Purpose: This study prospectively monitored changes in repeated-sprint swimming performance, blood lactate ([La]) concentration, and countermovement-jump (CMJ) performance during a 6-month training period with traditionally periodized endurance training in competitive swimmers. Methods: Twenty well-trained sprint and middle-distance swimmers (mean [SD]; age = 18 [2] y, body mass = 69.6 [8.0] kg, height = 179 [6.1] cm) underwent body-composition assessment and completed a 7 × 50-m repeated-sprint test, with measurements of [La] and CMJ, before (October, preparation period) and after (April, early-competition period) a 6-month training period using traditional periodization. Results: There were no significant improvements in swimming velocity, CMJ height, or changes in [La] from October to April, with considerable individual variation. However, there was a small but significant increase in fat-free mass (mean difference ± SD: 0.9 ± 2.2 kg), albeit with a small effect size, and no changes in body fat or body mass. Significant and expected decreases in performance (swimming and CMJ) across the repetitions of the 7 × 50-m repeated-sprint tests were observed, accompanied by increases in [La], all with large effect sizes, but there was no evidence that training affected these results (no significant interactions). Conclusion: A 6-month training period with traditionally periodized endurance training failed to significantly improve repeated-sprint swimming performance, [La] response, or CMJ height in trained swimmers across the 2 training phases. TO OUR READERS: An error appeared in the ahead-of-print version of the following article: Gonzalez-Rave JM, Sandbakk Ø, Lopez-Hernandez A, Rodríguez-Barbero Expósito S, Valero F, Muñoz de la Cruz V, Turner AP. Limited effects of a 6-month training period on repeated-sprint performance, blood lactate, and jump performance in competitive swimmers. Int J Sports Physiol Perform. Published online June 23, 2025. https://doi.org/10.1123/ijspp.2025-0028 The affiliation of Sergio Rodríguez-Barbero Expósito with Facultad Ciencias de la Salud y Escuela de Doctorado, Universidad Internacional de La Rioja, Logroño, Spain, was mistakenly deleted in the author proofing process. The article was corrected July 1, 2025. The authors apologize for the error.
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