Zhang Zhenyuan, Lake Mark
School of Sport and Exercise Science, Liverpool John Moores University, Liverpool, United Kingdom.
Front Sports Act Living. 2022 Apr 26;4:824183. doi: 10.3389/fspor.2022.824183. eCollection 2022.
Midsole cushioning thickness (MT) is a key component of running footwear that may influence the stiffness setting of the joints, performance enhancement, and injury prevention. Most studies that have investigated the influence of manipulating shoe midsole characteristics on foot strike patterns and vertical force loading rates have not considered the dynamic conditions of initial landing and the associated initial lower limb joint stiffness. In this study, we examined the effect of running in shoes with large changes in MT on both the posture and dynamics associated with foot strike.
12 injury-free runners with habitual rearfoot strike patterns ran at 4.5 m/s along a 40-m runway in shoe conditions with MT of 30, 42, and 54 mm, respectively. Ground reaction force and the right leg kinematic data were collected. One-way repeated measures ANOVA was conducted to statistically analyze the effect of MT on key variables linked to foot strike.
Increased midsole thickness resulted in a slightly flatter foot strike posture ( < 0.05), a decreased shank retraction velocity ( < 0.05), and an increase in forward horizontal foot velocity ( < 0.05), all at initial ground contact. Vertical force loading rates were reduced with increasing MT ( < 0.05), but this was associated with large increases in the initial ankle and knee joint stiffness ( < 0.05).
Adjustments in the initial conditions of contact with the ground during running were seen in both the posture and dynamics of the lower limbs. To help to mitigate the impact severity from foot-ground collision with the thinnest shoe condition, there was an increased shank retraction velocity and decreased forward velocity of the foot at landing. These active impact-moderating adaptations likely served to reduce the changes in impact severity expected due to midsole material properties alone and should be considered in relation to altering the risk of running-related injuries.
中底缓冲厚度（MT）是跑鞋的一个关键组成部分，可能会影响关节的刚度设定、提高运动表现和预防损伤。大多数研究在探究操纵鞋中底特性对足部着地模式和垂直力加载率的影响时，并未考虑初始着地的动态条件以及相关的初始下肢关节刚度。在本研究中，我们考察了穿着MT有大幅变化的鞋子跑步对与足部着地相关的姿势和动力学的影响。
12名习惯后足着地模式且无损伤的跑步者分别穿着MT为30、42和54毫米的鞋子，以4.5米/秒的速度沿40米跑道跑步。收集地面反作用力和右腿运动学数据。进行单因素重复测量方差分析，以统计学方式分析MT对与足部着地相关的关键变量的影响。
中底厚度增加导致在初始地面接触时足部着地姿势稍变平（P<0.05）、小腿后缩速度降低（P<0.05）以及足部向前水平速度增加（P<0.05）。随着MT增加，垂直力加载率降低（P<0.05），但这与初始踝关节和膝关节刚度大幅增加有关（P<0.05）。
在跑步过程中，下肢的姿势和动力学在与地面接触的初始条件方面均出现了调整。为了帮助减轻在最薄鞋底条件下足部与地面碰撞的冲击严重程度，着地时小腿后缩速度增加且足部向前速度降低。这些主动的减轻冲击的适应性变化可能有助于减少仅因中底材料特性而预期的冲击严重程度变化，并且在考虑改变与跑步相关损伤的风险时应予以考虑。
