Age-related changes in gait coordination are focused on the step-to-step transition

This study examined age-related changes in lower extremity coordination during gait using a unique gait phase normalization method, allowing time-continuous analysis while preserving phase-specific differences. Ten young and ten older healthy adults walked on an instrumented treadmill at their Preferred Walking Speed (PWS). Continuous Relative Phase (CRP) was used to assess intralimb and interlimb coordination and its variability across the gait cycle. Results showed that while older adults maintained largely similar coordination patterns to younger adults, significant differences emerged during transitions from double to single support. Specifically, older adults demonstrated altered hip-knee and interlimb knee coordination, driven by an earlier phase transition in knee phase angle during loading response and a delayed transition in hip phase angle during pre-swing. These alterations were accompanied by increased variability in interlimb hip coordination, particularly during critical gait transitions. Our findings suggest that age-related coordination changes are subtle and primarily affect step-to-step transitions. These changes may contribute to previously reported decreases in PWS, shorter step length, and increased metabolic cost in older adults. Future research should examine the relationship between these coordination changes and the age-related decline in PWS and increased metabolic cost of walking, as both are key consequences of altered step-to-step transitions.