Pedometer Accuracy And Intensity Distribution Of Physical Activity In Younger Versus Older Subjects

Abstract

PURPOSE The purpose of this investigation was to examine the pedometer accuracy in younger and older adults. METHODS Seventeen younger individuals (YI) and 28 elderly individuals wore a pedometer with a one-axial accelerometer (Life-Corder, LC) and an electrical pedometer (EC-200, YM) simultaneously for seven days on the left waist. The number of step was assessed by the two pedometers, and LC assessed the time spent in light, moderate and vigorous intensity physical activity. Elderly subjects were divided in one of two groups (active elderly: AE and inactive elderly: IE) according to the number of steps (=7500 steps/day). RESULTS Although AE took the higher number of steps and spent longer time in light intensity physical activity compared with YI (10736+/-3465 vs. 8866+/-1940 steps/day and 64+/-22 vs. 48+/-10 min/day, p<0.05), the time spent in moderate intensity physical activity did not differ significantly between two groups (32+/-18 vs. 35+/-12 min/day). In contrast, IE spent the same amount of time in light intensity physical activity (42+/-9 min/day) compared with YI (48+/-10 min/day), whereas the number of steps and the time spent in moderate intensity physical activity differed significantly (5402+/-1071 vs. 8866+/-1940 steps/day and 15+/-7 vs. 35+/-12 min/day, p<0.01). Furthermore, in IE, the relative time spent in light intensity physical activity (77+/-12%) was significantly longer than other two groups (p<0.01). The number of steps assessed by LC was significantly higher than the number of steps assessed by YM in overall subjects (8607+/-3197 steps/day vs. 7195+/-3144 steps/day, p<0.01), yet there was a strong relationship between the two measurements (r=0.962, p<0.01). The magnitude of the difference was significantly correlated with the relative time spent in light intensity (r=0.523, p<0.01) as well as the time spent in moderate intensity physical activity (r=−0.563, p<0.01). Consequently, in IE, the magnitude of difference (29+/-14%) was greater than in the other two groups (p<0.01), and the correlation between the two measurements was only modest (r=0.689, p<0.001). CONCLUSIONS The pedometer accuracy may decrease in elderly individuals due to greater length of time spent in light intensity physical activity and to the minimal time spent in moderate intensity physical activity. Therefore, elderly individuals should be encouraged to improve/maintain the daily physical activity levels based on the intensity of physical activity rather than on the number of steps.