Differential Associations of the Dynamic Strength Index with Dynamic and Isometric Force Manifestations in Professional Female Soccer Players

Background/Objectives: The Dynamic Strength Index (DSI) has been proposed as an indicator of the ability to dynamically express maximum available strength; however, its practical significance remains unclear. This study examined the associations of the DSI with dynamic and isometric strength measures, as well as sprint performance, in female professional soccer players. Methods: Eighteen female professional soccer players were assessed during pre-season. The DSI was calculated from peak force obtained in the countermovement jump (CMJ) and the isometric mid-thigh pull (IMTP). Spearman’s correlations were analysed alongside bootstrap confidence intervals, false discovery rate (FDR) adjustment, dependent correlation comparisons, and partial correlations controlling for body mass. Results: The DSI showed moderate unadjusted associations with relative CMJ peak force (ρ = 0.59) and relative CMJ peak yank (ρ = 0.56). However, no associations remained statistically significant after FDR correction. Despite this, the overall pattern of effect sizes and confidence intervals suggested a tendency towards stronger associations with dynamic rather than isometric variables. No meaningful associations were observed with IMTP-derived variables or sprint performance. Conclusions: In this exploratory sample, the DSI showed a tendency towards stronger associations with relative dynamic force variables than with isometric measures. However, given the lack of statistical significance after correction for multiple comparisons, these findings should be interpreted cautiously. The DSI may be better considered as a complementary metric within a broader neuromuscular assessment framework rather than as a standalone indicator.