Hunter L. Frisk1, Alicia L. Thone1, Randall L. Jensen FACSM2, and William P. Ebben1

Lakeland University, Plymouth WI; Northern Michigan University, Marquette, MI

A variety of biomechanical factors, experience level, and training specificity may influence sprinting acceleration. PURPOSE: This study evaluated kinetic and kinematic variables during the early acceleration phase of sprinting with an acceleration ladder. METHODS: Ten women (age = 19.3 ± 1.06 years) and ten men (age = 20.01 ± 0.99 years) served as subjects and provided written consent. The study was approved by the Institutional Review Board. Subjects performed 10-meter sprints in sprinter (SP) and standing (ST) start conditions, across two flush-mounted force platforms in series, using an acceleration ladder. Subject’s horizontal ground reaction force (H-GRF), vertical ground reaction force (V-GRF), H-GRF to V-GRF ratio (H:V), time between steps, stride frequency, and speed were assessed. Pearson’s correlation coefficients were used to determine the relationship between sprinting velocity during each start condition and H-GRF, V-GRF, H:V, time between steps, average stride frequency (SF), duration of foot contact, and stride distance, between steps and across all four steps. RESULTS: For the SP start condition, significant (p ≤ 0.05) correlations were found between the overall velocity of the four steps and H-GRF (r = -0.46), V-GRF (r = -0.71), H:V (r = 0.46), and step distances between the third to fourth step (r = 0.65). For the ST start condition, significant (p ≤ 0.05) correlations were found between the overall velocity of the four steps and V-GRF (r = -0.51), SF (r = -0.92), and foot contact duration (r = -0.56). No other significant correlations (p ≥ 0.05) were found. CONCLUSION: Training the optimal ratio of H-GRF to V-GRF seems to be more important than the magnitude of force in either plane, since H-GRF and V-GRF were not positively correlated with sprint velocity, but H:V was for the sprint start. While longer foot contact time theoretically would facilitate greater force production, predictably the duration of foot contact was negatively correlated with velocity. Additionally, high stride frequency and step distances that are too short impair velocity. Athletes should be trained to develop brief foot contact time and use sufficient step distance when sprinting with acceleration ladders. Acceleration ladders configured with rung spacing that is too close likely inhibits optimal sprinting velocity.

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