Volume 12, Issue 2 (winter 2026)
IJRN 2026, 12(2): 46-54 |
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Assistant Prof. of Sport Biomechanics, Dept. of Physical education and Sport Science, Faculty of Educational Science and psychology, University of Mohaghegh Ardabili, Ardabil, Iran. barghamadi@uma.ac.ir
Abstract: (710 Views)
Introduction: Combat sports, due to the frequent use of upper and lower limb strikes, often induce fatigue, which can reduce both static and dynamic balance. Accordingly, the present study aimed to compare the effects of fatigue on the frequency spectrum of ground reaction forces during the Ap Chagi kick in healthy taekwondo practitioners and those with anterior cruciate ligament injury.
Methods: This study employed a quasi-experimental, laboratory-based design. Participants included 15 male athletes with ACL injury and 15 healthy male athletes. GRF variables were recorded using a force plate, and all force amplitudes were normalised to body weight. The Shapiro–Wilk test was applied to verify the normality of data distribution. Statistical analyses were conducted using a two-way repeated-measures ANOVA with a significance level set at p ≤ 0.050. All analyses were performed using SPSS version 26.
Results: The main effect of time on the 99.5% power frequency component in the mediolateral direction was significantly lower in the post-test than in the pre-test (p = 0.048; d = 0.175). Conversely, the main effect of time on the 99.5% power frequency component in the vertical GRF was significantly higher in the post-test compared to the pre-test (p = 0.036; d = 0.052). Moreover, the time × group interaction revealed that post-test vertical GRF values in the ACL-injured group were 35.76% higher than those in the healthy group (p = 0.045; d = 0.089).
Conclusion: The findings demonstrate that fatigue induces greater alterations in the frequency characteristics of GRFs in ACL-injured taekwondo practitioners compared to healthy athletes. This pattern reflects a decline in neuromuscular efficiency, reduced functional stability, and slower execution of motor skills. The results highlight the need for targeted training and rehabilitation interventions to improve frequency-domain parameters and enhance dynamic stability in athletes with a history of ACL injury.
Methods: This study employed a quasi-experimental, laboratory-based design. Participants included 15 male athletes with ACL injury and 15 healthy male athletes. GRF variables were recorded using a force plate, and all force amplitudes were normalised to body weight. The Shapiro–Wilk test was applied to verify the normality of data distribution. Statistical analyses were conducted using a two-way repeated-measures ANOVA with a significance level set at p ≤ 0.050. All analyses were performed using SPSS version 26.
Results: The main effect of time on the 99.5% power frequency component in the mediolateral direction was significantly lower in the post-test than in the pre-test (p = 0.048; d = 0.175). Conversely, the main effect of time on the 99.5% power frequency component in the vertical GRF was significantly higher in the post-test compared to the pre-test (p = 0.036; d = 0.052). Moreover, the time × group interaction revealed that post-test vertical GRF values in the ACL-injured group were 35.76% higher than those in the healthy group (p = 0.045; d = 0.089).
Conclusion: The findings demonstrate that fatigue induces greater alterations in the frequency characteristics of GRFs in ACL-injured taekwondo practitioners compared to healthy athletes. This pattern reflects a decline in neuromuscular efficiency, reduced functional stability, and slower execution of motor skills. The results highlight the need for targeted training and rehabilitation interventions to improve frequency-domain parameters and enhance dynamic stability in athletes with a history of ACL injury.
Type of Study: Research |
Subject:
Sport Science
Received: 2025/05/29 | Accepted: 2025/12/3 | Published: 2026/03/3
Received: 2025/05/29 | Accepted: 2025/12/3 | Published: 2026/03/3
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