The Correlation between Net Impulse and Phases of Linear Sprint Performance in University American Football Players

Impulse has been proposed as a reliable performance measure when assessing force generating capacity, during a given time frame, and in recent literature has been investigated to its degree of relationship with sprint performance. This study investigated the correlation between early epochs of net impulse from isometric actions and selected phases of linear sprint performance. A within subject design was employed to assess the correlation between linear sprint performance and epochs of net impulse in 29 university American Football athletes (mean±SD: age = 20.10±1.53 years; height = 181.69±5.63cm; weight = 95.92±22.81kg). Net impulse was measured over epochs of 0-100, 0-150, and 0-200 milliseconds (Newtons per second) via an isometric mid-thigh pull protocol while linear speed was assessed using linear sprint testing (10 and 36.58 metres). Pearson’s r correlation coefficient was used to evaluate correlations between assessed variables and effect size. The analysis demonstrated trivial to small correlations (r=-0.06 to 0.18) between early epochs of net impulse and linear sprint performance. The 10-metre linear sprint performance demonstrated small correlations at 0-150 milliseconds (r=0.18) while the remaining variables revealed trivial correlations. The effect size indicated trivial to small correlations between the assessed variables. Although no significant correlation was found between isometric mid-thigh pull metrics and linear sprint performance these findings provide meaningful insight into the complexity of sprinting mechanics, in the assessed population. If net impulse does not strongly correlate with sprint performance, it may indicate the need to reassess the emphasis placed on isometric strength assessments in sprint profiling.