Cavagna G A, Willems P A, Heglund N C
Istituto di Fisiologia Umana, Università degli Studi di Milano, 20133 Milan, Italy.
J Physiol. 2000 Nov 1;528(Pt 3):657-68. doi: 10.1111/j.1469-7793.2000.00657.x.
During walking on Earth, at 1.0 g of gravity, the work done by the muscles to maintain the motion of the centre of mass of the body (W(ext)) is reduced by a pendulum-like exchange between gravitational potential energy and kinetic energy. The weight-specific W(ext) per unit distance attains a minimum of 0.3 J x kg(-1) x m(-1) at about 4.5 km x h(-1) in adults. The effect of a gravity change has been studied during walking on a force platform fixed to the floor of an aircraft undergoing flight profiles which resulted in a simulated gravity of 0.4 and 1.5 times that on Earth. At 0.4 g, such as on Mars, the minimum W(ext) was 0.15 J x kg(-1) x m(-1), half that on Earth and occurred at a slower speed, about 2.5 km x h(-1). The range of walking speeds is about half that on Earth. At 1.5 g, the lowest value of W(ext) was 0.60 J x kg(-1) x m(-1), twice that on Earth; it was nearly constant up to about 4.3 km x h(-1) and then increased with speed. The range of walking speeds is probably greater than that on Earth. A model is presented in which the speed for an optimum exchange between potential and kinetic energy, the 'optimal speed', is predicted by the balance between the forward deceleration due to the lift of the body against gravity and the forward deceleration due to the impact against the ground. In conclusion, over the range studied, gravity increases the work required to walk, but it also increases the range of walking speeds.
在地球上行走时，重力为1.0g，肌肉为维持身体质心运动所做的功（W(ext)）通过重力势能和动能之间类似钟摆的交换而减少。在成年人中，每单位距离的体重特异性W(ext)在约4.5 km·h⁻¹时达到最小值0.3 J·kg⁻¹·m⁻¹。在固定于飞机地板上的力平台上行走时，研究了重力变化的影响，该飞机的飞行剖面导致模拟重力为地球重力的0.4倍和1.5倍。在0.4g时，如在火星上，最小W(ext)为0.15 J·kg⁻¹·m⁻¹，是地球上的一半，且出现在较慢的速度，约2.5 km·h⁻¹。行走速度范围约为地球上的一半。在1.5g时，W(ext)的最低值为0.60 J·kg⁻¹·m⁻¹，是地球上的两倍；在约4.3 km·h⁻¹之前几乎保持恒定，然后随速度增加。行走速度范围可能大于地球上的。提出了一个模型，其中通过身体对抗重力抬起时的向前减速与撞击地面时的向前减速之间的平衡来预测势能和动能之间最佳交换的速度，即“最佳速度”。总之，在所研究的范围内，重力增加了行走所需的功，但也增加了行走速度范围。
