Using the RT3 accelerometer to measure everyday activity in functionally impaired older people.

BACKGROUND AND AIMS: Triaxial accelerometry may provide a simple measure of physical activity in older people, but the effect of different walking aids and accelerometer placements on measurement is not known. This study aimed to examine the effect of accelerometer placement, use of walking aids, and different types of physical activity on Stay- Healthy RT3 triaxial accelerometer readings in older people.
METHODS: Twenty subjects aged over 65 years and five younger volunteers were recruited from Medicine for the Elderly services. Subjects performed six minutes each of standardized standing activity, sitting activity, sitting at rest, walking, and stair climbing. Counts generated from RT3 accelerometers worn anteriorly over both hips were recorded in subjects using different walking aids during these standardized activities.
RESULTS: There were significant differences between counts generated by the left and right hip positions. The intraclass correlation coefficient of RT3 counts between left and right hip positions was 0.48, 0.39 and 0.99 for sedentary tasks (standing, sitting and rest), stair and walking tasks respectively. Counts ranged between 250-3000 min-1 during the walking task. Counts were proportional to the distance walked. Resting, sitting or standing all generated counts below 250 min-1, but there was no clear demarcation between these activities. The use of different walking aids did not affect the counts generated for any activity.
CONCLUSIONS: Walking can be distinguished from other activities by upper and lower cutoffs. The RT3 accelerometer should be used on the same side of the body. Different walking aids do not appear to affect RT3 counts in older people.