During walking, interlimb coordination involves the right and left legs working together to achieve a desired movement. Previously, dynamic treadmill walking has been shown to drive asymmetric gait changes in healthy young adults through selectively changing the speed of the whole treadmill. Currently, the coordination demands of this novel walking environment are unknown and must be understood prior to assessing dynamic treadmill walking in clinical populations. We investigated the interlimb coordination requirements of dynamic treadmill walking in ten healthy young adults. We quantified interlimb coordination changes as phase shift (timing of maximum cross-correlation between limb angle trajectories of the left and right legs), center of oscillation (limb angle at midstance), and center of oscillation difference (oscillation angle difference between legs). We found that phase shift in the Fast trial (i.e., 1.0m/s treadmill speed in first 50% of gait cycle, 0.5m/s in latter 50%) was significantly more positive (i.e., the right leg oscillates ahead of the left leg in time) than in the Slow, Accelerate, and Decelerate trials (all p<0.01). The Fast trial produced significantly positive center of oscillation values on the right leg, indicating that the right leg is oscillating about a more flexed axis than the left. Center of oscillation difference was similarly more positive during the Fast trial than in the Decelerate (p<0.01) and Slow (p<0.01) trials. These results exemplify that some forms of dynamic treadmill walking change interlimb coordination to a greater extent than others. After several minutes of dynamic treadmill walking, interlimb coordination is changed relative to baseline walking in the spatial domain (Fast and Decelerate conditions) and the temporal domain (Fast and Slow). Therefore, dynamic treadmill walking is tunable in both biomechanical and interlimb coordination parameters, creating a variety of options for restoring gait symmetry in asymmetric populations.
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