Validation of the physical activity index (PAI) as a measure of total activity load and total kilocalorie expenditure during submaximal treadmill walking

摘要

PURPOSE: The primary purposes of this investigation were to examine the validity of the Physical Activity Index (PAI) as, (a) a measure of total activity load (intensity of exercise x volume of exercise) and (b) as an estimate of total kilocalorie (kcal) expenditure during submaximal treadmill walking. A secondary purpose was to compare estimated kcal expenditure determined by the PAI prediction model to the estimated kcal expenditure determined by the SenseWear Pro Armband™. METHODS: Thirty-two recreationally active females (20.36 ± 1.27 years) participated in this study. Subjects participated in three counterbalanced submaximal walking bouts: low intensity (4.02 km⋅hr⁻¹, 0% grade), moderate intensity (5.63 km⋅hr⁻¹, 2.5% grade), and high intensity (7.24 km⋅hr⁻¹, 5% grade). Each bout was separated by five min of rest. During each of the three exercise bouts, oxygen consumption (VO₂), rating of perceived exertion (RPE), pedometer step count, and kcal expenditure were measured. The PAI was calculated as the product of RPE and pedometer step count for each of the three, 10 minute bouts of treadmill walking. RESULTS: Concurrent validation of the PAI was established using VO₂ and heart rate (HR) as the criterion variables. Multiple regression analyses revealed a strong, positive relation between PAI score and VO₂ (r = 0.92) and HR (r = 0.84). Data were then used to develop a statistical model to estimate kcal expenditure using the PAI score as the predictor variable. Walking kcal expenditure predicted by Model III was highly correlated with measured kcal expenditure (r = 0.85). Similarly, kcal expenditure estimated by the SenseWear Pro Armband™ evidenced a strong, positive correlation with measured kcal expenditure (r = 0.83) when calculated across the three walking intensities. CONCLUSION: The development of a PAI using RPE and pedometer step count to estimate kcal expenditure may have significant public health implications. The PAI was found to be more accurate then the Armband method of estimating kcal expenditure and is a simple, unobtrusive and inexpensive tool which may be used to assess kcal expenditure in public health, clinical, and/or rehabilitation settings.