A portable heart rates (HR) memory system is very convenient for the field study. Such kinds of equipments are now put on the market. They are, however, highly expensive or of capacity of short recording time. Therefore, the authors participated in making a portable and low-priced equipment for recording a day\u27s HR on an experimental basis. This kind of portable equipment has to record HR with a high degree of accuracy however strenuous the exercise may be. The authors forced so hard exercise on the adult male subjects that HR reached to about 200 beats per minute. Then, they led HR from the subject with the above-mentioned equipment and with the polygraph (i.e. direct method) simultaneously. As a result, the discrepancy of HR between two methods was so small as to be negligible for practical use. It has been supposed that this equipment offers an effective means to the field work of health science
