased. The results suggest that ordinary running shoes with moderate midsole hardness probably provide inadequate cushioning in cold environments and inadequate rearfoot control in hot environments.