Development of Dynamic Strength Index Based on Free-Weight Exercises for Collegiate Male Sprinters

Chino, K, Tokuoka, H, and Ito, Y. Development of dynamic strength index based on free-weight exercises for collegiate male sprinters. J Strength Cond Res 39(5): e639-e646, 2025-The dynamic strength index (DSI) serves as a predictive measure of dynamic performance qualities, calculated as the ratio of peak force during the countermovement jump (CMJ-PF) to that during the isometric midthigh pull (IMTP-PF). This study aimed to develop a method for determining the DSI using free weights instead of a force plate for collegiate male sprinters. Thirteen collegiate male sprinters (age, 20.0 ± 0.8 years) underwent measurements of CMJ-PF and IMTP-PF using a force plate. In addition, 1 repetition maximum (1RM) of the back squat, deadlift (DL), and trap-bar deadlift was measured as alternative indicators of IMTP-PF. As alternative indicators of CMJ-PF, the 1RM of the hang clean, barbell squat jump (SJ-1RM), and trap-bar squat jump was measured. Among the alternative IMTP-PF indicators, DL-1RM exhibited the strongest correlation with IMTP-PF (r = 0.52). Among the alternative CMJ-PF indicators, SJ-1RM showed the strongest correlation with CMJ-PF (r = 0.69). Furthermore, the alternative DSI calculated as the ratio of SJ-1RM to DL-1RM demonstrated the strongest correlation with the DSI (r = 0.56) among the alternative DSIs. Corresponding to a "very high" DSI (>0.80) and a "low" DSI (<0.60), the alternative DSI values calculated as the SJ-1RM to DL-1RM ratio were 0.30 and 0.43, respectively. Using the alternative DSI, derived from the SJ-1RM to DL-1RM ratio, coaches and practitioners can assess the dynamic performance qualities of collegiate male sprinters using free weights instead of a force plate.