Age differences in knee extension power, contractile velocity, and fatigability

Area of Science:

• Gerontology
• Exercise Physiology
• Biomechanics

Background:

• Aging is associated with declines in muscle strength and power.
• Understanding age-related changes in specific muscle performance is crucial for maintaining function in older adults.
• Previous research has not fully elucidated age-related differences in muscle power adjusted for muscle mass.

Purpose of the Study:

• To investigate age and gender differences in knee extensor strength, power, and fatigue.
• To test if specific strength (strength per unit muscle mass) differs by age.
• To determine if age-related deficits in specific power and fatigue are linked to reduced maximal contractile velocity.

Main Methods:

• Skeletal muscle performance was assessed in young and older adults using open- and closed-chain tests.
• Measurements included one-repetition maximum strength, concentric knee extensor peak power, velocity, and fatigability.
• Thigh lean mass (TLM) was measured using dual-energy X-ray absorptiometry to calculate specific strength and power.

Main Results:

• Specific strength for knee extension was lower in older adults (32.4 N/kg TLM) compared to young adults (41.2 N/kg TLM).
• Specific power remained significantly lower in older adults (25-41% less) even after adjusting for TLM.
• Older adults exhibited greater knee extensor fatigue, with peak velocity decreasing by 24% over 10 repetitions.

Conclusions:

• Deficits in concentric power and increased fatigability in older adults persist after accounting for thigh lean mass.
• Reduced maximal contractile velocity with aging is a key factor contributing to performance decline.
• Velocity impairments may contribute to mobility loss and increased fall risk in older adults, suggesting interventions targeting contractile velocity are needed.