二木 康夫

Purpose The full‐body kinematic chain plays a crucial role in golf swings, and trunk muscle fatigue may significantly affect swing mechanics. This study aimed to investigate how trunk muscle fatigue influences trunk and lower limb kinematics during golf swings. Methods Eleven healthy adult golfers (mean age: 20.3 ± 0.8 years) participated in a pre–post experimental study conducted in a biomechanics laboratory with a grass‐simulated hitting surface. Participants performed golf swings with a 7‐iron before and after undergoing a trunk muscle fatigue protocol involving plank exercises. Three‐dimensional kinematic data of the trunk and lead‐side lower limbs were recorded. Results Following the fatigue protocol, trunk sagittal plane stability significantly decreased (pre: 47.9°, post: 43.4°, p   < 0.01). Ankle range of motion also declined in both the sagittal plane (34.5° to 30.0°, p   < 0.05) and frontal plane (15.8° to 12.3°, p   < 0.01). Although total lower limb joint moments remained unchanged, the relative contribution of frontal‐plane ankle moments significantly decreased (15.6% 12.6%, p   < 0.05). Conclusion Trunk muscle fatigue reduces trunk stability and ankle mobility during golf swings. Increased lower limb stiffness may act as a compensatory strategy to maintain swing mechanics under fatigued conditions.

PURPOSE: Graft-notch impingement and large graft bending angle (GBA) in anterior cruciate ligament reconstruction (ACLR) carry a risk of graft failure and subsequent poor postoperative outcomes. Most studies have analyzed the impingement rate and GBA using computed tomography (CT) in the supine position, but not in the standing condition. This study aimed to assess the graft impingement and GBA using upright multi-detector CT (MDCT). METHODS: We analyzed 43 knee joints of 23 healthy volunteers (women, n = 13; men, n = 10) in a single-leg standing position using an upright 320-detector-row CT. We defined the putative position of the graft tunnel in three-dimensional models and assessed the impingement rate and GBA of both the anteromedial (AMB) and posterolateral bundles (PLB). RESULT: The impingement rate for the AMB with a 6-mm graft diameter (81.4 %) was significantly higher than that for the PLB (0.7 %; P < 0.001). The modified AMB tunnel position, which connects the midpoint between the traditional AM and PL tunnel apertures of the femur to the most medial point within the tibial AM footprint, reduced the impingement rate by 14.0 % (P < 0.001). The impingement rate of the modified AMB with a 10-mm graft diameter (32.6 %) was significantly lower than that of the traditional AMB with a 6-mm graft diameter (81.4 %; P < 0.001). The GBA of the modified AMB was significantly smaller than that of the traditional AMB (P < 0.001). CONCLUSION: This study indicated high graft-notch impingement rates and large GBA for traditional AMB in the standing position, highlighting potential biomechanical challenges associated with traditional double-bundle ACLR configurations.