The Effect of Environmental Temperature on the Shock Absorption Capacity of Running Shoes

Abstract

0092 Various shock absorption systems (SAS) are used in contemporary running shoes to decrease lower extremity overuse injuries in runners. SAS typically include different polymeric materials with temperature sensitive biomechanical properties that may ultimately affect performance. PURPOSE: To determine the effect of temperature changes on the shock absorption capacity of four running shoes constructed with four different SAS. METHODS: Four brands of running shoes representing the most common SAS were chosen: Nike Air Triax (air-fllled units), Asics Gel Cumulus IV (gel-fllled units), Adidas Supernova (ethylene vinyl acetate or EVA), and Adidas A3 (polyurethane foam). One pair of each brand was tested (total of 4 pairs or 8 shoes). The shoes were frozen to −20° C using dry ice and gradually heated to +50° C in a portable incubator. Shoes were tested by an impactor following ASTM Standard F1614-99 at the following temperatures: −20°, −10°, 0°, +10°, +20°, +30°, +40°, +50° Celsius. The impact tester is a free-fall type impactor with instrumented force and position transducers. Output signals from both the force and position transducers were low-pass filtered at 500 Hz and sampled at 1500 Hz. From each data trial, the peak deceleration (G) was determined as an estimate of the shock absorption capacity. To assess the differences between the shoes, a repeated measures analysis of variance was used, the independent variables being the SAS and the temperature. RESULTS: There was a quadratic trend in the curves that differed between the shoe types (p< .001), indicating that for each SAS, the drop of the peak deceleration (G) with the increase of temperature was significant. There was also a significant overall difference when comparing the four different SAS over the temperature range. The polyurethane foam had much higher peak deceleration at cold temperatures than any of the other shoes tested. CONCLUSION: As the ambient temperature gets colder, the shock absorption capacity of the running shoes in the current study decreased. Temperature induced changes were most marked for the polyurethane foam SAS. These findings may have important clinical implications for individuals training in cold environments.