Schepens B, Bastien G J, Heglund N C, Willems P A
Unité de Physiologie et Biomécanique de la Locomotion, Université Catholique de Louvain, 1 Place Pierre de Coubertin, B-1348 Louvain-la-Neuve, Belgium.
J Exp Biol. 2004 Feb;207(Pt 4):587-96. doi: 10.1242/jeb.00793.
The effect of age and body size on the total mechanical work done during walking is studied in children of 3-12 years of age and in adults. The total mechanical work per stride (W tot) is measured as the sum of the external work, W ext (i.e. the work required to move the centre of mass of the body relative to the surroundings), and the internal work, W int (i.e. the work required to move the limbs relative to the centre of mass of the body, W int,k, and the work done by one leg against the other during the double contact period, W int,dc). Above 0.5 m s(-1), both W ext) and W int,k, normalised to body mass and per unit distance (J kg(-1) m(-1)), are greater in children than in adults; these differences are greater the higher the speed and the younger the subject. Both in children and in adults, the normalised W int,dc shows an inverted U-shape curve as a function of speed, attaining a maximum value independent of age but occurring at higher speeds in older subjects. A higher metabolic energy input (J kg(-1) m(-1)) is also observed in children, although in children younger than 6 years of age, the normalised mechanical work increases relatively less than the normalised energy cost of locomotion. This suggests that young children have a lower efficiency of positive muscular work production than adults during walking. Differences in normalised mechanical work, energy cost and efficiency between children and adults disappear after the age of 10.
研究了年龄和体型对3至12岁儿童及成人行走过程中总机械功的影响。每步的总机械功（W tot）通过外部功W ext（即身体质心相对于周围环境移动所需的功）与内部功W int（即肢体相对于身体质心移动所需的功W int,k以及双腿在双支撑期相互作用的功W int,dc）之和来测量。速度高于0.5 m s(-1)时，按体重和单位距离归一化后的W ext和W int,k在儿童中比在成人中更大；速度越高且受试者年龄越小，这些差异就越大。在儿童和成人中，归一化后的W int,dc均呈现出随速度变化的倒U形曲线，其最大值与年龄无关，但出现在年龄较大受试者的较高速度下。在儿童中也观察到较高的代谢能量输入（J kg(-1) m(-1)），不过在6岁以下儿童中，归一化后的机械功增加幅度相对小于归一化后的运动能量消耗。这表明幼儿在行走过程中产生正向肌肉功的效率低于成人。儿童和成人在归一化机械功、能量消耗和效率方面的差异在10岁以后消失。
