Peripheral muscle mass and function can be impaired in patients with mild chronic obstructive pulmonary disease (COPD). Quadriceps cross-sectional area is reduced in these patients compared to controls [1], particularly in those with dyspnea as compared to non-dyspneic counterparts and smoker controls [2]. Reduced physical activity is closely related to peripheral muscle mass in mild COPD [1], suggesting that early therapeutic interventions are needed in this group of patients. In addition, reduced quadriceps mass is strongly associated to quadriceps weakness [3,4] and a substantial proportion of patients with mild COPD (28%) had quadriceps weakness [5]. Reduced muscle mass and resultant muscle weakness contribute to limiting exercise in COPD [6-8] and to reduce physical activity, particularly in mild disease [1].~Exercise training (ET) is widely used in patients with moderate-to-very-severe COPD to improve peripheral muscle function and thus exercise capacity and quality of life [9]. Unfortunately, the effects of ET in mild COPD are currently unclear. A recent systematic review identified three low-quality studies with different designs (retrospective, one group pre-posttest, and one randomized controlled trial) [10]. The authors found significant improvements in exercise capacity (effect size 0.87-1.82) and quality of life (effect size 0.24-0.86) after comparing pretest-posttest data and ET with usual care. Although these results are inconclusive and indicate that additional and more robust studies should be conducted [10], current recommendations to initiate ET include even mild disease if dyspnea or exercise limitation are present [11]. Since peripheral muscle mass and function improve with ET [9], the investigators hypothesize that this statement is correct and consequently ET will increase exercise capacity in dyspneic patients with mild COPD in comparison to usual care.~Patients will enter an 8-week ET program of 3 days per week supervised exercise training at the Rehabilitation Physiotherapy Gymnasium. Exercise training will include high-intensity endurance training at 60-80% of baseline peak work rate and strength training of upper and lower limbs with 3 sets of 6 repetitions at 50% of one repetition maximum [12,13]. Each session will be 60 min duration, 30 min dedicated to cycle exercise. The UC group will receive usual outpatient care and follow-up.~The study will require 30 patients per arm to detect an effect size of 0.88 [10] at the 5% significance level and with 80% power, allowing a dropout rate of 30%.
The primary aim of this clinical study is to investigate if exercise training can improve exercise capacity and quality of life in dyspneic mild chronic obstructive pulmonary disease patients.