In addition to the respiratory limitation in patients with chronic obstructive pulmonary disease
(COPD), skeletal muscle abnormalities may occur and contribute to the exercise intolerance. This study assessed the ability of the skeletal muscle of patients with COPD to adapt to individualized exercise training
at the gas exchange threshold
Fourteen patients (8 in a training group and 6 controls) performed the following exercise tests before and after a 3-week training period: an incremental exercise test, maximal voluntary contraction of the quadriceps, and three endurance tests consisting of dynamic contractions of the quadriceps until exhaustion. These endurance tests, characterized by three different power outputs, were used to determine muscle limit times and critical power
The results showed that training increased exercise tolerance (+ 11% for symptom limited peak oxygen consumption [VO2
sl], P < 0.05), maximum voluntary contraction (+ 8%, P < 0.05), limit times (from + 45% to + 161%, P < 0.05) and critical power
(+ 39%, P < 0.05).
These findings indicate greater muscle strength and endurance after training in COPD patients and suggest better muscular recruitment and improved oxidative capacity in the exercising muscles. The sharp differences in the magnitude of VO2
sl and limit times suggest that the kinetics of peripheral and central changes in response to training are different. In conclusion, peripheral muscle performance can be increased rapidly in response to an individualized training program at the GET in COPD patients.