DEOXYGENATON DURING INTENSE CYCLING IMMEDIATELY AFTER PROLONGED CYCLING

378 The capacity to spurt in the last lap seems one of the most important factors to win middle and long distance races. The purpose of this study was to characterize deoxygenation of the selected muscle during high intense exercise performed immediately after prolonged lower intensity of exercise. Six male subjects cycled at 300 watt for 3 min immediately after 30min-cycling at 50 watt (50-300W trial) and 150 watt (150-300W trial). Deoxygenated hemoglobin and/or myoglobin (deoxy-Hb/Mb) and total amount of deoxygenated and oxygenated Hb/Mb (total-Hb/Mb) of the vastus lateralis muscle was measured with near infrared spectroscopy. The relative changes in oxy-Hb/Mb and total-Hb/Mb were estimated by regarding values in resting condition as 0. Oxygen uptake was increased at 30 to 33min for both trials (13.5 to 45.05ml·kg-1·min-1 for 50-300W trial, 29.4 to 46.5ml·kg-1·min-1 for 150-300W trial). The deoxy-Hb/Mb was also increased for both trials (0.01 to 0.81 for 50W trial, 0.45 to 0.78 for 150W trial). The total-Hb/Mb was increased for 50-300W trial(0.56 to 0.86) and sustained for 150-300W trial (0.78 to 0.79). Delta oxygen uptake, delta deoxy-Hb/Mb and delta total-Hb/Mb between 30 and 31 min for 50W trial were significantly larger than for 150W trial. Delta oxygen uptake and delta deoxy-Hb/Mb between 32 and 33min for 50-300W trial were not significantly different from those for 150-300W trial. Delta total-Hb/Mb for 50-300W trial, however, was significantly larger than for 150-300W trial. These results suggested that increased O2 extraction might contribute to the increment of oxygen uptake in a transition from low to high intensity of exercise. To what extent, the increased blood flow contributed remains unresolved in each trial.