Individually timed upper-limb post-activation performance enhancement improves 50 m front crawl performance in national-level swimmers.

Post-activation performance enhancement (PAPE) has been proposed as an acute strategy to improve sprint performance, yet evidence in swimming remains inconsistent, particularly for upper-limb protocols and segment-specific race outcomes. This study examined the acute effects of an individually timed upper-limb PAPE procedure on 50 m front crawl performance and selected race-kinematic variables in national-level male swimmers. Fifteen swimmers completed a randomized repeated-measures cross-over design comprising a control condition (CON) and an upper-limb PAPE condition. The PAPE procedure consisted of 3 sets of 6 repetitions of a prone butterfly-style double-arm pull exercise at 70% 1RM on a Keiser Functional Trainer, followed by a maximal 50 m front crawl trial performed after each swimmer's individually determined recovery time. The primary outcome was 50 m race time (T50), while start-, split-, turn-, and lap-specific stroke variables were analyzed as secondary exploratory outcomes. Compared with CON, the PAPE condition resulted in significantly faster T50 (25.44 ± 0.80 vs. 25.70 ± 0.78 s; Δ = -0.260 s, - 1.01%; p < 0.001) and T50 excluding reaction time (p < 0.001). Significant improvements were also observed for T15, T20, dive distance, flight time, turn time, and second-length stroke rate, whereas lap-specific swimming velocity, stroke length, and stroke index remained unchanged. These findings suggest that an individually timed upper-limb PAPE procedure may improve 50 m front crawl performance in national-level male swimmers, with effects expressed mainly through selected race segments rather than a uniform enhancement of free-swimming efficiency.