The purpose of the present study was to examine whether the level of oxygen uptake (Vo2) at the onset of decrementload exercise (DLE) is lower than that at the onset of constant-load exercise (CLE), since power output, which is the target of Vo2 response, is decreased in DLE. CLE and DLE were performed under the conditions of moderate and heavy exercise intensities. Before and after these main exercises, previous exercise and post exercise were performed at 20 watts. DEL was started at the same power output as that for CLE and power output was decreased at a rate of 15 watts per min. Vo2 in moderate CLE increased at a fast rate and showed a steady state, while Vo2 in moderate DLE increased and decreased linearly. Vo2 at the increasing phase in DLE was at the same level as that in moderate CLE. Vo2 immediately after moderate DLE was higher than that in the previous exercise by 98±77.5 ml/min. Vo2 in heavy CLE increased rapidly at first and then slowly increased, while Vo2 in heavy DLE increased rapidly, showing a temporal convexity change, and decreased linearly. Vo2 at the increasing phase of heavy DLE was the same level as that in heavy CLE. Vo2 immediately after heavy DLE was significantly higher than that in the previous exercise by 156±131.8 ml/min. Thus, despite the different modes of exercise, Vo2 at the increasing phase in DLE was at the same level as that in CLE due to the effect of the oxygen debt expressed by the higher level of Vo2 at the end of DLE than that in the previous exercise.

Department of Exercise Physiology Graduate School of Education Hokkaido University Kita ku Sapporo

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