Effects of age and walking speed on coactivation and cost of walking in healthy adults

Our goal was to determine how age and walking speed affect metabolic cost of walking (C_w), lower, extremity antagonist coactivation, and relationships between coactivation and C_w in healthy, active, individuals. Fourteen young (25 ± 3 years) and 14 older (71 ± 4 years) participants walked on a treadmill at, four speeds (0.89, 1.12, 1.34, and 1.57 m s^-1) while electromyography (EMG) and oxygen consumption, were measured. Coactivation indices were calculated for musculature about the thigh and shank. C_w, was higher in older adults across all speeds (p < 0.001). Coactivation about the thigh was also higher in, older adults (p < 0.001), whereas coactivation about the shank was not different between age groups (p = 0.60). Total coactivation (thigh coactivation plus shank coactivation) showed significant positive, relationships to C_w at all walking speeds (r = 0.46-0.57). Higher C_w and coactivation in older adults, along with the positive relationship between C_w and coactivation implies coactivation contributes to, higher C_w of older adults.