Power Training-induced Increases in Muscle Activation during Gait in Old Adults.

INTRODUCTION/PURPOSE: Aging modifies neuromuscular activation of agonist and antagonist muscles during walking. Power training can evoke adaptations in neuromuscular activation that underlie gains in muscle strength and power but it is unknown if these adaptations transfer to dynamic tasks such as walking. We examined the effects of lower-extremity power training on neuromuscular activation during level gait in old adults.

METHODS: Twelve community-dwelling old adults (age ≥ 65 yr) completed a 10-wk lower-extremity power training program and 13 old adults completed a 10-wk control period. Before and after the interventions, we measured maximal isometric muscle strength and electromyographic (EMG) activation of the right knee flexor, knee extensor, and plantarflexor muscles on a dynamometer and we measured EMG amplitudes, activation onsets and offsets, and activation duration of the knee flexors, knee extensors, and plantarflexors during gait at habitual, fast, and standardized (1.25 ± 0.6 m·s) speeds.

RESULTS: Power training-induced increases in EMG amplitude (~41%; 0.47 ≤ d ≤ 1.47; P ≤ 0.05) explained 33% (P = 0.049) of increases in isometric muscle strength (~43%; 0.34 ≤ d ≤ 0.80; P ≤ 0.05). Power training-induced gains in plantarflexor activation during push-off (+11%; d = 0.38; P = 0.045) explained 57% (P = 0.004) of the gains in fast gait velocity (+4%; d = 0.31; P = 0.059). Furthermore, power training increased knee extensor activation (~18%; 0.26 ≤ d ≤ 0.29; P ≤ 0.05) and knee extensor coactivation during the main knee flexor burst (~24%, 0.26 ≤ d ≤ 0.44; P ≤ 0.05) at habitual and fast speed but these adaptations did not correlate with changes in gait velocity.

CONCLUSIONS: Power training increased neuromuscular activation during isometric contractions and level gait in old adults. The power training-induced neuromuscular adaptations were associated with increases in isometric muscle strength and partly with increases in fast gait velocity.