Reduced knee extensor function in heart failure is not explained by inactivity.

Area of Science:

• Cardiology
• Exercise Physiology
• Muscle Physiology

Background:

• Heart failure (HF) is a complex syndrome affecting multiple organ systems.
• Skeletal muscle dysfunction is a recognized complication of HF.
• The specific impact of HF on knee extensor muscle contractile properties remains incompletely understood.

Purpose of the Study:

• To investigate whether heart failure alters knee extensor muscle torque, power production, or contractile velocity.
• To compare contractile performance between individuals with HF and age- and sex-matched controls.

Main Methods:

• Evaluated knee extensor contractile performance (isometric and isokinetic) in HF patients (n=11) and controls (n=11).
• Assessed body composition using dual-energy X-ray absorptiometry.
• Matched groups for age, sex, and physical activity level (measured by accelerometry).

Main Results:

• HF patients showed significantly lower isometric knee extensor torque (21-29%) and peak concentric torque (15-33%) compared to controls.
• Peak power output was reduced in HF patients, corresponding to torque deficits.
• Group differences in torque were eliminated when normalized to isometric capacity, indicating impaired intrinsic muscle force generation.

Conclusions:

• Muscle contractile dysfunction in HF patients was independent of age, sex, body composition, and physical activity levels.
• The findings suggest that the heart failure syndrome itself, rather than secondary factors, underlies the observed deficits in muscle contractile function.