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首页> 外文期刊>Journal of Biomechanics >Optimum ratio of upper to lower limb lengths in hand-carrying of a load under the assumption of frequency coordination.
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Optimum ratio of upper to lower limb lengths in hand-carrying of a load under the assumption of frequency coordination.

机译：在频率协调的假设下，手动搬运负载时上下肢长度的最佳比例。

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The ratio of the upper to lower limb lengths [or the intermembral index (IMI)] in the earliest human ancestors is closer to that of the living chimpanzees than to our own, although the former show undoubted adaptations to bipedality. What biomechanical factors could then have led to the phenomenon of genus Homo? This paper proposes and evaluates a relationship between IMI and hand-carrying. Assuming that coordination of limb swing frequencies of the upper and lower limbs would be the subject of positive selection, a mathematical expression was derived and can in part explain the changes in IMI. We found that AL-288-1 [3.6 million years old (MY)], the most complete skeleton of the early hominid Australopithecus afarensis, could only have carried loads equivalent to 15-50% of the upper limb weight while maintaining swing symmetry, but KNM WT-15000, Homo ergaster (1.8MY) and modern humans could both carry loads 3 times heavier than the upper limb while maintaining swing symmetry. The carrying ability of chimpanzees would be inferior to that of AL-288-1. The IMI of modern humans, at 68-70, is the smallest, and is optimal for hand-carrying under our criteria. Under reduced selection pressure for hand-carrying, but unreduced selection for mechanical effectiveness, we might expect humans to evolve a longer upper limb, to improve swing symmetry when unloaded.
机译：在最早的人类祖先中，上肢和下肢的长度之比[或跨膜间指数（IMI）]比我们的黑猩猩更接近于活着的黑猩猩，尽管前者无疑显示出对两足动物的适应性。那么哪些生物力学因素会导致人属现象呢？本文提出并评估了IMI和随身携带之间的关系。假设上肢和下肢的肢体摆动频率的协调将是正面选择的主题，则推导了数学表达式，并且可以部分解释IMI的变化。我们发现AL-288-1 [360万岁（MY）]是早期人类原始南方古猿Afarensis的最完整骨架，在维持挥杆对称性的同时，它只能承受相当于上肢重量15％至50％的载荷，但是KNM WT-15000，Her ergaster（1.8MY）和现代人在保持摆动对称性的同时，都可以承受比上肢重3倍的载荷。黑猩猩的携带能力不如AL-288-1。现代人的IMI为68-70，是最小的，并且在我们的标准下最适合手持。在降低手提压力的同时，在降低机械效率的选择压力下，我们可以期望人类进化出更长的上肢，从而在卸载时提高挥杆的对称性。

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