Walking speed and placement position interactions in the accuracy of various newer pedometers
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Introduction: Pedometers are increasingly used as a self-monitoring aid for achieving and increasing daily physical activity. Older pedometers had varied levels of accuracy ranging from 0 to 45% difference and were needed to be positioned in a certain way (on the waist). Newer models can be placed anywhere on the body but its accuracy is unknown when they are placed at different bodily sites. Purpose: We determined the accuracy of various newer pedometers under controlled laboratory and free walking conditions. Method: A total of 40 subjects (20 male and 20 female) varying widely in age (18-61 years) and BMI (18-38 kg/m²) were studied. The pedometers, including Omron HJ-320, Omron HJ-324U, Lifesource XI-25, Fitbit Ultra, and Virgin Health Miles, were placed at waist, at chest, in a pocket, and on an armband. The number of steps recorded with the pedometers was compared against those counted with a hand tally counter while the subjects walked on the treadmill at 54, 80, 107, 134, and 161 m/min and on paved ground outside at a self-selected pace. Results: With the exception of one, all the pedometers were accurate (within ±5% of the criterion measure) at moderate walking speeds (80 and 107 m/min). The results were similar no matter where the pedometers were placed on the body and where the walking was performed. There were general tendencies for the accuracy to decrease at slower and faster walking speeds in most pedometers. The mean difference scores increased particularly when the pedometers were placed in the pockets or in the purse. Conclusions: Most of the pedometers examined were accurate when they were placed at waist, chest, and armband no matter what walking speed or what terrain they exercised. But some pedometers did not register accuracy when they were put in the pocket or in the purse particularly at a slow and fast walking speed.