Voloshina Alexandra S, Ferris Daniel P
School of Kinesiology, University of Michigan, Ann Arbor, MI, USA Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, USA
School of Kinesiology, University of Michigan, Ann Arbor, MI, USA.
J Exp Biol. 2015 Mar;218(Pt 5):711-9. doi: 10.1242/jeb.106518. Epub 2015 Jan 23.
In the natural world, legged animals regularly run across uneven terrain with remarkable ease. To gain understanding of how running on uneven terrain affects the biomechanics and energetics of locomotion, we studied human subjects (N=12) running at 2.3 m s(-1) on an uneven terrain treadmill, with up to a 2.5 cm height variation. We hypothesized that running on uneven terrain would show increased energy expenditure, step parameter variability and leg stiffness compared with running on smooth terrain. Subject energy expenditure increased by 5% (0.68 W kg(-1); P<0.05) when running on uneven terrain compared with smooth terrain. Step width and length variability also increased by 27% and 26%, respectively (P<0.05). Positive and negative ankle work decreased on uneven terrain by 22% (0.413 J kg(-1)) and 18% (0.147 J kg(-1)), respectively (P=0.0001 and P=0.0008). Mean muscle activity increased on uneven terrain for three muscles in the thigh (P<0.05). Leg stiffness also increased by 20% (P<0.05) during running on uneven terrain compared with smooth terrain. Calculations of gravitational potential energy fluctuations suggest that about half of the energetic increases can be explained by additional positive and negative mechanical work for up and down steps on the uneven surface. This is consistent between walking and running, as the absolute increases in energetic cost for walking and running on uneven terrain were similar: 0.68 and 0.48 W kg(-1), respectively. These results provide insight into how surface smoothness can affect locomotion biomechanics and energetics in the real world.
在自然界中，有腿动物能够轻松自如地在崎岖不平的地形上奔跑。为了了解在不平坦地形上奔跑如何影响运动的生物力学和能量学，我们对12名人类受试者进行了研究，他们在一台不平坦地形跑步机上以2.3米/秒的速度奔跑，高度变化最大可达2.5厘米。我们假设，与在平坦地形上奔跑相比，在不平坦地形上奔跑会表现出能量消耗增加、步幅参数变异性增加和腿部刚度增加。与在平坦地形上奔跑相比，受试者在不平坦地形上奔跑时能量消耗增加了5%（0.68瓦/千克；P<0.05）。步宽和步长的变异性也分别增加了27%和26%（P<0.05）。在不平坦地形上，正向和负向踝关节功分别减少了22%（0.413焦/千克）和18%（0.147焦/千克）（P=0.0001和P=0.0008）。大腿上三块肌肉在不平坦地形上的平均肌肉活动增加（P<0.05）。与在平坦地形上奔跑相比，在不平坦地形上奔跑时腿部刚度也增加了20%（P<0.05）。重力势能波动的计算表明，大约一半的能量增加可以通过在不平坦表面上上下步时额外的正向和负向机械功来解释。这在行走和奔跑之间是一致的，因为在不平坦地形上行走和奔跑时能量消耗的绝对增加是相似的：分别为0.68和0.48瓦/千克。这些结果为表面平整度如何在现实世界中影响运动生物力学和能量学提供了见解。
