Comparison of ground reaction forces and antagonist muscle coactivation during stair walking with ageing

Stair walking is a demanding task in old age. Ground reaction force (GRF) analysis, relative EMG activation, and muscular coactivation were performed during stair walking. The aim was to investigate the ageing effect on GRF distribution and muscle antagonist coactivation during stair walking, at varied speed. During ascending at maximal velocity old subjects demonstrated reduced GRF in all examined phases (range: 28–35%), whereas muscle coactivation only was elevated for the Entire stance phase (18.5%). GRF parameters during ascent and descent at freely chosen speed demonstrated differences between age groups (5–28%). Furthermore, muscle coactivation was elevated in old subjects (e.g. Entire stance phase (17–19%)) along with greater EMG activation in all muscles (16–65%). At standardized gait velocity only minor differences in GRF were observed between age groups. However, elderly subjects showed elevated muscular coactivation (e.g. loading phase and entire stance phase (18–22%)) along with greater EMG activation (35–66%).Conclusions: Differences between age groups in neuromotor and kinetic stair walking strategy do not depend upon the age-related decline in velocity alone, but rather reflect a uniform alteration. This needs to be considered during rehabilitation and/or clinical settings at old age.