Presently, heart rate is used to estimate physiological load on the body during physical activity. However, ECG or specialized apparatus for measuring heart rate entail high cost, therefore, they are impractical for use with large groups of people.
　In order to measure heart rate simultaneously in a large group of children, we devised an inexpensive portable type of ECG recording apparatus which was made by reconstruction audio micro cassette tape recorder (cost: 12000 yen). That is, thought P.F.M. (Pulse Frequency Modulation) we input the ECG signal(which is an analog signal) by way of a circuit to convert it into a pulse signal, which was then fed into a small tape recorder.
　In this experiment, we devised our own ECG recording apparatus, recorded the pulse rate of 10 first-graders, 10 third-graders, and 10 fourth-graders during physical education class, and made our measurements according to ECG R-waves.
　The portable design of the recording devices allowed sufficient application. In al grades, heart rate in physical education class proved to be high, (131.9 beats/min-146.7 beats/min) during main teaching material, and low (111.3 beats/min-124.0 beats/min) during the teacher's explanations, or reflections upon one's own performance.
　Judging from the time required for warming up, main teaching material, and supplementary activities, the objective of this study (physical education class) proved to be significant in improving physical education.

DESCENTE SPORTS SCIENCE Vol.5/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE