Evaluation of a body-worn sensor system to measure physical activity in older people with impaired function.

Background: There is limited information on reliable and valid measures of physical activity in older people with impaired function.

Objective: This study was conducted to compare the accuracy of single-axis accelerometers in recognizing postures and transitions and step counting with the accuracy of video recordings in people with stroke (n=14), older inpatients (n=14), people with hip fracture (n=8), and a reference group of 10 adults who were healthy.

Design: This was a cross-sectional study, evaluating the concurrent validity of small body-worn accelerometers against video observations as the criterion measure.