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ORIGINAL RESEARCH article
Front. Physiol.
Sec. Exercise Physiology
Volume 16 - 2025 |
doi: 10.3389/fphys.2025.1551488
This article is part of the Research Topic Acute and Chronic Physiological Adaptations to Resistance Exercises Across Various Populations: Mechanisms and Practical Applications View all 3 articles
The Role of Starting Knee Angle in Squat Jump Force-Velocity Profiles: Interactions with Subjects' Strength Levels and Imputed Push-Off Distance
Provisionally accepted- 1 Nanjing Sport Institute, Nanjing University, Nanjing, Jiangsu Province, China
- 2 Affiliated Jinling Hospital, School of Medicine, Nanjing University, Nanjing, Jiangsu Province, China
- 3 University of Granada, Granada, Spain
This study investigated whether differences in the force-velocity (F-v) profile obtained using Samozino's method during squat jumps (SJ) performed at varying knee angles are influenced by subjects' strength levels and the push-off distance (HpO) used in the analysis. Twenty-one resistancetrained men were classified as stronger (n = 10) or weaker (n = 11) based on the external load required to achieve a 10 cm SJ height. F-v profiles were randomly assessed over three sessions, with SJs performed at starting knee angles of 70º (SJ70), 90º (SJ90), and 110º (SJ110), using either the actual HpO specific to each condition or a standardized HpO corresponding to SJ90. Significant differences between SJ types were observed for maximum force (F0) and the F-v slope (SJ110 > SJ90 > SJ70). These differences were never influenced by subjects' strength levels. The standardized HpO produced similar outcomes for maximum power (Pmax) and maximum velocity (v0), and more consistent results for F0 and the F-v slope compared to the actual HpO. Regardless of strength levels, standardizing HpO at 90º and allowing subjects to select a starting knee angle between 70º and 90º could simplify the evaluation process and improve the comparability of F-v profiles across subjects when using Samozino's method.
Keywords: Biomechanics, kinematics, lower-body function, testing, power
Received: 25 Dec 2024; Accepted: 22 Jan 2025.
Copyright: © 2025 Qin, Liu, Tang, Liu and García-Ramos. 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:
Xuelin Qin, Nanjing Sport Institute, Nanjing University, Nanjing, 210093, Jiangsu Province, China
Amador García-Ramos, University of Granada, Granada, Spain
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