Older adults produce joint moments less economically than young adults

Older adults expend more metabolic energy than young adults during walking (worse walking economy). Amid the numerous physiological changes that accompany advanced aging, the mechanisms governing the age-related decline in walking economy remain unestablished. Due to conflicting evidence, we studied whether older adults produce lower-limb joint moments less economically than young adults, independent of an age-related difference in muscle co activation. Eight older adults (71.6 ± 6.0 years) and 13 young adults (23.1 ± 4.7 years) repeatedly produced hip and ankle moment cycles on a dynamometer following visual feedback and an audible metronome. We instructed participants to produce moments with peak net torque values of 20 and 30 Nm at a 0.75 Hz cycle frequency and a 0.5 duty cycle. Overall, young and older adults did not co-activate their antagonist muscles differently during the moment production trials. At the hip, older adults expended more metabolic power than young adults despite producing lower moment amplitudes. At the ankle, older adults expended more metabolic power than young adults while producing non-different moment production cycles. Because older adults produced lower-limb joint moments less economically than young adults, interventions aimed at prolonging youthful walking economy into advanced age may need to directly address changing muscle-tendon unit physiology.