Why Swimmers Go Faster: Discriminating Swimming Velocity Using Propulsive Force and Arms Coordination

Morais, JE and Barbosa, TM. Why swimmers go faster: Discriminating swimming velocity using propulsive force and arms coordination. J Strength Cond Res XX(X): 000-000, 2026-The aim of this study was to determine whether propulsive force (PF) was associated with changes in the index of coordination (IdC) and whether both metrics were associated with swimming velocity in the front crawl stroke. The sample comprised 12 swimmers (9 males and 3 females) with an average age of 17.5 ± 1.2 years. Two swimming paces were considered: 200- and 50-m (all-out) paces. A univariate general linear model was used to examine the effect of the independent variables on the dependent variables, and effect sizes (Cohen's d and eta square-η2) were also calculated. Swimming velocity (p < 0.001, d = 2.02) and PF (p < 0.001, d = 1.71) increased between 200- and 50-m pace. The IdC changed between paces (p < 0.001, d = 3.16), shifting from a catch-up to superposition mode. The IdC model retained the PF as a predictor (p = 0.026, η2 = 0.21). The swimming velocity model retained the PF (p = 0.004, η2 = 0.35) and IdC (p = 0.050, η2 = 0.18) as predictors. Altogether, these findings indicate that greater PF and a superposition IdC were responsible for the fastest velocities. Coaches and researchers should be aware that increasing PF will promote a change in the swimmers' IdC (less time between propulsive phases), ultimately allowing swimmers to achieve the fastest velocities.