P. Krol, E. Redfern, M. Gruler, E. Erwert, D. Dorta, J. Lo, D. Guinasso, R.McCulloch 1

1Gonzaga University, Spokane, WA

Athletes seek advantages over competitors, especially at movement initiation, when athletes tend to have the largest change in velocity. A false step (FS), defined as a backwards step before moving in the intended direction, is a debated starting technique for athletes. Prior research has focused on kinematic factors for straight sprints, however, most sports movement is multiplanar. PURPOSE: This study examined biomechanical changes of an athlete when performing a FS to initiate a forward sprint, from both parallel and lateral starts, and a jump. METHODS: Athletes (N=34, 21.0 ± 0.8 yr) had electromyography (EMG) for the quadricep, hamstring, gluteus medius and gastrocnemius for both legs, and ground reaction forces in the ant/post and vertical direction recorded. Three types of trials performed: straight run with parallel start (feet shoulder width apart), straight run with lateral start (facing perpendicular to run direction), and vertical jump. Three FS and 3 non-false step (NFS) trials were performed for each direction. The foot hitting the force plate (Strike foot: S) remained consistent and the foot performing the false step (non-strike foot: NS) remained consistent. Paired t-tests were used for EMG (% MVIC), maximum force, and impulse. p< .05 was significant, and p<.1 was a trend towards significance. RESULTS: Straight run: NS quadricep activation was significantly larger for FS trials (mean difference (MD)=5.75 % p<.001) and impulse for FS (MD=5.71 Ns, p=.004). Lateral: Higher S quadricep activation during FS trials (MD=5.1 %, p=.003), with a trend for the impulse (MD= 2.3 Ns, p=.089). Jump: S hamstring (p=.004) NS hamstring (p=.058) created more activation during the FS trials, and there was a larger maximum force for the FS (p=.026) and significantly larger impulse for NFS (p=.027). CONCLUSION: Larger quadricep activation for lateral and straight trials was attributed to the propulsion while performing the FS. Recruitment of this large muscle group resulted in a powerful push off phase in the first few steps of performing FS, as evidenced by higher horizontal impulses. There were no notable differences in jump performance with a FS. Our results suggest implementing the FS into an athlete’s repertoire when initiating explosive running movements from a straight or lateral start, to benefit overall performance.

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