Purpose : Although sport climbing is a self-paced whole-body activity, speed varies with climbing style, and the effect of this on systemic and localized oxygen responses is not well understood. Therefore, the aim of the present study was to determine muscle and pulmonary oxygen responses during submaximal climbing at differing speeds of ascent. Methods : Thirty-two intermediate and advanced sport climbers completed three 4-minute-long ascents of the same route at 4, 6, and 9 m˙min −1 on a motorized climbing ergometer (treadwall) on separate laboratory visits. Gas analysis and near-infrared spectroscopy were used to determine systemic oxygen uptake ( ) and muscle oxygen saturation (StO 2 ) of the flexor digitorum profundus. Results : Increases in ascent speed of 1 m˙min −1 led to increases of by 2.4 mL˙kg −1 ˙min −1 (95% CI, 2.1 to 2.8 mL˙kg −1 ˙min −1 ) and decreases in StO 2 by −1.3% (95% CI, 1.9% to −0.7%). There was a significant interaction of climbing ability and speed for StO 2 ( P < .001, ). The results revealed that the decrease of StO 2 was present for intermediate but not advanced climbers. Conclusions : In this study, the results suggest that demand during climbing was largely determined by climbing speed; however, the ability level of the climber appeared to mitigate StO 2 at a cellular level. Coaches and instructors may prescribe climbing ascents with elevated speed to improve generalized cardiorespiratory fitness. To stimulate localized aerobic capacity, however, climbers should perhaps increase the intensity of training ascents through the manipulation of wall angle or reduction of hold size.