Bioenergetic basis for the increased fatigability with ageing.

Area of Science:

• Exercise Physiology
• Aging Research
• Skeletal Muscle Metabolism

Background:

• Age-related decline in physical function is common.
• Mechanisms behind increased fatigability in older adults during dynamic exercise are not fully understood.
• Skeletal muscle bioenergetics may play a crucial role.

Purpose of the Study:

• To investigate if age-related differences in skeletal muscle bioenergetics contribute to increased fatigability during dynamic exercise.
• To determine the association between metabolite accumulation and age-related fatigability.

Main Methods:

• Phosphorus magnetic resonance spectroscopy (31P-MRS) was used to measure high-energy phosphates and pH in the knee extensors of young and old adults.
• Muscle oxidative capacity was assessed via phosphocreatine (PCr) recovery kinetics.
• A dynamic knee extension exercise protocol was employed to induce fatigue.

Main Results:

• Muscle oxidative capacity did not differ between young and old adults.
• Fatigability was approximately 1.8-fold greater in older adults.
• Increased fatigability in older adults was associated with greater accumulation of inorganic phosphate (Pi) and diprotonated phosphate (H2PO4-) and a greater decrease in intracellular pH.

Conclusions:

• Age-related increases in fatigability during dynamic exercise are linked to impaired skeletal muscle bioenergetics.
• Greater accumulation of metabolites, specifically Pi and H2PO4-, and reduced pH contribute significantly to age-related muscle fatigue.
• These findings suggest a metabolic basis for reduced exercise capacity in older individuals.