Changes in gait during constant pace treadmill running.

Treadmills are often used by runners when weather conditions are adverse or a specific training effect is desired. Athletes might respond to fatigue differently when running on a treadmill compared with overground conditions, where pace is typically more variable. The purpose of this study was to measure changes in gait parameters over the course of a 10-km treadmill run. Fifteen male competitive runners ran at a constant pace for 10 km at 103% of season's best time on an instrumented treadmill with in-dwelling force plates, and data were analyzed at 5 distances. Kinematic data were derived from high-speed videography and results compared between the early and late stages. Before halfway, step length increased and cadence decreased, whereas during the latter stages, there were significant decreases in impulse and maximum force. Contact time decreased and flight time increased continually, but otherwise most gait variables did not change. The changes in contact and flight times suggested that athletes altered their gait so that more time was spent airborne to allow the treadmill to pass under them. In general, however, the runners maintained their techniques throughout the run. Constant pace treadmill running might therefore be useful with the aim of running for a particular distance and speed with a consistent technique unaffected by factors such as gradient or fatigue. However, the increase in flight time might have aided the runners because of the nature of treadmill running, and athletes and coaches should note that this training effect is impractical during overground running.