High-Intensity Interval Alternating Concentric-Eccentric Training in Chronic Respiratory Disease

Chronic respiratory diseases, particularly chronic obstructive pulmonary disease (COPD), are commonly associated with exercise intolerance, dyspnea, peripheral muscle dysfunction, and reduced quality of life. Although exercise training is a central component of pulmonary rehabilitation, patients may have difficulty tolerating conventional high-intensity exercise because of ventilatory limitation and leg fatigue. Eccentric exercise can generate relatively high mechanical workloads with lower oxygen consumption and cardiopulmonary demand than concentric exercise. High-intensity interval training (HIIT), on the other hand, is an effective approach for improving aerobic capacity. This study therefore investigates whether incorporating eccentric cycling into the recovery periods of HIIT can provide additional skeletal muscle stimulation without substantially increasing cardiopulmonary stress. This is a single-center, prospective, randomized controlled trial conducted at Fu Jen Catholic University Hospital. Forty-five adults with chronic respiratory disease who have participated in pulmonary rehabilitation for more than 3 months will be enrolled and randomly allocated to three groups, with approximately 15 participants in each group: (1) high-intensity interval alternating concentric-eccentric training, (2) high-intensity interval concentric training, or (3) usual care. Before randomization, participants will undergo graded exercise testing, functional performance assessments, and questionnaires. Participants assigned to the exercise groups will complete supervised training for 12 weeks. The alternating concentric-eccentric group will also undergo an eccentric exercise familiarization period before the formal training program. Participants in the usual-care group will continue routine care with self-regulated exercise intensity for 12 weeks. After the intervention, graded exercise testing, functional assessments, and questionnaires will be repeated. The study will evaluate changes in functional performance, exercise capacity, muscle function, symptoms, and quality of life to determine whether alternating concentric-eccentric HIIT provides additional benefits compared with conventional concentric HIIT and usual care.