Detraining Effect on Sprint Swimming Performance and Load–Velocity Profile Ruiz Navarro, Jesús Juan López Belmonte, Óscar Febles-Castro, Adrián Gay Párraga, Ana López Contreras, Gracia Morales Ortiz, Esther Arellano Colomina, Raúl semitethered strength training cessation testing off-season biomechanics sport physiology exercise performance This study was supported by the Grant 379 PID2022.142147NB.100 (SWIM III) funded by MICIU/AEI/10.13039/501100011033/ 380 and by ERDF, EU. AFC has an FPI fellowship, PID2022-142147NB-I00, which is part 381 of the aforementioned grant and OLB was supported by the grant FPU19/02477 funded 382 by MICIU/AEI/10.13039/501100011033. Purpose: To assess the effect of 5-week training-cessation period on performance and load–velocity profile-related variables. Methods: Twenty-four competitive swimmers (15 male and 9 female: 19.2 [3.7] and 17.3 [2.3] y, 50-m front-crawl 550 [70], and 572 [51] World Aquatics points, respectively) performed a 50-m front-crawl all-out swim, a load–velocity profile, and a pull-up test before and after a 5-week off-season period. Kinematic variables, blood lactate concentration, and rating of perceived exertion were monitored during the load–velocity profile tests. Results: Performance was impaired 1.3% for males (P < .01) and 3.8% for females (P < .01). Neither anthropometric changes (males r2 = .277, females r2 = .218, P > .05) nor the physical activity performed during the off-season (males r2 = .329, females r2 = .094, P > .05) attenuated performance impairments. While males counteracted the stroke-rate decline (P < .05) by increasing stroke length (P < .05) in the majority of the race, females did not, leading to a decline in clean swimming speed (P < .05). The maximum load at zero velocity decreased (P < .05) during the load–velocity profile test. In addition, males showed an increased blood lactate concentration (P < .05), whereas females decreased the maximum velocity at zero load (P < .01) and stroke rate (P < .01). No change in the slope was observed for either sex (P > .05). Conclusion: Following a 5-week off-season period, sprint swimming performance declines (males 0.34 s; females 1.15 s). The load–velocity profile and related variables evidenced deterioration, showing changes in blood lactate concentration, maximum load at zero velocity, average velocity during the third trial, and stroke rate. 2025-05-28T06:55:08Z 2025-05-28T06:55:08Z 2024-12-01 journal article Published version: Ruiz Navarro, Jesús Juan et al. Detraining Effect on Sprint Swimming Performance and Load–Velocity Profile. International Journal of Sports Physiology and Performance. 2025. DOI: 10.1123/ijspp.2024-0491 https://hdl.handle.net/10481/104293 10.1123/ijspp.2024-0491 eng open access Human Kinetics