Muscle forces and the demands of turning while walking.

Turning is a ubiquitous feature of human locomotion and like straight path walking, requires muscular force both to propel the individual forward and to stabilize the trunk over the stance limb. The purpose of this study is to identify muscle force patterns while making a turn and compare them to those of straight path walking. Kinematic and kinetic data were collected from 10 adults who walked unshod at their self-selected normal velocity in four conditions: straight line, 45° and 90° turns with a sidestep, and a 45° crossover event. A musculoskeletal model was used to calculate muscle forces in the pelvis and lower limb. Statistical parameter mapping (SPM) was used to determine whether the muscle force patterns of the three turning conditions were different from walking in a straight path. We find that, overall, the muscles that stabilize the hip and ankle during walking demonstrate differences in timing and magnitude of their force patterns across all turning conditions.