Meeting Abstract
Human bipedal walking entails unique frontal plane balance strategies compared to other primates. Compared to bipedal chimpanzees, humans walk with step widths that are proportionally three times narrower, utilize stance-phase hip adduction rather than abduction, and use a pattern of pelvic drop on the swing side rather than swing-side pelvic elevation. Here we sought to determine if and how the human-like pattern of pelvic and hip motion is related to step width. To investigate pelvic and hip motion during walking, ten human subjects walked on a treadmill at narrow, normal, and wide step widths. Full body kinematics were measured using the Plug-In Gait marker set with a 12-camera Vicon motion capture system. Our results suggest that neither wide steps (~3 times normal width) nor narrow steps (~0 cm) lead to major differences in pelvic list. Narrow and wide steps do lead to an increase and decrease, respectively, in overall hip adduction (+3° for narrow steps, -6° for wide steps). These results suggest that the human-like pattern of pelvic list is not dependent on step width, though hip adduction is. The change to pelvic drop on the swing side in humans and perhaps some early hominins was therefore likely an evolved trait, and not a direct result of the emergence of valgus knees and narrow step widths.
