Abstract
The human gluteus maximus is a distinctive muscle in terms of size, anatomy and function compared to apes and other non-human primates. Here we employ electromyographic and kinematic analyses of human subjects to test the hypothesis that the human gluteus maximus plays a more important role in running than walking. The results indicate that the gluteus maximus is mostly quiescent with low levels of activity during level and uphill walking, but increases substantially in activity and alters its timing with respect to speed during running. The major functions of the gluteus maximus during running are to control flexion of the trunk on the stance-side and to decelerate the swing leg; contractions of the stance-side gluteus maximus may also help to control flexion of the hip and to extend the thigh. Evidence for when the gluteus maximus became enlarged in human evolution is equivocal, but the muscle's minimal functional role during walking supports the hypothesis that enlargement of the gluteus maximus was likely important in the evolution of hominid running capabilities.
Highlights
Bipedalism has long been considered a characteristic feature of the hominid lineage (Darwin, 1859), and recent fossil evidence suggests that the very earliest hominids may have been bipedal in some manner (Haile-Selassie, 2001; Zollikofer et al, 2005)
There has been no systematic comparison of gluteus maximus (GM) activity during walking and running, the available evidence has led to the proposal that enlargement and reorganization of the GM may have played a role in, and possibly were selected for, the evolution of human endurance running capabilities (Bramble and Lieberman, 2004)
As predicted by Hypothesis 1, the most salient characteristic of GM activity during locomotion is that the basic pattern and magnitude of GM contractions differ substantially between walking and running, as shown in Fig.·2 and Table·1
Summary
Bipedalism has long been considered a characteristic feature of the hominid lineage (Darwin, 1859), and recent fossil evidence suggests that the very earliest hominids may have been bipedal in some manner (Haile-Selassie, 2001; Zollikofer et al, 2005). Many aspects of the hominid musculoskeletal system, especially in the leg and foot, have undergone substantial reorganization for bipedal posture and locomotion (see Lovejoy, 1988; Aiello and Dean, 1990; Ward, 2002). One of these features may be the gluteus maximus (GM). This study compares GM activity, combined with trunk and hindlimb kinematics, during bipedal walking and running in humans to test several hypotheses about the function and evolution of this distinctive muscle
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