Quadriceps strength in patients with chronic obstructive pulmonary disease.

BACKGROUND: Skeletal muscle dysfunction is well known in chronic obstructive pulmonary disease (COPD). The muscle strength is altered in various muscles variedly. Lower-limb muscle strength is very important for walking distance. Reduced lower-limb strength can affect the physical quality of life. OBJECTIVES: The aim of the study was to assess and compare the quadriceps strength in COPD patients and age-matched healthy controls and to study the correlation between lung function parameters and the quadriceps strength in patients with COPD. METHODOLOGY: Thirty nonsmoker male patients; thirty nonsmoker female patients with COPD; and sixty age-, BMI-, and gender-matched healthy controls were studied. Quadriceps muscle strength was measured using a quadriceps dynamometer. Forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), FEF 25-75, and peak expiratory flow rate were measured using Helios 702 Spirometer. The quadriceps muscle strength between the two groups was compared using the unpaired Student's t-test. Correlations between FVC and FEV1with muscle strength were analyzed using the Pearson's coefficient. RESULTS: The mean unilateral and bilateral quadriceps strength in both male and female COPD patients was significantly lesser than the healthy controls (P < 0.05). There was a significant positive correlation between muscle strength and FVC and muscle strength and FEV1in patients with COPD. CONCLUSION: The study shows that there is quadriceps weakness in COPD patients, and pulmonary functions have a direct impact on skeletal muscle strength. Identifying those patients who have reduced strength will allow early interventions targeted at improving the quality of life of the patient.