Acute effects of light weighted vests on sprint velocity, step frequency, and step length in female basketball players

Abstract

Sprint acceleration is a critical performance factor in basketball, and weighted vests (WVs) offer a practical means of resisted sprint training. However, limited female-specific evidence exists on the acute effects of light wearable loads on acceleration-phase sprint velocity and its kinematic determinants. This study examined the acute effects of light WVs on sprint velocity and step kinematics in female basketball players, with an emphasis on individual adjustment strategies. Twelve collegiate athletes completed two 20-m linear sprints under three randomized conditions: no load (0%), WV at 3% body mass, and WV at 5% body mass. Sprint performance was assessed using timing gates, and a side-on high-speed camera (240 fps) recorded the 5–15 m interval to quantify step frequency (SF), step length (SL), ground contact time (GCT), and flight time over one gait cycle. Sprint velocity was computed as SF × SL. Group comparisons using one-way ANOVA revealed a significant main effect only for sprint velocity (F(2,22) = 3.78, p < 0.05, ω² = 0.13), with velocity at 5% significantly lower than at 0% (p < 0.05). By contrast, SF, SL, GCT, and flight time did not differ significantly across conditions at the group level. However, within-subject percent-change analyses provided clearer mechanistic insight. At 5% load, the percent change in SF was strongly and positively associated with the percent change in sprint velocity (r = 0.871, p < 0.001), whereas percent changes in SF and SL were negatively related (r = −0.725, p < 0.01), indicating a systematic SF–SL tradeoff under load. Athletes who best preserved sprint velocity at 5% tended to maintain cadence (SF) while accepting modest reductions in SL; conversely, larger velocity decrements coincided with reduced SF despite relatively maintained SL. The unloaded pitch–stride ratio (PS ratio = SF/SL) showed a moderate correlation with the direction of SL adjustment at 5% (r = 0.583, p < 0.05), suggesting that baseline running style may relate to how athletes redistribute SF and SL when loaded, although this relationship does not support predictive use. Practically, initiating WV exposure at approximately 3% body mass while prioritizing cadence preservation and monitoring velocity decrement may be advisable for female basketball players. Overall, under light loading, sprint-velocity maintenance appears to hinge on protecting SF, highlighting the need for individualized WV prescription and monitoring.