Muscle metabolic energy costs while modifying propulsive force generation during walking

Area of Science:

• Biomechanics
• Human Movement Science
• Gerontology

Background:

• Walking is a fundamental human activity, but its metabolic cost increases with age.
• Previous research suggests age-related changes in muscle function and joint mechanics contribute to this increased cost.
• Understanding these changes is crucial for developing interventions to maintain mobility in older adults.

Purpose of the Study:

• To investigate the hypothesis that age-related increases in walking metabolic cost are partly due to a redistribution of joint power.
• To examine how reduced peak propulsive forces (F_P) influence lower limb muscle metabolic costs in young adults.
• To determine if a distal-to-proximal redistribution of joint power is a key factor in elevated metabolic cost during aging.

Main Methods:

• Utilized targeted peak propulsive force (F_P) biofeedback in young adults.
• Employed musculoskeletal models to estimate the metabolic costs of lower limb muscles.
• Simulated walking across a range of F_P conditions to analyze joint power redistribution.

Main Results:

• Young adults exhibited a redistribution of joint power, similar to older adults, when walking with experimentally reduced F_P.
• Simulations indicated that muscles spanning the hip compensated for insufficient ankle push-off and smaller F_P.
• This compensatory mechanism leads to increased metabolic cost.

Conclusions:

• The study supports the theory of distal-to-proximal redistribution of joint power as a significant contributor to increased walking metabolic cost in older adults.
• Reduced peak propulsive forces (F_P) drive this compensatory joint power redistribution.
• Findings provide insights into the biomechanical factors underlying age-related declines in walking efficiency.