Purpose: Despite the growing global prominence of elite open-water (OW) swimming, little is known about how seasonal variation influences the physiological and kinematic determinants of maximal performance. This study aimed (1) to evaluate the seasonal changes in performance, physiological, and kinematic factors in maximal incremental swimming tests in elite OW swimmers and (2) to examine the influence of physiological and kinematic factors on the maximal swimming performance. Methods: Eighteen world-class and elite (12 males [25.4 (3.3 y)] and 6 females [26.4 (3.9) y]) OW swimmers voluntarily participated. A total of 57 (40 male and 17 female) intermittent incremental tests (7 × 400 m) in a 50-m pool were analyzed at 4 different moments (October 2022, February and October 2023 and March 2024). Heart rate; blood lactate concentration ([La-]); aerobic (AeT) and lactate thresholds (LT); swimming speed; and stroke rate, length, and index were assessed. Results: The OW swimmers showed no changes in performance or physiological factors between tests. In males, the stroke length and index changed in both AeT and LT, whereas no kinematic changes were observed in females. The maximum swimming speed was positively associated with speed at AeT and LT in both sexes, while only males showed association between [La-] at LT. Stroke length and index at AeT and LT in males and stroke rate at AeT and LT were positively associated with maximum swimming speed. Conclusions: Despite stable performance and physiological factors, seasonal changes in stroke technique highlight the importance of monitoring kinematics to guide training or competition of elite swimmers.
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