The role of starting knee angle in squat jump force-velocity profiles: interactions with subjects’ strength levels and imputed push-off distance
IntroductionThis 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.MethodsTwenty-one res...
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Frontiers Media S.A.
2025-02-01
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| author | Xuelin Qin Beibei Liu Ruolin Tang Yan Liu Amador García-Ramos Amador García-Ramos |
| author_facet | Xuelin Qin Beibei Liu Ruolin Tang Yan Liu Amador García-Ramos Amador García-Ramos |
| author_sort | Xuelin Qin |
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| description | IntroductionThis 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.MethodsTwenty-one resistance-trained 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 70° (SJ70), 90° (SJ90), and 110° (SJ110), using either the actual HpO specific to each condition or a standardized HpO corresponding to SJ90.ResultsSignificant 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.DiscussionRegardless of strength levels, standardizing HpO at 90° and allowing subjects to select a starting knee angle between 70° and 90° could simplify the evaluation process and improve the comparability of F-v profiles across subjects when using Samozino’s method. |
| format | Article |
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| institution | Kabale University |
| issn | 1664-042X |
| language | English |
| publishDate | 2025-02-01 |
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| spelling | doaj-art-2fbcf118ddb34c759c6c67c87cafb3b62025-02-12T07:26:06ZengFrontiers Media S.A.Frontiers in Physiology1664-042X2025-02-011610.3389/fphys.2025.15514881551488The role of starting knee angle in squat jump force-velocity profiles: interactions with subjects’ strength levels and imputed push-off distanceXuelin Qin0Beibei Liu1Ruolin Tang2Yan Liu3Amador García-Ramos4Amador García-Ramos5Department of Sport Science, Nanjing Sport Institute, Nanjing, ChinaDepartment of Rehabilitation, Jinling Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, ChinaDepartment of Sport Science, Nanjing Sport Institute, Nanjing, ChinaDepartment of Sport Science, Nanjing Sport Institute, Nanjing, ChinaDepartment of Physical Education and Sport, Faculty of Sport Sciences, University of Granada, Granada, SpainDepartment of Sports Sciences and Physical Conditioning, Faculty of Education, Universidad Católica de la Santísima Concepción, Concepción, ChileIntroductionThis 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.MethodsTwenty-one resistance-trained 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 70° (SJ70), 90° (SJ90), and 110° (SJ110), using either the actual HpO specific to each condition or a standardized HpO corresponding to SJ90.ResultsSignificant 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.DiscussionRegardless of strength levels, standardizing HpO at 90° and allowing subjects to select a starting knee angle between 70° and 90° could simplify the evaluation process and improve the comparability of F-v profiles across subjects when using Samozino’s method.https://www.frontiersin.org/articles/10.3389/fphys.2025.1551488/fullbiomechanicskinematicslower-body functiontestingpower |
| spellingShingle | Xuelin Qin Beibei Liu Ruolin Tang Yan Liu Amador García-Ramos Amador García-Ramos The role of starting knee angle in squat jump force-velocity profiles: interactions with subjects’ strength levels and imputed push-off distance Frontiers in Physiology biomechanics kinematics lower-body function testing power |
| title | The role of starting knee angle in squat jump force-velocity profiles: interactions with subjects’ strength levels and imputed push-off distance |
| title_full | The role of starting knee angle in squat jump force-velocity profiles: interactions with subjects’ strength levels and imputed push-off distance |
| title_fullStr | The role of starting knee angle in squat jump force-velocity profiles: interactions with subjects’ strength levels and imputed push-off distance |
| title_full_unstemmed | The role of starting knee angle in squat jump force-velocity profiles: interactions with subjects’ strength levels and imputed push-off distance |
| title_short | The role of starting knee angle in squat jump force-velocity profiles: interactions with subjects’ strength levels and imputed push-off distance |
| title_sort | role of starting knee angle in squat jump force velocity profiles interactions with subjects strength levels and imputed push off distance |
| topic | biomechanics kinematics lower-body function testing power |
| url | https://www.frontiersin.org/articles/10.3389/fphys.2025.1551488/full |
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