Maximal accumulated O2 deficit in running and cycling

The purpose of this study was to compare values for maximal accumulated O2 deficit measured in running and cycling. Nine university students performed five fatiguing constant-velocity treadmill tests and five fatiguing constant-power cycle ergometer tests at intensities within the severe domain. O2 deficit was determined making the traditional assumptions that (1) the O2 demand increases linearly with the exercise intensity and (2) the O2 demand is constant from the onset of exercise if the intensity is kept constant (Medbø, 1996). VO2max was 11% higher in running than in cycling. In contrast, O2 deficit was approximately 50% higher in cycling than treadmill running. Inspection of the data suggested that the O2 demand may have been underestimated, especially in the treadmill tests. It was concluded that assumptions associated with measuring maximal accumulated O2 deficit in running must be revisited.