Evaluating Walking Intensity with Hip-Worn Accelerometers in Elders.

Abstract

Accelerometer activity counts are used to objectively categorize physical activity levels. We examined the association between accelerometer activity counts and metabolic effort in older adults. Forty-five older adults (76.3 ± 5.1 yr) completed a 400-m walk at both a usual and a rapid pace. A portable metabolic unit measured pulmonary gas exchange, whereas a hip-worn accelerometer measured activity counts. Participants were categorized as either a "slow walker" or a "fast walker" based on the threshold of 1.0 m·s during usual-pace walking. Activity counts during rapid (r = 0.62, P < 0.01) but not usual-pace (r = 0.24, P = 0.11) walking were significantly associated with METs. Slow walkers attained only half the activity counts of fast walkers during each walk condition (P < 0.01), while at the same time achieving between 82% and 90% of their MET level. Accelerometers may misclassify the activity level of functionally impaired older adults with slow walking speed.