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

ABSTRACT 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 sub-optimal training volumes. During a single exercise session, single-limb LLHR-RT decreases the ventilatory load and enables higher localized training volumes compared to two-limb LLHR-RT. Research question Does single-limb LLHR-RT lead to more profound effects when compared to two-limb LLHR-RT on exercise capacity (6-minute walk distance [6MWD]), health status, muscle function and limb intramuscular adaptations in patients with severe COPD? Study design and methods Thirty-three patients (66±7 years; FEV1 39±10% pred) were randomized to eight-weeks of single- or two-limb LLHR-RT. Exercise capacity (6MWD), health status, and muscle function were compared between groups. Quadriceps muscle biopsies were collected to examine physiological responses. Results Single-limb LLHR-RT did not further enhance 6MWD when compared to two-limb (Δ14 [-12 to 39m]. However, 73% in the single-limb group exceeded the known minimal clinically important difference of 30m compared to 25% in two-limb (p=0.02). 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 to two-limb (-1.75, p=0.01), but training volume was not significantly increased (+23%, p=0.179). Quadriceps muscle citrate synthase activity (+19%, p=0.03), hydroxyacyl-coenzyme A dehydrogenase protein levels (+32%, p Interpretation Single-limb LLHR-RT did not further increase mean 6MWD compared to two-limb LLHR-RT but it reduced exertional dyspnea and enabled more people reaching 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.