Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada.
Department of Health and Physical Education, Mount Royal University, Calgary, AB, Canada.
Sci Rep. 2021 Jan 12;11(1):749. doi: 10.1038/s41598-020-80791-3.
In recent years, increasing the midsole bending stiffness (MBS) of running shoes by embedding carbon fibre plates in the midsole resulted in many world records set during long-distance running competitions. Although several theories were introduced to unravel the mechanisms behind these performance benefits, no definitive explanation was provided so far. This study aimed to investigate how the function of the gastrocnemius medialis (GM) muscle and Achilles tendon is altered when running in shoes with increased MBS. Here, we provide the first direct evidence that the amount and velocity of GM muscle fascicle shortening is reduced when running with increased MBS. Compared to control, running in the stiffest condition at 90% of speed at lactate threshold resulted in less muscle fascicle shortening (p = 0.006, d = 0.87), slower average shortening velocity (p = 0.002, d = 0.93) and greater estimated Achilles tendon energy return (p ≤ 0.001, d = 0.96), without a significant change in GM fascicle work (p = 0.335, d = 0.40) or GM energy cost (p = 0.569, d = 0.30). The findings of this study suggest that running in stiff shoes allows the ankle plantarflexor muscle-tendon unit to continue to operate on a more favourable position of the muscle's force-length-velocity relationship by lowering muscle shortening velocity and increasing tendon energy return.
近年来，通过在中底嵌入碳纤维板来增加跑鞋的中底弯曲刚度（MBS），导致许多长跑比赛中的世界纪录被打破。尽管引入了几种理论来揭示这些性能提升的机制，但到目前为止还没有明确的解释。本研究旨在探讨在 MBS 增加的鞋子中跑步时，小腿三头肌（GM）肌肉和跟腱的功能如何改变。在这里，我们首次提供了直接证据，表明 GM 肌肉肌纤维缩短的幅度和速度在 MBS 增加时会降低。与对照相比，在 90%速度乳酸阈下以最硬的条件跑步会导致肌肉肌纤维缩短减少（p=0.006，d=0.87），平均缩短速度较慢（p=0.002，d=0.93），估计跟腱能量返回更大（p≤0.001，d=0.96），而 GM 肌纤维做功（p=0.335，d=0.40）或 GM 能量消耗（p=0.569，d=0.30）没有显著变化。本研究的结果表明，在硬鞋中跑步可以通过降低肌肉缩短速度和增加肌腱能量返回，使踝关节跖屈肌-肌腱单元在肌肉力-长度-速度关系的更有利位置继续运作。
