Relative Strength, Rate of Force Development, and Body Mass Ratios Correlate to Dynamic Sports Performance in Youth Athletes

Recreational youth athletes (n = 50) ages (14.58 years ± 3.1) were assessed to evaluate relationships between isometric strength, isometric rate of force development, total body mass and dynamic sports performance assessments. Athletes performed isometric mid-thigh pull, counter-movement jump, drop jump, 20 meter sprint with a 10m split gate as well as the 5-10-5 agility shuttle. Relative Strength Ratios (RSR), Relative Rate of Force Development ratios (RRFD) and isometric rate of force to Max Force Ratios (RFM) were developed and compared to each of the dynamic performance assessments. K-means clustering analysis to create 3 groups for RSR RRFD and RFM were found to correlate to dynamic sports assessments. RSR was found to show moderate correlations, both positive and negative, with dynamic sports assessments. The results show moderate to strong correlations, both positive and negative, with dynamic sports assessments in all but 2 assessments for RRFD. RFM results had very weak, nonsignificant results. Results of ANOVA of each of the ratios to performance outcome measures were found to be significant with small effect sizes. The primary finding of this investigation suggests youth athletes with RSRhigh (2.0+) and RRFDhigh (1.5+) with RFMlow (0.79) performed better than all other youth athletes. Utilizing RSR alone, youth athletes with RSRhigh (2.0+) performed better than all other athletes. The secondary finding of this investigation suggests that thresholds do exist for RSR, RRFD and RFM when compared to dynamic sports assessments which could be used for intake assessments and age-appropriate program design for youth athletes. Assessing youth athletes via relative strength ratios considering isometric force production and total body mass with respect to lean body mass and percent body fat may provide additional insight into training programming and body composition modifications to increase dynamic sports performance.