The purpose of this study was to investigate whether individual leg cycling could produce higher whole body peak oxygen uptake (VO(2peak)) than two legs cycling during aerobic high intensity interval training in chronic obstructive pulmonary disease (COPD) patients. Nineteen patients trained in 24 supervised cycling sessions either by one leg training (OLT) (n = 12) or by two legs training (TLT) (n = 7) at 4 x 4 min intervals at 85-95% of peak heart rate. Whole body VO(2peak) and peak work rate increased significantly by 12 and 23% in the OLT, and by 6 and 12% in the TLT from pre- to post-training, respectively, and were significantly greater in the OLT than the TLT (P < 0.05). The present study demonstrates that one leg aerobic high intensity interval cycling is superior to two legs in increasing whole body VO(2peak), indicating a muscle rather than a cardiovascular limitation to VO(2peak) in these COPD patients.