Background:A novel actigraphy method, the proportional integral mode, was used for monitoring metabolic rate and energy expenditure during different levels of exercise intensity.Material/Methods: 13 young (24±3yrs) male subjects, clothed in T-shirts, shorts and athletic shoes, ran/walked for 30 min on a level treadmill at different speeds (3, 5, 2, 6, 4, and 7 mph), 5 min at each speed. The following variables were continuously measured: Actigraphy (PCD, USA) data at three different modes (proportional integral mode, zero crossing, and time above threshold) from the wrist; oxygen consumption (Sensor Medics, USA), and heart rate (Polar, Finland).Results: Analysis of the measured data revealed with low correlation between oxygen consumption and zero crossing or time above threshold (R=0.364 and 0.384, respectively), but with high correlation between oxygen consumption and proportional integral mode (R=0.843).Conclusions: The proportional integral mode, which is unlike the other modes, followed the oxygen consumption and the heart rate curves, showing a potential unique method to predict oxygen consumption and energy expenditure.

Keywords: Calorimetry, Indirect - methods, Miniaturization - instrumentation, Walking - psychology, Calorimetry, Indirect - methods, Energy Metabolism - physiology, Exercise Test - methods, Miniaturization - instrumentation, Oxygen Consumption - physiology, Running - physiology, Walking - psychology