QUANTIFICATION OF PHYSICAL ACTIVITIES BY MEANS OF AMBULATORY ACCELEROMETRY - A VALIDATION-STUDY

The objective of the study was to assess the validity of an activity m onitor (AM) within a psychophysiological study. The AIM was based on f our body-fixed accelerometers and discriminated postures, transitions, and dynamic activities. Three subjects participated in each of two 4- hr sessions. During each session, consisting of two protocols, ambulat ory accelerometer and heart rate measurements were made. The output of the AM was compared with simultaneously recorded video tapes. An over all agreement between AM and video of 88 and 96% was found. The number of transitions and dynamic periods, and the duration of activities we re well determined. Posture-related heart rate changes were demonstrat ed. A three-sensor configuration hardly influenced the validity scores . The AM appeared to be a valid instrument to quantify aspects of phys ical activity, and offers new possibilities for ambulatory psychophysi ological research.