Effects of Low-Load/High-Repetition Resistance Training on Exercise Capacity, Health Status, and Limb Muscle Adaptation in Patients With Severe COPD A Randomized Controlled Trial

BACKGROUND: Training volume is paramount in the magnitude of physiological adaptations following resistance training. However, patients with severe COPD are limited by dyspnea during traditional two-limb low-load/high-repetition resistance training (LLHR-RT), resulting in suboptimal training volumes. During a single exercise session, single-limb LLHR-RT decreases the ventilatory load and enables higher localized training volumes compared with two-limb LLHR-RT. RESEARCH QUESTION: Does single-limb LLHR-RT lead to more profound effects compared with two-limb LLHR-RT on exercise capacity (6-min walk distance [6MWD]), health status, muscle function, and limb adaptations in patients with severe COPD? STUDY DESIGN AND METHODS: Thirty-three patients (mean age 66 +/- 7 years; FEV1 39 +/- 10% predicted) were randomized to 8 weeks of single- or two-limb LLHR-RT. Exercise capacity (6MWD), health status, and muscle function were compared between groups. Quadriceps muscle biopsy specimens were collected to examine physiological responses. RESULTS: Single-limb LLHR-RT did not further enhance 6MWD compared with two-limb LLHR-RT (difference, 14 [-12 to 39 m]. However, 73% in the single-limb group exceeded the known minimal clinically important difference of 30 m compared with 25% in the two-limb group (P = .02). Health status and muscle function improved to a similar extent in both groups. During training, single-limb LLHR-RT resulted in a clinically relevant reduction in dyspnea during training compared with two-limb LLHR-RT (-1.75; P = .01), but training volume was not significantly increased (23%; P = .179). Quadriceps muscle citrate synthase activity (19%; P = .03), hydroxyacyl-coenzyme A dehydrogenase protein levels (32%; P < .01), and capillary-to-fiber ratio (41%; P < .01) were increased compared with baseline after pooling muscle biopsy data from all participants. INTERPRETATION: Single-limb LLHR-RT did not further increase mean 6MWD compared with two-limb LLHR-RT, but it reduced exertional dyspnea and enabled more people to reach clinically relevant improvements in 6MWD. Independent of execution strategy, LLHR-RT improved exercise capacity, health status, muscle endurance, and enabled several physiological muscle adaptations, reducing the negative consequences of limb muscle dysfunction in COPD.

Automated summary

This study examined the effects of single-limb low-load/high-repetition resistance training (LLHR-RT) compared to two-limb LLHR-RT on exercise capacity, health status, muscle function, and limb adaptations in patients with severe COPD. Single-limb LLHR-RT did not significantly increase 6-minute walk distance (6MWD) compared to two-limb LLHR-RT, but it did reduce exertional dyspnea and enable more patients to reach clinically relevant improvements in 6MWD. Both training methods improved exercise capacity, health status, muscle function, and led to physiological muscle adaptations in COPD patients.