DAILY PHYSICAL-ACTIVITY ASSESSMENT - COMPARISON BETWEEN MOVEMENT REGISTRATION AND DOUBLY LABELED WATER

The use of movement registration for daily physical activity assessmen t was evaluated during a 7-day period in 30 free-living subjects. Body movement was registered with a Tracmor motion sensor consisting of a triaxial accelerometer and a data unit for on-line processing of accel erometer output over 1-min intervals. Average Tracmor output was corre lated against four different energy estimates: 1) average daily metabo lic rate (ADMR), determined with doubly labeled water; 2) ADMR-sleepin g metabolic rate (SMR; determined in a respiration chamber); 3)(ADMR-S MR) per kilogram of body mass; and 4) the overall physical activity le vel (PAL=ADMR/SMR). The highest correlation was found for the relation ship between Tracmor output and PAL (r=0.58). After correction for Tra cmor values arising from vibrations produced by transportation means, this correlation was improved to 0.73. There was no difference between Tracmor output and PAL in discriminating between overall activity lev els with ''low'' (PAL <1.60), ''moderate'' (1.60 less than or equal to PAL less than or equal to 1.85), and ''high'' (PAL >1.85) intensity. It is concluded that the Tracmor can be used in free-living subjects t o distinguish among interindividual as well as intraindividual levels of daily physical activity.