Development of wristwatch-type heart rate recorder with acceleration-pickup sensor and its application.

We have developed a wristwatch-type heart rate (HR) recorder (WT-HR tachometer) with an acceleration-pickup sensor, which can record HR and body activity (ACT) minute by minute for a long time (> 120 h). To study its application, we compared these measurements with 24-h blood pressure (BP) and HR variability, sympathovagal balance, and resting energy expenditure (REE). The WT-HR tachometer incorporates a Seiko-blue sensor to measure HR at the wrist and an acceleration-pickup sensor to measure body ACT every 4 sec. Fifty healthy university students underwent measurement of HR and ACT by the WT-HR tachometer for 24 h. Then we calculated the minimum HR and mean HR during waking time and derived deltaHR. On the same day, 24-hr BP and LF/HF (low frequency component/high frequency component of ECG-RR interval power spectrum) were measured with a multibiomedical recorder, and REE was measured with a portable calorimeter. The WT-HR tachometer accurately measured HR, compared with the measurements by Holter-ECG. There was a significant correlation between deltaHR and deltaSBP. There also was a significant correlation between deltaHR and deltaLF/HF, (waking time = waking time without body movement) and a significant correlation between HR and REE. These results suggest that ACT and deltaHR are useful for evaluating mental and physical activity of daily life. The WH-HR tachometer will be useful for assessment of mental and physical activity in daily life.