Climbing as a possible selective pressure shaping the human gluteus maximus: An investigation using musculoskeletal modeling and electromyography




Dias, Rae

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Differences between humans and extant apes in the pelvis and its key muscle attachment sites are thought to reflect a trade-off between arboreal and bipedal locomotor abilities. Human pelvic morphology enables the hamstrings to effectively power the hip hyperextension necessary for efficient bipedal locomotion, but this morphology is thought to reduce the capacity of these muscles to powerfully extend the hip when in a flexed position typical of arboreal locomotion. This research tested whether the enlarged human gluteus maximus may have been shaped by the continued importance of climbing among humans, as it has been suggested that it plays a compensatory role during powerful hip extension due to the reduced ability of the hamstrings. Musculoskeletal modeling and electromyography were used to assess the relative function of the gluteus maximus and the hamstrings in a human participant across two movement trials that required different amounts of hip extension: 1) bipedal walking, and 2) standing from a deep squat. It was hypothesized that the gluteus maximus would perform more effectively than the hamstrings to power hip extension from the flexed position of the squat. Differences in relative muscle activity across the two motions support this hypothesis in general, and implications for the evolutionary significance of the human gluteus maximus are that this muscle plays an important and likely compensatory role with the hamstrings during both standing up from a squat and bipedal walking. Results support the growing body of research that indicates that it is important to consider a broader range of human locomotive repertoires as of evolutionary significance, beyond solely terrestrial bipedal locomotion.



Evolution, Locomotion, Pelvis, Anthropology, Musculoskeletal modelling, Biomechanics, Electromyography