Abstract
Part 1 of this article outlined the extensive osseous adaptations around the hip that occurred in the development of a habitual bipedal gait in modern humans. The shortest summary of these osseous changes is ‘double extension’, i.e. extension of both the hip joint and the lumbar spine. Not surprisingly, these osseous changes went hand in hand with major muscular changes. The primary changes that accompanied the double extension were changes in relative muscle volume for the quadriceps, gluteus maximus and hamstrings, changes in moment arms for the iliopsoas, gluteus maximus and hamstrings, a change in function for the gluteus medius and minimus, while the functional anatomy of the adductors and hip rotators changed only slightly. The effect of these osseous and muscular changes was improved energy efficiency of human bipedal walking and (long distance) running. However, this occurred at the expense of maximum power, characteristic for activities such as tree climbing (in the apes), but equally so for sprinting. Recognizing these changes and their consequences may help us better understand and treat soft-tissue disorders around the hip.
Highlights
No mammal has a habitual extended hip joint position like humans do
Part 1 of this article outlined the extensive osseous adaptations around the hip that occurred in the development of a habitual bipedal gait in modern humans
The primary changes that accompanied the double extension were changes in relative muscle volume for the quadriceps, gluteus maximus and hamstrings, changes in moment arms for the iliopsoas, gluteus maximus and hamstrings, a change in function for the gluteus medius and minimus, while the functional anatomy of the adductors and hip rotators changed only slightly. The effect of these osseous and muscular changes was improved energy efficiency of human bipedal walking and running. This occurred at the expense of maximum power, characteristic for activities such as tree climbing, but so for sprinting
Summary
No mammal has a habitual extended hip joint position like humans do. Other mammals, including the non-human apes (i.e. gibbon, chimpanzee, bonobo, gorilla and orangutan), have a ‘mid-flex’ hip position as their default. The hamstrings and gluteus maximus in chimpanzees, for example, have a relatively long muscle moment arm at the hip and a short lever (i.e. the femur) to move. The lever for hamstrings and gluteus maximus (the femur) is lengthened, while the muscle moment arms (at hip and/or knee) are shortened, decreasing the power generating capacity of the muscles.
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