Effects of an isometric conditioning activity on sprint swimming performance in high-level swimmers

This study examined whether a brief, catch-phase-resembling isometric conditioning activity (CA) combined with an individualised rest time (IRT) enhances dry-land performance and transfers to sprint swimming performance in swimmers. Twelve competitive swimmers performed a randomised, counterbalanced crossover design including two dry-land sessions and two in-water sessions. The CA consisted of maximal voluntary isometric contractions (MVIC, 3 × 3 s, 1 min rest) performed in a position resembling the front crawl catch phase. IRT was determined based on post-CA changes in MVIC measured at 4 and 8 min after the CA. Swimming kinematic and kinetic variables were assessed during a 25 m front crawl swim. The CA elicited a significant increase in the dominant arm MVIC following the IRT, whereas no significant changes were observed in the non-dominant arm. Despite this localised potentiation, no significant differences were found between experimental (with CA) and control conditions (without CA) for swimming velocity, time, force, power, stroke length, or stroke rate. A brief, catch-phase-resembling isometric dry-land CA combined with IRT enhanced dominant-arm MVIC, but did not improve sprint swimming performance. These findings suggest that isolated isometric potentiation may be insufficient to enhance performance in complex, highly coordinated tasks such as sprint swimming.