Stiffness of ankle joint has been investigated in a wide range of biomechanical studies with a focus on the improvement of performance and reduction in the risk of injury. However, measuring ankle joint stiffness (AJS) using the existing conventional methodologies requires sophisticated equipment such as force plate and motion analyses systems. This study presents a novel method for measuring AJS during a hopping task with no force or motion measurement system. Also the validity of the proposed new method was investigated by comparing the results against those obtained using conventional method in which motion capture and force plate data are used. Twelve participants performed the controlled hopping task at 2.2 Hz, on a force platform, and six high speed cameras recorded the movement. To calculate the AJS in both methods, the lower extremity was modeled as a three linked rigid segments robot with three joints. In the new method, the contact time and flight time were used to calculate ground reaction force, and inverse kinematic and inverse dynamic approaches were used to calculate the ankle kinematic and kinetic. The AJS calculated using the new method was compared against the results of conventional method as the reference. The calculated AJS using this new method (506.47 ± 177.84 N·m/rad) showed a significant correlation (r = 0.752) with the AJS calculated using conventional method (642.39 ± 185.96 N·m/rad). The validation test showed a mean difference of −24.76% using Bland–Altman plot. The presented method can be used as a valid, and low-cost tool for assessing AJS in the field in low resource settings.
Purpose: Core stability and leg stiffness are two determinant mechanisms in athletic performance and risk injury. This study aimed to investigate the gender differences and relationship of these two factors in athletes. Methods:In this cross-sectional study, core stability and leg stiffness of 12 male and 12 female Iranian squash players at national level were examined utilizing McGill's test (including flexor, extensor, left side bridge and right side bridge tests) and hopping test at 2.2 Hz. Total core stability was calculated by integrating its 4 parts and their ratios which were considered as balance criteria of core stability. Leg stiffness was normalized to body mass. Independent t test and Pearson correlation test were performed to investigate the research purposes. All statistical analyses were done using SPSS 16.0. Results:The core stability in two groups had no significant difference. However, the female group had more unbalanced core stability than male group. Leg stiffness was higher in male group than the female group but this difference disappeared after normalizing body mass. The significant correlation between core stability and leg stiffness was explored (r=0.46, P=0.02). Conclusion:Although the female participants of the study achieved the same scores as males, their unbalanced core and possible adopted strategy to compensate their less stiff structures, may expose them to greater injury risk. These results are noteworthy for designing training programs and choosing proper movement strategies. The significant, but weak correlation between variables indicates the power transmitting role of core musculature in leg stiffness regulation during hopping that should be considered.
Introduction: With respect to the prevalence of chronic ankle instability and adverse consequences such as neuromuscular dysfunction of the proximal joints, implementation of preventive proceeding in proximal joints of ankle is very necessary. Therefore, the present study aims to investigate the Effect of six weeks plyometric training with feedback on maximum knee flexion and maximum vertical GRF on drop landing technique of male basketball players with chronic ankle instability. Material and Methods: The present study has a quasi-experimental research design. Twenty-four male basketball players with chronic ankle instability participated in this study. After identifying individuals using questionnaires Cumberland, athletes into two groups (n = 12) and control group (n = 12) were divided. Evaluation of maximum knee flexion and maximum vertical ground reaction force were conducted using ten cameras and two distinct forces, respectively. The participants in experimental group performed plyometric training with feedback for six weeks. After examining the normality of data by Shapiro-wilk test, paired t-test was used to compare within groups and independent t-test was used to compare between groups. Results: The results of the statistical study showed six weeks plyometric training with feedback on maximum knee flexion and maximum vertical GRF on drop landing technique of male basketball players with chronic ankle instability, and significantly increases maximum knee flexion( p=0/001) and reduce the maximum vertical GRF( p=0/001). Conclusion: Adding plyometric exercises with feedback to the program of basketball players with chronic ankle instability can improve the technique of landing in the knee joint flexion and reduce the grand reaction force and reduce the risk of injury to the knee and ankle joints.
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