Effect of fatigue on force production and force application technique during repeated sprints

Abstract We investigated the changes in the technical ability of force application/orientation against the ground vs. the physical capability of total force production after a multiple-set repeated sprints series. Twelve male physical education students familiar with sprint running performed four sets of five 6-s sprints (24 s of passive rest between sprints, 3 min between sets). Sprints were performed from a standing start on an instrumented treadmill, allowing the computation of vertical ( FV ), net horizontal ( FH ) and total ( FTot ) ground reaction forces for each step. Furthermore, the ratio of forces was calculated as RF = FH FTot−1 , and the index of force application technique ( DRF ) representing the decrement in RF with increase in speed was computed as the slope of the linear RF -speed relationship. Changes between pre- (first two sprints) and post-fatigue (last two sprints) were tested using paired t -tests. Performance decreased significantly (e.g. top speed decreased by 15.7±5.4%; P