Background: Sex-based biomechanical differences during a drop vertical jump (DVJ) may explain the increased risk of anterior cruciate ligament injury in females. Video motion capture using artificial intelligence (VMocap) is a new method for accurate motion analysis. Purpose: To use VMocap to identify sex-based differences in biomechanics during a DVJ in Asian athletes. Study Design: Controlled laboratory study. Methods: A total of 63 female and 61 male Asian soccer players volunteered for this study in 2018. Participants performed a bilateral DVJ using VMocap, and the knee valgus angle (KVA), knee flexion angle (KFA), hip flexion angle (HFA), and lower leg anterior inclination angle (LAIA) were calculated from the motion capture data. These joint angles and inclination angles were evaluated at the time of highest point of the first jump (H1), initial contact (IC), maximum knee flexion (MKF), toe-off (TO), and highest point of the second jump (H2). The unpaired t test was used to compare sex-based differences. Results: At H1, the KVA in females showed more valgus (−2.9° vs −5.4°) and the LAIA in females was greater (29.1° vs 25.7°) versus males ( P < .01 for both). At IC, the KVA in females showed more valgus (−1.3° vs −3.0°) and females had a greater KFA (20.8° vs 14.3°) and LAIA (5.1° vs 0.0°) compared with males ( P < .01 for all). At MKF, female KVA showed more valgus (6.2° vs −9.5°), and females had greater LAIA (36.6° vs 34.6°), smaller KFA (77.5° vs 87.5°), and smaller HFA (55.8° vs 82.0°) compared with males ( P < .01 for all). At TO, female KVA showed more valgus (−0.7° vs −3.1°) and female KFA, HFA, and LAIA were greater (31.7° vs 19.2°; 19.9° vs 16.4°; and 18.2° vs 11.5°, respectively) than males ( P < .01 for all). At H2, females had a greater KFA (18.6° vs 14.6°) and LAIA (13.3° vs 9.9°) than males ( P < .04 for both). Conclusion: Asian female soccer players showed increased KVA and LAIA, decreased KFA and HFA at MKF, and increased KFA at IC and TO compared with their male counterparts in this analysis of the DVJ. Clinical Relevance: Elucidation of kinematic differences between the sexes can aid in predicting injuries.

Environmental factors, such as living in a barrier home, are critical for fall-related fractures, in addition to demographic and physical factors. A multidisciplinary approach that considers both physical and environmental factors is necessary for reducing the incidence of fall-related fractures among middle-aged and older Japanese adults. Geriatr Gerontol Int 2018; 18: 1372-1377.

Background: In soccer, the roles of the dominant (kicking) and nondominant (supporting) legs are different. The kinematic differences between the actions of the dominant and nondominant legs in female soccer players are not clear. Purpose: To clarify the kinematic differences between dominant and nondominant legs during a single-leg drop vertical jump (DVJ) in female soccer players. Study Design: Controlled laboratory study. Methods: A total of 64 female high school and college soccer players were included in this study. Participants performed a single-leg DVJ test utilizing video motion capture with artificial intelligence during the preseason period. This study assessed the knee flexion angles, knee valgus angles, hip flexion angles, and lower leg anterior inclination angle at 3 time points (initial contact, maximum flexion of the knee, and toe-off) and compared them between the dominant and nondominant legs. These angles were calculated from motion capture data and analyzed in 3 dimensions. A paired t test was used to analyze the differences between legs, and the significance level was set at P < .05. Results: The knee valgus angle at initial contact was greater in the nondominant leg (mean ± SD, 0.8°± 5.2°) than the dominant leg (−0.9°± 4.9°) ( P < .01). There were no differences between legs for any other angles at any of the time points. Conclusion: The kinematics of the dominant and nondominant legs of female soccer players in a single-leg DVJ differ in knee valgus angle. Clinical Relevance: Leg dominance is associated with the risk of sports injuries. Kinematic differences between the dominant and nondominant legs may be a noteworthy factor in elucidating the mechanisms and risk of sports injury associated with leg dominance.

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In this paper, we propose the analysis method for finding out the similarity of the muscle force patterns to mine the risk factor of the anterior cruciate ligament (ACL) injury. Akaike information criteria (AIC) under the assumption of the auto-regression model is adapted to analyze the similarities of muscle force patterns in time-series. The difference of AIC values between 2 muscles is considered to be the distance between 2 muscle force patterns and the dexterity of the maneuver is expected to be discussed. We measured drop vertical jump (DVJ) and use the data around the contact timing of whom hadn't had ACL injury experiments. The results showed that we could successfully calculate AIC distance according to the similarity of the time-series data pattern and it can be useful to discuss one's dexterity of controlling body maneuvers soon after contact timing of DVJ motion.