Abstract
Heart rate (HR) is affected by physical activity (PA) and mental conditions during awake and sleep, both of which produce a circadian rhythm of the HR. Numerous studies reported relationships between HR and PA. However, little is known about the method to evaluate mental stress based on the HR-PA data in free-moving humans. The aims of the present study were to examine relationships between HR and PA and to find a clue to assess mental stress out of the relations. Subjects were a healthy adult woman and 5 men. Most of them were hospital workers. Continuous recordings of HR and PA were performed for 24 hours or more by using a portable monitor (Active Tracer AC-301, GMS Inc., Japan). PA was assessed by the number of counts beyond an acceleration of 0.02G. Physical behaviors and mental status were briefly described on sheets or recorded by an IC-voice recorder. In most cases during sleeping and awake, HR had a significant correlation with PA due to turning over in bed. In the subjects who did not feel any remarkable stress during daytime including working hours, logarithm plots of HR vs. PA exhibited a statistically significant linear correlation. However, in a subject who experienced mental stress during his work, frequent increases in HR with low levels of PA produced a prominent variability in the logarithm plot of HR-PA. HR-PA plot may be avaiable for the evaluation of such non-physical stress as mental one. [Jpn J Physiol 54 Suppl:S94 (2004)]
