Older adults produce joint moments less economically than young adults.

Older adults expended more metabolic power than young adults at the hip despite producing lower moment amplitudes.

• Eight older adults (71.6 ± 6.0 yr) and 13 young adults (23.1 ± 4.7 yr) were studied
• Participants produced hip moment cycles on a dynamometer following visual feedback and an audible metronome
• Moment production was performed at peak net torque values of 20 and 30 Nm at 0.75 Hz cycle frequency with a 0.5 duty cycle
• Despite producing lower moment amplitudes, older adults had higher metabolic power at the hip

Older adults expended more metabolic power than young adults at the ankle while producing nondifferent moment production cycles.

• Ankle moment cycles were produced on a dynamometer at the same target torque values (20 and 30 Nm) and cycle parameters (0.75 Hz, 0.5 duty cycle)
• The moment production cycles at the ankle were not statistically different between older and young adults
• Despite similar ankle moment output, older adults consumed more metabolic power
• This finding indicates worse economy of ankle moment production in older adults independent of differences in moment amplitude

Young and older adults did not coactivate their antagonist muscles differently during the moment production trials.

• Muscle coactivation was measured during dynamometer-based hip and ankle moment production tasks
• The study was designed to test whether age-related differences in joint moment economy exist independent of muscle coactivation differences
• No statistically significant difference in antagonist muscle coactivation was found between the two age groups
• This finding rules out coactivation as the primary explanation for the observed difference in moment economy between age groups

The study concluded that less economical muscle-tendon unit force production in older adults likely contributes to their greater metabolic energy expenditure during walking.

• The authors argue that interventions aimed at prolonging youthful walking economy into advanced age may need to directly address changing muscle-tendon unit physiology
• The study isolated joint moment production from walking to test economy independent of gait mechanics
• The finding is described as noteworthy because the mechanisms governing age-related decline in walking economy had previously been elusive
• Results held across both hip and ankle joints, suggesting a generalized age-related deficit in the economy of lower-limb moment production

The study used a dynamometer-based protocol with visual feedback and auditory metronome to isolate lower-limb joint moment production from confounds present during walking.

• Participants produced cyclic hip and ankle moments at 0.75 Hz with a 0.5 duty cycle
• Two target peak net torque levels were used: 20 Nm and 30 Nm
• Visual feedback and an audible metronome were used to standardize moment production
• This design allowed assessment of metabolic cost of moment production independent of age-related differences in gait mechanics or walking speed