In the present study we calculated the muscle fascicle length (MFL) and the physiological cross-sectional area (PCSA) in the elbow flexor muscles of five Homo sapiens and five Pan troglodytes . We also assessed the expression of the myosin heavy chain (MyHC) isoforms with real-time quantitative polymerase chain reaction in the same muscles and, finally, we analyzed the muscle insertion sites in the proximal epiphyses of the ulna and the radius with 3D geometric morphometrics. Our main objective is to identify quantitative differences in the elbow flexor muscles of Homo sapiens and Pan troglodytes in terms of muscle architecture, expression of MyHC isoforms, and bone insertion sites and to explore the association of these differences with the types of locomotion developed by these two species of hominoid primates. We observed that the elbow flexor muscles had a greater PCSA and a higher expression of the fast MyHC-II isoforms in Pan troglodytes , while they had a greater MFL and a higher expression of the slow MyHC-I isoform in Homo sapiens . The insertion site of the brachialis was larger in Pan troglodytes , while that of the biceps brachii was larger in Homo sapiens . Our findings may be related to the greater capacity of force generation in the elbow flexor muscles of Pan troglodytes , as an adaptation to vertical climbing, and to the greater contraction speed and resistance to fatigue of the muscles in Homo sapiens , as an adaptation to the manipulative function of the upper extremities.

中文翻译：

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现代人和普通黑猩猩肘屈肌的结构和分子分析

在本研究中，我们计算了五个智人和五个泛穴居人的肘部屈肌的肌肉束长度 (MFL) 和生理横截面积 (PCSA)。我们还通过实时定量聚合酶链反应评估了肌球蛋白重链 (MyHC) 同种型在相同肌肉中的表达，最后，我们使用 3D 几何形态计量学分析了尺骨近端骨骺和桡骨的肌肉插入位点. 我们的主要目标是在肌肉结构、MyHC 亚型的表达和骨插入部位方面确定人类和泛穴居人肘部屈肌的数量差异，并探索这些差异与这些差异发展的运动类型之间的关联。两种人科灵长类动物。我们观察到肘部屈肌在 Pan troglodytes 中具有更大的 PCSA 和更高的快速 MyHC-II 同种型的表达，而它们在智人中具有更大的 MFL 和更高的慢 MyHC-I 同种型的表达。Pan troglodytes的肱肌插入部位较大，而智人的肱二头肌的插入部位较大。我们的发现可能与 Pan troglodytes 肘部屈肌产生更大的力的能力有关，作为对垂直攀爬的适应，以及与智人的肌肉更快的收缩速度和抗疲劳能力有关，作为对垂直攀爬的适应。上肢的操纵功能。而他们在智人中具有更大的 MFL 和更高的慢 MyHC-I 同种型表达。Pan troglodytes的肱肌插入部位较大，而智人的肱二头肌的插入部位较大。我们的发现可能与 Pan troglodytes 肘部屈肌产生更大的力的能力有关，作为对垂直攀爬的适应，以及与智人的肌肉更快的收缩速度和抗疲劳能力有关，作为对垂直攀爬的适应。上肢的操纵功能。而他们在智人中具有更大的 MFL 和更高的慢 MyHC-I 同种型表达。Pan troglodytes的肱肌插入部位较大，而智人的肱二头肌的插入部位较大。我们的发现可能与 Pan troglodytes 肘部屈肌产生更大的力的能力有关，作为对垂直攀爬的适应，以及与智人的肌肉更快的收缩速度和抗疲劳能力有关，作为对垂直攀爬的适应。上肢的操纵功能。