Effect of 12 weeks of interval training on skeletal muscle blood flow during single-leg knee extensor exercise in COPD: a non-randomized controlled trial

High-intensity interval training (HIIT) has shown to improve exercise capacity, symptom burden, and quality of life in patients with chronic obstructive pulmonary disease (COPD), but it remains to be investigated if HIIT can counteract limb muscle dysfunction. Therefore, we examined the impact of a 12-wk supervised HIIT protocol on muscle oxygen conductance. Eight patients with mild-to-moderate COPD and eight age-, sex-, and BMI-matched controls underwent a 12-wk HIIT intervention. Leg blood flow ([Formula: see text]) and arterio-venous blood samples were collected at rest and during active single-leg knee-extensor exercise (KEE) at unloaded (0 W) and 20% of peak workload (WLpeak) to estimate leg muscle oxygen conductance pre- and post-HIIT. In pre-HIIT, [Formula: see text] was similar between groups during unloaded KEE (P = 0.108) but lower at 20% WLpeak in the COPD group, compared with the control group. [Formula: see text] responses were higher during unloaded KEE (28%, P = 0.012) and 20% WLpeak (40%, P < 0.001) post-HIIT in the COPD group, whereas no change occurred in the control group. Flow-adjusted skeletal muscle O2 conductance was higher in the COPD pre-HIIT group but only increased in the control group. Thus, there was no difference in diffusive or convective capacity between groups post-HIIT at submaximal KEE. COPD assessment score decreased by 2.8 [1;4] (P = 0.003) in the COPD group and V̇o2peak increased in both groups (COPD 192 mL O2/min, P = 0.032, control 257 mL O2/min, P = 0.004) with no time/group interaction. A 12-wk HIIT intervention may improve peripheral exercise capacity in COPD by increasing the vasodilatory function in working muscle while concurrently improving whole-body exercise capacity and symptom burden.NEW & NOTEWORTHY Individuals with COPD exhibit lower blood flow to the exercising leg muscles, which may be considered part of the limb muscle dysfunction associated with the disease. A 12-wk high-intensity interval training (HIIT) program increased leg blood flow in patients with COPD during single-leg knee extensor exercise achieved by improving the vasodilatory response. HIIT also improved maximal oxygen uptake and exercise capacity while reducing symptom burden.