Raichlen David A
Department of Anthropology, University of Arizona, 1009 E. South Campus Drive, Tucson, AZ 85721, USA.
J Exp Biol. 2008 Sep;211(Pt 17):2767-72. doi: 10.1242/jeb.020073.
The dynamic similarity hypothesis (DSH) suggests that differences in animal locomotor biomechanics are due mostly to differences in size. According to the DSH, when the ratios of inertial to gravitational forces are equal between two animals that differ in size [e.g. at equal Froude numbers, where Froude = velocity2/(gravity x hip height)], their movements can be made similar by multiplying all time durations by one constant, all forces by a second constant and all linear distances by a third constant. The DSH has been generally supported by numerous comparative studies showing that as inertial forces differ (i.e. differences in the centripetal force acting on the animal due to variation in hip heights), animals walk with dynamic similarity. However, humans walking in simulated reduced gravity do not walk with dynamically similar kinematics. The simulated gravity experiments did not completely account for the effects of gravity on all body segments, and the importance of gravity in the DSH requires further examination. This study uses a kinematic model to predict the effects of gravity on human locomotion, taking into account both the effects of gravitational forces on the upper body and on the limbs. Results show that dynamic similarity is maintained in altered gravitational environments. Thus, the DSH does account for differences in the inertial forces governing locomotion (e.g. differences in hip height) as well as differences in the gravitational forces governing locomotion.
动态相似性假说（DSH）表明，动物运动生物力学的差异主要归因于体型差异。根据DSH，当两只体型不同的动物的惯性力与重力之比相等时[例如在相等的弗劳德数下，其中弗劳德数=速度²/（重力×臀高）]，通过将所有时间持续时间乘以一个常数、所有力乘以第二个常数以及所有线性距离乘以第三个常数，它们的运动可以变得相似。DSH得到了众多比较研究的普遍支持，这些研究表明，由于惯性力不同（即由于臀高变化作用在动物身上的向心力差异），动物行走具有动态相似性。然而，在模拟微重力环境中行走的人类并没有以动态相似的运动学方式行走。模拟重力实验并未完全考虑重力对身体所有节段的影响，并且重力在DSH中的重要性需要进一步研究。本研究使用运动学模型来预测重力对人类运动的影响，同时考虑重力对上半身和四肢的影响。结果表明，在改变的重力环境中动态相似性得以保持。因此，DSH确实考虑了支配运动的惯性力差异（例如臀高差异）以及支配运动的重力差异。
