RELATIONSHIP OF RESPIRATORY AND QUADRICEPS MUSCLE STRENGTH TO THE EXERCISE CAPACITY IN CHRONIC OBSTRUCTIVE PULMONARY DISEASE PATIENTS

Abstract

PURPOSE: To study the relationship among respiratory and lower limb muscle strength and exercise capacity in patients with chronic obstructive pulmonary disease(COPD). METHODS: We studied 15 patients with COPD (9 men, 64.4 ± 8.2 years). All patients performed spirometry and assessment of respiratory muscle strength. Quadriceps strength and endurance was evaluated by the one-repetition maximum test (1RM) and one-minute sit-to-stand test. The exercise capacity was assessed through the six-minute walk test. RESULTS: Mean forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1) and FVC/FEV1 were 70.7 ± 16.9%, 42.6 ± 19.5% and 47.2 ± 13.6, respectively. The maximal inspiratory pressure (PImax) was -78.2 ± 24.4 cmH2O and the maximal expiratory pressure (PEmax) was 98.5 ± 26.4 cmH2O. The mean values of 1RM test and sit-to-stand test were 17.2 ± 7.4 kg and 26.4 ± 5.1 repetitions, respectively. The walked distance was 426 ± 68.1 m. The walked distance was associated with PImax (r = -0.615; p = 0.01) and PEmax (r = 0.641; p = 0.01); there was no association between walked distance and quadriceps muscle strength (p = 0.50). CONCLUSION: We conclude that maximal respiratory pressures but not quadriceps muscle strength correlated with the exercise performance measured by walked distance in COPD patients. CLINICAL IMPLICATIONS: Further studies are needed to understand the influence of respiratory and quadriceps muscle strength on exercise performance in COPD patients.