Day-to-day variability of physical activity of older adults living in the community.

The purpose of the study was to investigate whether a 24-hr recording period is sufficient to describe physical activity (PA) of 1 week for intraindividual comparison in older adults. Furthermore, the authors analyzed whether physical performance can be used as a surrogate marker of PA. PA was captured on 7 consecutive days by a body-fixed sensor in 44 community-dwelling older adults (80.75 +/- 4.05 yr). Mean times of walking and of "time on feet" of the group were 10.2 hr (+/- 3.5) and 35.1 hr (+/- 9.43), respectively. Intraindividual variabilities of walking and of time on feet were 31.9% +/- 10.79% and 19.4% +/- 8.76%, respectively. Accumulated time of variables of PA showed no differences between weekdays, with variabilities of 3.8% and 1.8% for walking and time on feet, respectively. Association between Short Physical Performance Battery and PA was limited (walking r = .397, time on feet r = .41).