To make the program of training, such as running speed, maximum oxygen intake is very useful. The purpose of this research is to investigate better method of measuring oxygen intake, not only for large value but also for subjecive feeling. In this reseach, we corn pared two different methods.
　The first method is the progressive protocol, which has been used for many years. In every two minutes, treadmill speed increased by 20 m/min and kept same speed for two minutes. The second is self-selected protocol. The subjects were able to select running speed by themselves using remote control switch while running on the treadmill. All through these protocols, the treadmill was fixed at 5 % uphill, and the expired gas was analyzed breath by breath, then calculated for one minute in both protocols.
　The subjects were healthy male students belonged to the track and fields club and average record of 5000 m was 14 minutes and 55 seconds.
　The maximum oxygen intake measured by the self-selected protocol was 75.9 ml/kg/min and was 73.5 ml/kg/min taken by the progressive protocol. In case of the self-selected protocol, the maximum oxygen intake appeared earlier than in the progressive protocol. And the coefficient of variation of oxygen intake, analyzed breath by breath, was smaller in case of the self-selected protocol than in the progressive way during the period of maximum oxygen intake for one minute. The fact of steady state about oxygen intake, which could be supposed by small coefficient of variation, seems optimum running pace for the runner.
　Running speed was decided from all the conditions, running road and climate of the season and physical responses such as cardiovascular system and muscles. The breath by breath analyzing system is not only easy but also beneficial for subjects.

DESCENTE SPORTS SCIENCE Vol.14/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE