Does kinematic coupling in the lower extremities and trunk during a chair transfer task change between younger and older adulthood?

BACKGROUND: Past work examining relationships across biomechanical domains during gait has observed that age-related effects may be dependent on the joint of interest. This work has not been extended to other functional tasks, nor to relationships within the kinematic domain. RESEARCH QUESTION: How does kinematic coupling between the lower extremity and trunk segments during a functional task (sit-stand-sit) differ between younger and older adults? METHODS: Younger (n = 21) and older (n = 28) adults performed a sit-stand-sit task while whole-body motion was tracked. Sagittal foot, shank, thigh, and trunk segment angles were calculated and cross-correlated between pairings of adjacent segments (foot-shank, shank-thigh, and thigh-trunk). Maximum cross-correlation coefficients and their temporal lags quantified the strength and timing of coupling, respectively, and were compared between age groups. RESULTS: Where significant differences were identified, foot-shank and thigh-trunk cross-correlation coefficients were generally stronger, and temporal lags were generally shorter, for older and younger adults, respectively. The thigh-trunk pairing exhibited the opposite trend during the sit-down phase, with stronger cross-correlation coefficients observed for older adults. SIGNIFICANCE: These joint-dependent trends may be an indicator of the use of compensatory strategies during sit-stand-sit, which may aid in identifying older adults who could benefit from interventions to prevent functional declines in the ability to perform chair transfer tasks.