Impact of age on muscle and kinematic responses to an obstacle trip while walking

INTRODUCTION: This study examined the impact of age on muscle and kinematic responses to an obstacle trip while walking. MATERIALS AND METHODS: 102 older (65-90 years) and 26 young (21-35 years) people were unexpectedly tripped using a pop-up obstacle that contacted their left foot while walking on an 8-m walkway. Kinematics and lower limb muscle responses during the first and second recovery steps were measured. RESULTS: Following a trip, older people more often lowered their tripped foot before the obstacle and fell into the harness, compared to young (P < 0.05). When the tripped foot was immediately lifted over the obstacle, older people showed greater co-contraction of ankle muscles and faster peak activation of plantar-flexors but slower, shorter and lower recovery steps than young (P < 0.01). When the tripped foot was immediately lowered, despite similar muscle responses, older people took shorter and lower steps to clear the obstacle and were less stable than young (P < 0.01). CONCLUSIONS: Lower-limb muscle responses to an obstacle trip in older people may be quick but inefficient (co-contraction), resulting in poorer recovery steps and more falls compared to young people. Exercise interventions should aim to improve muscle capacity and motor skills required to prevent falls following unexpected trips.