The purpose of the present study was to examine 1) whether O-2 uptake (VO2) oscillates during light exercise and 2) whether the oscillation is enhanced after impulse exercise. After resting for 1 min on a bicycle seat, subjects performed 5-min pre-exercise with 25 watts work load, 10-s impulse exercise with 200 watts work load and 15-min post exercise with 25 watts work load at 80 rpm. VO2 during pre-exercise significantly increased during impulse exercise and suddenly decreased and re-increased until 23 s after impulse exercise. In the cross correlation between heart rate (HR) and VO2 after impulse exercise, VO2 strongly correlated to HR with a time delay of -4s. Peak of power spectral density (PSD) in HR appeared at 0.0039 Hz and peak of PSD in VO2 appeared at 0.019 Hz. The peak of the cross power spectrum between VO2 and HR appeared at 0.0078 Hz. The results suggested that there is an oscillation in O2 uptake during light exercise that is associated with the oscillation in O2 consumption in active muscle. The oscillation is enhanced not only by change in O2 consumption but also by O2 content transported from active muscle to the lungs.