Chronic obstructive lung disease (COPD) is associated with impaired muscle functions in addition to the impaired cardiopulmonary capacity inherent to the disease.The purpose of this study was to compare muscular performance between COPD subjects (COPD, n = 11, GOLD grade II/III; FEV 1 = 53 ± 14% predicted; 61 ± 7 years) and healthy controls (HC, n = 12, 66 ± 8 years) in three resistance exercises with different complexity: (a) one-legged knee extension (1KE), and (b) one-and (c) twolegged leg press (1LP and 2LP, respectively). For each exercise, muscular performance was defined as repetitions to exhaustion at 60% of one-repetition maximum or overall exercise volume, calculated as the sum of three exercise sets. In HC, muscular performance increased progressively with increasing physiological complexity: 1KE < 1LP < 2LP. Using 1KE as reference value, muscular performance increased by 1.9 (repetitions) or 4.6-fold (volume) in 1LP and 3.1 or 7.1-fold in 2LP. In COPD, similar increases occurred going from 1KE to 1LP (1.9 or 4.4-fold change), but not from 1LP to 2LP, where no further increase occurred. In conclusion, in COPD, performance is impaired in exercises involving larger amounts of muscle mass (>1LP), advocating utilization of one-legged resistance protocols for rehabilitation purposes. K E Y W O R D Scardiorespiratory capacity, chronic obstructive lung disease, muscular performance, resistance training, strength training, unilateral training How to cite this article: Mølmen KS, Evensen Thy E, Thallaug Dalane S, Ellefsen S, Falch GS. Muscular performance decreases with increasing complexity of resistance exercises in subjects with chronic obstructive pulmonary disease. Transl Sports Med.