Broad scope of a newly developed actometer in chronobiology, particularly chronocardiology.

The scope and the details of a newly developed actometer were introduced. We are able to select a desired threshold of gravity(g)-forces between 0.01g and 0.50g and to simultaneously monitor 3 kinds of activity along with an averaged g-force every minute. As a routine study, we monitored at settings of 0.01g, 0.05g and 0.20g and averaged on one channel. Part of the time, physical activity was monitored together with ambulatorily monitored blood pressure (BP) and the ECG, or at least heart rate (HR). Physical activity showed a circasemiseptan and circaseptan periodicity as well as the circadian component, especially in subjects with an irregular sleep-wakefulness life style. On the average, physical activity was greater on a working day than on a holiday. Everyday physical activity reflects in part the ability to exercise, and it is expected that this actometer can contribute or provide an objective individualized quality-of-life index. The effect of physical activity on circadian profiles of BP, HR and HR variability is also examined. We observed that BP started to increase several hours before getting up. This fact likely shows that there is an endogenous circadian rhythm in BP, independently of the sleep-wakefulness cycle. Lastly, we investigated the relationship between physical activity and HR in patients permanently paced; we confirmed that the DDDR pacing mode was more physiological than the VVI or VVIR mode. This newly developed actometer will bring about further progress in chronobiology.