Leg asymmetries and coordination dynamics in walking

Models of interlimb coordination (H. Haken, J. A. S. Kelso, & H. Bunz, 1985; P. N. Kugler & M. T. Turvey, 1987) were tested in walking by examining the role of asymmetries between limbs. Participants walked on a treadmill with and without a metronome. Five asymmetry conditions were created via ankle loads of 0, 3, or 6 kg on either leg. With the metronome, participants matched the target period. Without the metronome, stride rate slowed as the mass was increased on either leg. The loads led to an increase in stride period that was predicted by Huygens' law and the hybrid pendulum-spring model. In agreement with extended Haken-Kelso-Bunz model predictions, leg asymmetries led to deviations from antiphase coordination. Also, perception-action coordination was influenced by the asymmetry between the legs and metronome. In contrast, no predicted stability effects were observed. These findings reveal that some properties of interlimb coordination, apparent in laboratory-based tasks, can also be observed in human walking.