Department of Human Physiology, University of Oregon, Eugene, OR, USA.
Department of Human Physiology, University of Oregon, Eugene, OR, USA.
Hum Mov Sci. 2019 Oct;67:102501. doi: 10.1016/j.humov.2019.102501. Epub 2019 Jul 22.
Altering the longitudinal bending stiffness of footwear has the potential to affect mechanics of the metatarsophalangeal (MTP) joint. Recent efforts have been put forth to identify an optimal bending stiffness of footwear to improve running performance. However, little is known about how this optimal bending stiffness may change with running speed. The purpose of this study was to investigate how dynamic angular stiffness about the MTP joint changes across running speeds. Eighteen participants ran at five speeds from 3.89 to 6.11 m/s. Metatarsophalangeal joint angles, moments, and stiffness were estimated for each speed. Two MTPJ load-displacement metrics were defined, active and critical stiffness. Instantaneous stiffness of the MTP joint was also quantified. There was a significant main effect of speed on critical stiffness (p < .001), maximum MTP moment (p < .001), MTP moment at maximum dorsiflexion (p < .001), and MTP range of motion (p = .013). There was no effect of speed on active stiffness (p = .094). These results support the notion that involvement of the MTP joint increases with running speed. Individual contributions of the foot and shoe to the MTP joint moment and stiffness suggest that the foot appears to dominate the stiffness of the foot-shoe complex and torque generation about the MTP joint. Instantaneous stiffness fluctuated throughout stance phase, suggesting that foot-shoe complex stiffness is time dependent. The ratio by which critical stiffness and MTP joint range of motion increase with running speed may provide insight for how to guide construction of performance footwear. These results suggest that when utilizing MTP joint mechanics for insights into designing a shoe for performance purposes, the effect of speed should be taken into consideration.
改变鞋类的纵向弯曲刚度有可能影响跖趾关节（MTP）的力学。最近已经做出了一些努力来确定改善跑步性能的鞋类最佳弯曲刚度。然而，对于这个最佳弯曲刚度如何随着跑步速度而变化，人们知之甚少。本研究的目的是调查 MTP 关节的动态角刚度如何随跑步速度而变化。18 名参与者以 3.89 至 6.11 m/s 的五个速度跑步。为每个速度估计了 MTP 关节的角度、力矩和刚度。定义了两个 MTPJ 载荷-位移指标，即主动刚度和临界刚度。还量化了 MTP 关节的瞬时刚度。速度对临界刚度（p < 0.001）、最大 MTP 力矩（p < 0.001）、最大背屈时 MTP 力矩（p < 0.001）和 MTP 运动范围（p = 0.013）有显著的主效应。速度对主动刚度没有影响（p = 0.094）。这些结果支持了 MTP 关节参与度随跑步速度增加的观点。足部和鞋子对 MTP 关节力矩和刚度的个体贡献表明，足部似乎主导着足鞋复合体的刚度和 MTP 关节的扭矩产生。瞬时刚度在整个站立阶段波动，表明足鞋复合体的刚度是时间依赖的。临界刚度和 MTP 关节运动范围随跑步速度增加的比率可能为如何指导性能鞋类的构建提供一些见解。这些结果表明，当利用 MTP 关节力学来深入了解为性能目的设计鞋子时，应考虑速度的影响。
