作業負担指標としての心拍数の自己相関関数とパワースペクトル

Abstract

臥位, 坐位および自転車エルゴメータによる3つの異なった負荷下における被験者の心拍数を連続的に測定し, それ等をランダム変動をする時系列データとみなして自己相関関数およびパワースペクトルを計算し, 各場合の心拍数の時間的変動特性を検討した。その結果 : 臥位では深呼吸のリズムにほぼ対応する周期で心拍数は変動したが, 坐位では周期性が不明瞭になりいくつかの周期成分が混在した変動を示した。一方, 負荷下の心拍数は, 軽い負荷ではエルゴメータのペタル回転速度に関連したリズムで心拍数が変動する場合が認められたが, 負荷が大きくなるとこの対応関係は失われランダム性が増加した。これ等心拍数変動の傾向は, 被験者の測定時における心的状態により異なる場合も認あられた。

ECGs for two subjects were measured with an FM teremetry system during lying, sitting and riding a bicycle ergometer at three different loads. The heart rates which calculated from the ECGs at every two seconds interpreted as the random and digital data, and the auto-correlation functions and the power spectra of them were computed in order to study the dynamic characteristics of the heart rate changes. The results may be summerized as follows. 1) The periods of the heart rate changes for lying nearly corresponded to the ones of the deep breathing of each subject. On the other hand, the periods for sitting consisted of several periodic elements and were apt to be in disorder, because that to keep the posture of sitting was more difficult than of lying. 2) The heart rate for cycling changed with the periods related to the tempo of the pedaling of the bicycle ergometer when the work load was lighter (load 1, 2), but the periodicity was lost and became to be dominated by randomness when the work load was heavier (load 3). 3) It is also true that the tendencies of the heart rate changes mentioned above were affected by an individual difference and the mental conditions of subjects during the measurement of ECG.