Department of Mechanical Engineering & Materials Science, Yale University, New Haven, Connecticut, United States of America.
Department of Biomechanics, University of Nebraska at Omaha, Omaha, Nebraska, United States of America.
PLoS One. 2023 Sep 11;18(9):e0286521. doi: 10.1371/journal.pone.0286521. eCollection 2023.
When humans walk on slopes, the ankle, knee, and hip joints modulate their mechanical work to accommodate the mechanical demands. Yet, it is unclear if the foot modulates its work output during uphill and downhill walking. Therefore, we quantified the mechanical work performed by the foot and its subsections of twelve adults walked on five randomized slopes (-10°, -5°, 0°, +5°, +10°). We estimated the work of distal-to-hindfoot and distal-to-forefoot structures using unified deformable segment analysis and the work of the midtarsal, ankle, knee, and hip joints using a six-degree-of-freedom model. Further, using a geometric model, we estimated the length of the plantar structures crossing the longitudinal arch while accounting for the first metatarsophalangeal wrapping length. We hypothesized that compared to level walking, downhill walking would increase negative and net-negative work magnitude, particularly at the early stance phase, and uphill walking would increase the positive work, particularly at the mid-to-late stance phase. We found that downhill walking increased the magnitude of the foot's negative and net-negative work, especially during early stance, highlighting its capacity to absorb impacts when locomotion demands excessive energy dissipation. Notably, the foot maintained its net dissipative behavior between slopes; however, the ankle, knee, and hip shifted from net energy dissipation to net energy generation when changing from downhill to uphill. Such results indicate that humans rely more on joints proximal to the foot to modulate the body's total mechanical energy. Uphill walking increased midtarsal's positive and distal-to-forefoot negative work in near-equal amounts. That coincided with the prolonged lengthening and delayed shortening of the plantar structures, resembling a spring-like function that possibly assists the energetic demands of locomotion during mid-to-late stance. These results broaden our understanding of the foot's mechanical function relative to the leg's joints and could inspire the design of wearable assistive devices that improve walking capacity.
当人类在斜坡上行走时，踝关节、膝关节和髋关节会调节它们的机械功以适应力学需求。然而，目前尚不清楚足部在上下坡行走时是否会调节其功输出。因此，我们量化了 12 位成年人在 5 个随机坡度（-10°、-5°、0°、+5°、+10°）上行走时足部及其各部分的机械功。我们使用统一的可变形节段分析来估计远-跟骨和远-前足结构的功，使用六自由度模型来估计中跗关节、踝关节、膝关节和髋关节的功。此外，我们使用几何模型，在考虑第一跖趾关节包裹长度的情况下，估计了穿过纵弓的足底结构的长度。我们假设与平地行走相比，下坡行走会增加负功和净负功的幅度，尤其是在早期站立阶段，而上坡行走会增加正功，尤其是在中晚期站立阶段。我们发现，下坡行走增加了足部负功和净负功的幅度，尤其是在早期站立阶段，这突出了其在运动需求过度能量耗散时吸收冲击的能力。值得注意的是，足部在不同坡度之间保持了其净耗散行为；然而，当从下坡变为上坡时，踝关节、膝关节和髋关节从净能量耗散转变为净能量产生。这些结果表明，人类更多地依赖于足部近端的关节来调节身体的总机械能。上坡行走增加了中跗关节的正功和远-前足的负功，幅度大致相等。这与足底结构的延长和缩短延迟相吻合，类似于弹簧样的功能，可能有助于中晚期站立时的运动能量需求。这些结果拓宽了我们对足部相对于腿部关节的机械功能的理解，并可能激发可穿戴辅助设备的设计，以提高行走能力。
