The purpose of this study is to investigate extent of strain during several kinds of physical exercise in mentally retarded males. Educable and trainable mentally retarded high-school students (N=11) were examined for heart rate response to several kinds of exercise.
　Pulse-watch (MRC-1200) was used for measurement of heart rate (HR). HR during foot-baseball, indoor-hockey, 2km-running, circuit-training and dance-activity were observed.
　Results were as follows:
　1. The exercise which had the highest HR was 2 km running. It was followed by circuit-training, dancing, foot-baseball and indoor-hockey.
　2. 2 km running is the most effective sport for improvement of endurance ability.
　3. For obtaining endurance ability by ball-game, it seems necessary to give consideration to playing area and number of players.
　4. Measurement of HR is a good way to eraluate extent of strain in MR students who have difficulty in expressing their subjective declaration.

DESCENTE SPORTS SCIENCE Vol.13/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE