Acute kinematic changes following low-intensity tethered swimming as a constraints-led priming strategy in competitive swimmers

Background Traditional pre-activation protocols, such as post-activation performance enhancement, often rely on high-intensity stimuli, which may induce peripheral fatigue and impair fine motor control. This may be particularly problematic in swimming, where technical precision is critical. Therefore, this study examined the acute effects of low-intensity technical tethered swimming (LITTS) as a constraints-led pre-activation strategy. Methods Thirty-two adolescent competitive swimmers (mean age 13.2 ± 0.6 years) completed two pre-activation conditions on separate testing days: LITTS and a non-tethered swimming condition. Approximately 90 s following the intervention (for equipment setup), participants performed a maximal 50-m front-crawl trial. Acute technical changes were assessed using triaxial accelerometry-derived kinematic variables. Statistical comparisons were performed between conditions and pre-post responses. Results Following LITTS, significant post-intervention changes in swimming kinematics were observed. In particular, stroke length significantly improved following LITTS (F(1,29) = 47.09, p = 0.001, η 2 = 0.61). In addition, 50-m performance time was significantly shorter following LITTS compared with the free-swimming condition (F(1,29) = 9.71, p = 0.005, η 2 = 0.24). Conclusions LITTS may be an effective low-fatigue proprioceptive priming strategy in adolescent swimmers. The findings suggest that this approach may acutely improve selected swimming kinematics and short-distance swimming performance, offering a technically oriented alternative to traditional high-intensity priming protocols. Trial registration ClinicalTrials.gov, NCT07554248. Registered 17.04.2026 (retrospectively registered). https://clinicaltrials.gov/study/NCT07554248