THE AMBULATORY MEASUREMENT OF POSTURE, THIGH ACCELERATION, AND MUSCLETENSION AND THEIR RELATIONSHIP TO HEART-RATE

We compared the relative ability of continuous accelerometric, electro myographic (EMG), and hydrostatic posture measurements to discriminate tasks involving variations in motor activity and posture and to predi ct heart rate (HR) variability. EMG was a more sensitive measure than accelerometry in differentiating the tasks. However, accelerometry and EMG explained comparable amounts of HR variance. The hydrostatic post ure was a stable measure that clearly differentiated postures and expl ained a significant amount of HR variance but less than accelerometry or EMG. Accelerometric and EMG measures of motor activity used either alone or in combination with the hydrostatic posture are valuable in d iscriminating activities and in controlling for the effects of motor a ctivity and posture on HR during ambulatory measurement.