Age-related gait adaptations in stair ascent: Changes in dynamic stability, coordination, and muscle activity in healthy adults

Objective Stair ascent, as a routine yet complex daily activity, imposes greater motor demands on older adults and is associated with an increased fall risk. Aging leads to gait adaptive changes; however, the gait adaptive changes during stair ascent across young adults, middle-aged adults, and older adults remain unclear. Methods This study employed a cross-sectional design and ultimately enrolled 36 healthy young adults, 36 middle-aged adults, and 36 older adults, with the oldest participants under 75 years of age. A three-dimensional motion analysis system combined with a surface electromyography system was used to collect gait data during stair ascent in all three groups, and differences in dynamic stability, joint coordination, and lower extremity muscle activation among the groups were further analyzed. Results Dynamic stability in the mediolateral direction during stair ascent was significantly lower in older adults than in young adults and middle-aged adults, and that trunk-pelvis transverse plane variability was significantly lower in older adults than in young adults. Regarding coordination modes, compared with young adults, middle-aged and older adults overall exhibited increased in-phase mode, decreased anti-phase mode, with lower-limb inter-joint coordination shifting toward greater proximal dominance and reduced distal dominance. Regarding muscle activation levels, older adults exhibited significantly higher activation of the medial gastrocnemius, biceps femoris, gluteus maximus, gluteus medius, and tibialis anterior than young and/or middle-aged adults. Conclusion These findings indicate that aging induces changes in coordination modes during stair ascent in middle-aged and older adults, and that the effects of aging on dynamic stability, coordination variability, and muscle function are more pronounced in older adults. This study was limited by its age range and cross-sectional design; therefore, the generalizability of the results to older adults of advanced age and their relationship with fall risk require further verification.