Assessment of knee extensor and flexor function using isokinetic test in COPD: impact on exercise capacity

Area of Science:

• Pulmonary Rehabilitation
• Exercise Physiology
• Musculoskeletal Function

Background:

• Chronic Obstructive Pulmonary Disease (COPD) is characterized by airflow limitation and reduced exercise capacity.
• Lower-limb muscle dysfunction, including weakness and endurance deficits, is common in COPD patients and contributes to exercise limitation.
• Understanding the specific contributions of knee extensor and flexor muscles to exercise capacity is crucial for targeted interventions.

Purpose of the Study:

• To quantify the relationship between knee extensor and flexor strength and endurance and exercise capacity in patients with COPD.
• To identify specific muscle function parameters that are significantly associated with exercise capacity measures in COPD.

Main Methods:

• A cross-sectional study involving 108 stable COPD patients.
• Isokinetic testing was used to evaluate knee extensor and flexor strength and endurance.
• Exercise capacity was assessed using the 6-minute walking test (6MWT) and the 30-second sit-to-stand test (30s SST).
• Multiple regression analysis was employed to determine the associations between muscle function and exercise capacity.

Main Results:

• Multiple regression analysis revealed that flexor total work, extensor endurance ratio, age, and FEV1% predicted were significantly associated with 6MWT performance (adjusted R² = 0.455, P < 0.001).
• Flexor total work and age were significantly associated with 30s SST performance (adjusted R² = 0.355, P < 0.001).
• These findings indicate that knee muscle function, especially endurance, plays a significant role in determining exercise capacity in COPD.

Conclusions:

• Knee muscle endurance demonstrates a significant relationship with exercise capacity in patients with COPD.
• Knee flexor endurance appears to be a particularly important factor contributing to overall exercise capacity in this population.
• These results suggest that interventions targeting knee flexor endurance may be beneficial for improving exercise capacity in COPD management.