OBJECTIVE: To assess the relationship between the mean physical activity level (PAL) and the time spent on activities of three different intensity levels in an elderly population. Data was compared with previously obtained data from a group of younger adults. SUBJECTS: Fourteen elderly women and 14 elderly men (61±4 y; 27±5 kg/m2; 33±7% body fat), and 14 young women and 16 young men (27±5 y, 24±2 kg/m2). MEASUREMENTS: PAL was determined as average daily metabolic rate (ADMR) combined with a measurement of basal metabolic rate (BMR): PAL=ADMR/BMR. ADMR was measured with the doubly labeled water method. BMR was measured with a ventilated hood system. Time spent on activity and activity intensity was measured by using a tri-axial accelerometer (7´2´0.8 cm, 30 g) over a 2 week interval. RESULTS: Mean PAL was 1.65±0.14. PAL was inversely related to the percentage of time spent on low-intensity activity (lying, sitting and standing), r=-0.43; P<0.05. Older subjects spent significantly more time at these activities than 20 to 35-y-old subjects (82±7% vs 65±7%; P<0.0001). A significant relation was not observed between PAL and the percentage of time spent on moderate (walking) or high (household activities, exercise and sports) intensity activity, or activity monitoring time (14.4±1.2 h/day). CONCLUSION: In the elderly, spending relatively more time on low-intensity activities affects the mean PAL negatively. To obtain a higher PAL does not necessarily imply high-intensity activities like sports. International Journal of Obesity (2001) 25, 935-939 | 
