BACKGROUND: The swim start is a key determinant of sprint swimming performance, yet the practical value of dry-land force-platform testing for identifying start-related neuromuscular qualities remains unclear in competitive swimmers. This study examined which variables derived from the isometric mid-thigh pull (IMTP), squat jump (SJ), and countermovement jump (CMJ) were most strongly associated with early swim-start performance, expressed as mean time to 5 m. METHODS: Sixteen national-level Tier-4 swimmers from Uruguay (10 males, 6 females) performed three maximal starts in a 25-m pool using the start condition corresponding to the event in which they usually compete, together with a dry-land force-platform battery including IMTP, SJ, and CMJ. Time to 5 m was obtained from GoPro Hero7 video recordings using Kinovea software. Kinetic variables were obtained from dual Ivolution® force platforms sampling at 500 Hz. Variables derived from IMTP, SJ, and CMJ were analyzed, including modified reactive strength index (RSI_mod), defined as jump height divided by time to take-off. Paired comparisons were used to examine front-leg and rear-leg differences. An initial exploratory Bayesian correlation screening and a parsimonious within-block selection strategy were applied, followed by sex-adjusted Bayesian regression models. RESULTS: IMTP peak force was the only variable that differed significantly between front and rear legs, with higher values in the rear leg (1059 ± 263.7 N vs. 995 ± 279 N; p = 0.014; Hedges` g = 0.734). Within-block selection retained IMTP rear-leg peak force, SJ jump height, and CMJ-derived RSI_mod as representative predictors. All three variables showed negative associations with time to 5 m in the sex-adjusted univariate models, but RSI_mod showed the strongest evidence and best parsimonious fit (Bayes factor = 66.813; R² = 0.732; adjusted R² = 0.683; * = -0.089; 95% CrI: -0.161 to -0.017). Among the combined models, the model including SJ jump height and RSI_mod explained the greatest proportion of variance (R² = 0.806; adjusted R² = 0.741), but only RSI_mod retained a 95% credible interval excluding zero. CONCLUSIONS: Force-platform testing appears to provide practically useful information about early swim-start performance in national-level Tier-4 swimmers. RSI_mod emerged as the most robust single indicator of start-related explosive performance in this population
© Copyright 2026 XVth International Symposium on Biomechanics and Medicine in Swimming Proceedings. Alle Rechte vorbehalten.