Assessment Of Energy Expenditure During Physical Activity Using Synchronised Accelerometry And Heart Rate

Abstract

PURPOSE To determine the accuracy of estimates of energy expenditure using branched equations for synchronised accelerometry and heart rate (AHR) during a 2 h period of structured activity reflecting low to moderate intensity physical activities. METHODS 10 male and 10 female subjects (mean age 26 ± 5 years, height 173 ± 7 cm and body mass 72 ± 11 kg) performed a 2 h laboratory-based protocol simulating six low to moderate intensity physical activities. Each activity lasted 8 min and was interspersed with 8 min supine rest. Activities included treadmill walking at 4.8 km.h−1, sweeping, digging in sand, simulated watering of plants, treadmill walking at 5.6 km.h−1 whilst carrying 4% body mass in each hand and folding and stacking sheets. These activities were chosen as they range from low to moderate intensity physical activity according to assigned values (2–5 metabolic equivalents). These activities include movements where the use of accelerometry and heart rate may be most limited and therefore provide data that may represent a worst-case scenario. Energy expenditure was estimated throughout using indirect calorimetry (COSMED, Italy) and AHR (Cambridge Neurotechnology Ltd., UK). Established default equations for AHR were used to estimate energy expenditure and we also developed new calibration equations derived from both group and individual data. RESULTS Mean energy expenditure across all six physical activities determined using indirect calorimetry was 3.6 ± 0.3 kcal·min−1. The comparison between methods was conducted using ordinary least-products regression. The standard error of the estimate for the prediction of energy expenditure from AHR was 0.4 kcal·min−1 for default equations, new group equations and individual calibration equations during the period of observation. If this were extrapolated to a typical day where an individual was active for 16h, this would be equivalent to 384 kcal (this represents approximately 15% of total energy expenditure if energy expenditure was 2500 kcal.day−1). CONCLUSION These results demonstrate that AHR is a promising tool for the estimation of energy expenditure during low to moderate intensity physical activities. It appears that deriving new group equations or individual calibration equations may not be necessary.