FREE-LIVING ENERGY-EXPENDITURE OF ADULT MEN ASSESSED BY CONTINUOUS HEART-RATE MONITORING AND DOUBLY-LABELED WATER

Free-living energy expenditure was estimated by doubly-labelled water (DLW) and continuous heart-rate (HR) monitoring over nine consecutive days in nine healthy men with sedentary occupations but different leve ls of leisure-time physical activity. Individual calibrations of the H R-energy expenditure (EE) relationship were obtained for each subject using 30 min average values of HR and EE obtained during 24 h whole-bo dy calorimetry with a defined exercise protocol, and additional data p oints for individual leisure activities measured with an Oxylog portab le O-2 consumption meter. The HR data were processed to remove spuriou s values and insert missing data before the calculation of EE from sec ond-order polynomial equations relating EE to HR. After data processin g, the HR-derived EE for this group of subjects was on average 0.8 (SE M 0.6) MJ/d, or 6.0 (SEM 4.2)% higher than that estimated by DLW. The diary-respirometer method, used over the same 9 d, gave values which w ere 1.9 (SEM 0.7) MJ/d, or -12.1 (SEM 4.0)% lower than the DLW method. The results suggest that HR monitoring can provide a better estimate of 24 h EE of groups than the diary-respirometer method, but show that both methods can introduce errors of 20% or more in individuals.