Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB T2N 1N4, Canada.
Department of Health and Physical Education, Mount Royal University, Calgary, AB T3E 6K6, Canada.
J Sport Health Sci. 2022 May;11(3):293-302. doi: 10.1016/j.jshs.2020.12.007. Epub 2021 Jan 10.
This study aimed to investigate if changing the midsole bending stiffness of athletic footwear can affect the onset of lower limb joint work redistribution during a prolonged run.
Fifteen trained male runners (10-km time of <44 min) performed 10-km runs at 90% of their individual speed at lactate threshold (i.e., when change in lactate exceeded 1 mmol/L during an incremental running test) in a control and stiff shoe condition on 2 occasions. Lower limb joint kinematics and kinetics were measured using a motion capture system and a force-instrumented treadmill. Data were acquired every 500 m.
Prolonged running resulted in a redistribution of positive joint work from distal to proximal joints in both shoe conditions. Compared to the beginning of the run, less positive work was performed at the ankle (approximately 9%; p ≤ 0.001) and more positive work was performed at the knee joint (approximately 17%; p ≤ 0.001) at the end of the run. When running in the stiff shoe condition, the onset of joint work redistribution at the ankle and knee joints occurred at a later point during the run.
A delayed onset of joint work redistribution in the stiff condition may result in less activated muscle volume, because ankle plantar flexor muscles have shorter muscles fascicles and smaller cross-sectional areas compared to knee extensor muscles. Less active muscle volume could be related to previously reported decreases in metabolic cost when running in stiff footwear. These results contribute to the notion that footwear with increased stiffness likely results in reductions in metabolic cost by delaying joint work redistribution from distal to proximal joints.
本研究旨在探讨改变运动鞋中底弯曲刚度是否会影响下肢关节工作重新分布的起始时间，即在长时间跑步过程中。
15 名训练有素的男性跑步者（10 公里用时<44 分钟）在 2 次试验中，以个人乳酸阈速度的 90%（即递增跑步测试中乳酸变化超过 1mmol/L 时），在控制和硬底鞋条件下进行 10 公里跑步。使用运动捕捉系统和测力跑步机测量下肢关节运动学和动力学。每 500 米采集一次数据。
长时间跑步导致在两种鞋类条件下，从远端关节到近端关节重新分配正关节功。与跑步开始时相比，踝关节的正功减少了约 9%（p≤0.001），膝关节的正功增加了约 17%（p≤0.001）。在硬底鞋条件下跑步时，踝关节和膝关节的关节功重新分布的起始时间更晚。
在硬底鞋条件下，关节功重新分布的起始时间延迟可能导致肌肉激活量减少，因为与膝伸肌相比，踝关节跖屈肌的肌纤维更短，横截面积更小。肌肉激活量减少可能与之前报道的在硬底鞋中跑步时代谢成本降低有关。这些结果表明，增加刚度的鞋类可能通过延迟从远端关节到近端关节的关节功重新分布来降低代谢成本。
