ORIGINAL RESEARCH article
Front. Sports Act. Living
Sec. Elite Sports and Performance Enhancement
Volume 7 - 2025 | doi: 10.3389/fspor.2025.1598396
Unilateral and Bilateral load-velocity relationships in athletes: evidence from a study in boxers
Provisionally accepted
- Shanghai Sports School, Shanghai, China
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This study aimed to investigate the load-velocity (L-V) relationship in boxers during unilateral (Bulgarian split-squat, BSS) and bilateral (back-squat, BS) lowerlimb exercises, and to compare the mean velocity (MV) outputs between these two modalities, with the ultimate goal of providing an evidence-based foundation for optimizing strength training in boxing.Twenty trained boxers (age: 19.7 ± 1.0 years) performed incremental loading tests on a Smith machine equipped with a linear position transducer (GymAware) to record MV. Unilateral testing was performed on each leg in a randomized order, with loading progressed incrementally from 30% to 100% of the predicted one repetition maximum (1RM). Participants performed three repetitions at 30-70% predicted 1RM, two repetitions at 75-90% predicted 1RM, and one repetition at 95-100% predicted 1RM, with a 10-second rest between repetitions and a 5-minute rest between load conditions.We found a close relationship between MV and relative load (%1RM) in both BSS and BS exercises for the non-dominant legs (coefficient of determination; R² = 0.94, standard error of estimate; SEE = 0.05 m•s⁻¹), dominant legs (R² = 0.94, SEE = 0.05 m•s⁻¹), and back-squat (R² = 0.95, SEE = 0.05 m•s⁻¹), reflecting a nearly perfect relationship as per standard interpretations of coefficient strength. Compared to Bulgarian split-squat, back-squat exhibited significantly higher MV at the same %1RM (P < 0.01, η² = 0.256).This study validated the use of velocity-based resistance training (VBT) to optimize strength training in boxing. Both unilateral and bilateral exercises showed consistent L-V relationships, supporting individualized load prescription. Bilateral exercises enhanced velocity output, while unilateral exercises helped correct inter-limb strength asymmetries and improve sport-specific stability.
Keywords: combat sports, strength training, velocity-based resistance training, load-velocity relationship, Unilateral and bilateral exercises
Received: 23 Mar 2025; Accepted: 13 Oct 2025.
Copyright: © 2025 Han, Xie, 牛, Jia and Zhang. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence:
Yemin Han, 2321151092@sus.edu.cn
Zhen Zhang, zhangzhen@sus.edu.cn
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