Training improves muscle oxidative capacity and oxygenation recovery kinetics in patients with chronic obstructive pulmonary disease
We studied 21 patients with chronic obstructive pulmonary disease aged [mean (SD)] 63 (10) years, with a mean forced expiratory volume in 1 s of 40 (6)% and a peak oxygen uptake of 67 (11)% of predicted values. Patients trained for 6 weeks on a cycle ergometer at high work-rates (WR). Near-infrared spectroscopy was used to obtain the time-constant of the deoxygenation recovery signal (τHbO2) during three constant WR exercise tests, one below and two above the lactic acidosis threshold (θL). Glycolytic and oxidative enzymes and lactate concentrations were assessed in muscle biopsies. The τHbO2 decreased significantly in all three constant WR tests: –18 (24)s, –20 (23) s and –13 (22) s, respectively. Endurance time increased in the higher WR tests, by 5.7 (4.8) min and 3.6 (2.7) min, respectively. The activity of citrate-synthase (CS) and creatine-kinase changed significantly from 20 (10) to 30 (13) µmol·min–1·g–1 and from 3.825 (950) to 3.402 (526) µmol·min–1·g–1, respectively. Training also improved significantly the mean response time of the on-transient of oxygen uptake (τ'V˙O2) of the below-θL test. We found significant correlations between changes in CS and changes in τHbO2, τ'V˙O2 and endurance time. We conclude that leg training accelerates the speed of re-oxygenation of the vastus lateralis muscle after exercise. This improvement is correlated to changes in the oxidative enzymes.