Simultaneous heart rate-motion sensor technique to estimate energy expenditure

Purpose: Heart rate (HR) and motion sensors represent promising tools for p hysical activity (PA) assessment, Lt.,, each prod ides an estimate of energ y expenditure (EE). Although each has inherent limitations. the simultaneou s use of HR and motion sensors may increase the accuracy of EE estimates. T he primary purpose of this study was to establish the accuracy of predictin g EE from the simultaneous HR-motion sensor technique. In addition, the acc uracy of EE estimated by the simultaneous HR-motion sen. or technique was c ompared to that of HR and motion sensors used independently. Methods: Thirt y participants (16 men: age. 33.1 +/- 12.2 yr: BMI, 20.1 +/- 0.7 kg.m (2): and 14 women: age, 31.9 +/- 13.1 yr: BMI. 27.2 +/- 1.1 kg.m(-2) (mean +/- S D)) performed arni and leg work in the laboratory for the purpose of develo ping individualized HR-VO2 regression equations. Participants then performe d physical tasks in a field setting for 15 min each. CSA accelerometers pla ced on the arm and leg were to discriminate between upper and lower body mo vement, and HR was then used to predict EE (METs) from the corresponding ar m or leg, laboratory regression equation. A hip-mounted CSA accelerometer a nd Yamax pedometer were also used to predict EE. Predicted values (METs) we re compared to measured values (METs). obtained via a portable metabolic me asurement system (Cosmed K4b(2)). Results: The Yamax pedometer and the CSA accelerometer on the hip significantly underestimated the energy cost of se lected physical activities. whereas HR alone significantly overestimated th e energy cost of selected physical activities. The simultaneous HR-motion s ensor technique showed the strongest relationship with (V)over dotO(2) (R-2 = 0.81) and did not significantly over- or underpredict the energy cost (P = 0.341). Conclusion: The simultaneous HR-motion sensor technique is a goo d predictor of EE during selected lifestyle activities. and allows research ers to more accurately quantify free-living PA.