Technical Stroke Regulations Discriminate Pacing Effectiveness During a 5-km Indoor Pool Race.

Purpose: To investigate technical regulation mechanisms of long-distance swimmers that differentiate optimal pacing strategies and the underlying kinematic parameters.

Methods: Twenty-one national and international swimmers were equipped with a sacrum-worn inertial measurement unit performed during 5000-m indoor French championships. Percentage of critical swimming speed (CSS), stroke rate, stroke length, jerk cost, stroke index, and mechanical proficiency score were computed by lap. Athletes were divided into groups of pacing effectiveness based on optimal potential performance level (OPPL)-optimal (nearOPPL) and suboptimal (farOPPL)-using functional clustering of percentage of the CSS. Race sections were analyzed with a change-in-slope detection method. Common stroke-regulation abilities and deviations by pacing groups were profiled by fitting hierarchical generalized additive models between mechanical variables and laps.

Results: The 2 clusters were discriminated by percentage of the CSS sustainment (P < .01). Optimal performers showed a +41.4% more stable pacing (2 race sections vs 3 for farOPPL) and a +36.7% higher end spurt, with a trend combining higher overall stroke rate (P = .08) with lower jerk cost (P = .17). Functional profiles showed that maintaining a higher stroke length and stroke index in a fatigued state, rather than overall values, allows the swinner to reach OPPL (P < .001). High regulation of mechanical proficiency score across the race, in line with pacing expectations of particular race sections, is a game changer to sustain CSS (P < .001).

Conclusions: Specific profiles of stroke regulations, regarding tradeoff between stroke smoothness and resultant speed, lead to optimal pacing during the 5000-m. The results of this study enhance the technical understanding of optimal pacing in long-distance pool races for coaches and swimmers.