Purification of masked temperature data from humans: Some preliminary observations on a comparison of the use of an activity diary, wrist actimetry, and heart rate monitoring

Fourteen ambulatory subjects, varying in their amount of habitual physical activity, were studied for 24h during a total of 25 "typical" days. Rectal temperature was recorded every 6 minutes, an activity diary was filled in e very half hour, and wrist activity and heart rate were monitored every minu te. Actimetry and heart rate data generally showed close parallelism with e ach other and with the masking effects on body temperature. Psychological s tressors such as public speaking produced a greater effect on heart rate an d body temperature than on wrist movement, while typing produced high value s for wrist movement, but affected heart rate and temperature much less. Wh en data for the circadian rhythm of body temperature were purified, the dia ry, actimetry, and measurement of heart rate were all useful in reducing ma sking effects, but the present evidence indicates that heart rate can be mo re successful than actimetry-as judged by the closeness of the purified dat a to a sinusoid. This superiority of heart rate monitoring over wrist activ ity as a method of purification might be because core temperature can be in creased by stressor-induced thermogenesis, as well as by physical activity, and because wrist movement can, with some activities, give an inaccurate e stimate of the factors that contribute to whole-body thermogenesis.