Papachatzis Nikolaos, Slivka Dustin R, Pipinos Iraklis I, Schmid Kendra K, Takahashi Kota Z
Department of Biomechanics, University of Nebraska at Omaha, Omaha, NE, United States.
School of Health and Kinesiology, University of Nebraska at Omaha, Omaha, NE, United States.
Front Bioeng Biotechnol. 2022 Jun 27;10:908725. doi: 10.3389/fbioe.2022.908725. eCollection 2022.
Most of the terrestrial legged locomotion gaits, like human walking, necessitate energy dissipation upon ground collision. In humans, the heel mostly performs net-negative work during collisions, and it is currently unclear how it dissipates that energy. Based on the laws of thermodynamics, one possibility is that the net-negative collision work may be dissipated as heat. If supported, such a finding would inform the thermoregulation capacity of human feet, which may have implications for understanding foot complications and tissue damage. Here, we examined the correlation between energy dissipation and thermal responses by experimentally increasing the heel's collisional forces. Twenty healthy young adults walked overground on force plates and for 10 min on a treadmill (both at 1.25 ms) while wearing a vest with three different levels of added mass (+0%, +15%, & +30% of their body mass). We estimated the heel's work using a unified deformable segment analysis during overground walking. We measured the heel's temperature immediately before and after each treadmill trial. We hypothesized that the heel's temperature and net-negative work would increase when walking with added mass, and the temperature change is correlated with the increased net-negative work. We found that walking with +30% added mass significantly increased the heel's temperature change by 0.72 ± 1.91 ( = 0.009) and the magnitude of net-negative work (extrapolated to 10 min of walking) by 326.94 ± 379.92 J ( = 0.005). However, we found no correlation between the heel's net-negative work and temperature changes ( = 0.277). While this result refuted our second hypothesis, our findings likely demonstrate the heel's dynamic thermoregulatory capacity. If all the negative work were dissipated as heat, we would expect excessive skin temperature elevation during prolonged walking, which may cause skin complications. Therefore, our results likely indicate that various heat dissipation mechanisms control the heel's thermodynamic responses, which may protect the health and integrity of the surrounding tissue. Also, our results indicate that additional mechanical factors, besides energy dissipation, explain the heel's temperature rise. Therefore, future experiments may explore alternative factors affecting thermodynamic responses, including mechanical (e.g., sound & shear-stress) and physiological mechanisms (e.g., sweating, local metabolic rate, & blood flow).
大多数陆地有腿运动步态,如人类行走,在与地面碰撞时需要能量耗散。在人类中,脚跟在碰撞过程中大多进行净负功,目前尚不清楚它是如何耗散该能量的。根据热力学定律,一种可能性是净负碰撞功可能以热的形式耗散。如果得到证实,这一发现将为人类足部的体温调节能力提供信息,这可能对理解足部并发症和组织损伤有影响。在这里,我们通过实验性增加脚跟的碰撞力来研究能量耗散与热响应之间的相关性。20名健康的年轻成年人在测力板上在地面行走,并穿着带有三种不同附加质量水平(其体重的+0%、+15%和+30%)的背心在跑步机上行走10分钟(均以1.25米/秒的速度)。我们在地面行走期间使用统一的可变形节段分析来估计脚跟的功。我们在每次跑步机试验前后立即测量脚跟的温度。我们假设在增加质量行走时脚跟的温度和净负功会增加,并且温度变化与增加的净负功相关。我们发现,增加30%的质量行走显著使脚跟的温度变化增加了0.72±1.91(P = 0.009),并使净负功的大小(外推至10分钟行走)增加了326.94±379.92焦耳(P = 0.005)。然而,我们发现脚跟的净负功与温度变化之间没有相关性(P = 0.277)。虽然这一结果反驳了我们的第二个假设,但我们的发现可能证明了脚跟的动态体温调节能力。如果所有的负功都以热的形式耗散,我们预计在长时间行走期间皮肤温度会过度升高,这可能会导致皮肤并发症。因此,我们的结果可能表明各种散热机制控制着脚跟的热力学响应,这可能保护周围组织的健康和完整性。此外,我们的结果表明,除了能量耗散之外,其他机械因素也解释了脚跟的温度升高。因此,未来的实验可能会探索影响热力学响应的其他因素,包括机械因素(如声音和剪切应力)和生理机制(如出汗、局部代谢率和血流)。