Introduction: Accurate yet inexpensive methods for measuring free-living energy expenditure (EE) are
much needed. The aim of this study was to determine the feasibility of heart-rate monitoring method
(HRM) in measuring EE as compared to the established activity diary (AD) method. Methodology:
Minute-by-minute HRM and an activity diary (AD) were used simultaneously in 34 young adults (18
females, 16 males; mean age 21.5 ± 1.5 years). Estimates of the EE from HRM were based on individual
calibration using the Flex-HR procedure while EE from AD were calculated using both individually
measured and published energy cost of various activities. Total daily energy expenditure (TDEE) and its
components (EE during sleep, during rest and during physical activity) were compared using Student
paired-t tests. Results: TDEE from HRM method averaged 8.17 ± 2.00 MJ/day compared to 8.50 ±
1.28 MJ/day from AD method. Although large intra-individual differences were found (ranging from
-36.9% to 47.4%), there was no significant difference between the two methods (mean difference -3.6 ± 19.4%). The limits of agreement (mean ± 2SD) were -3.77 and 3.11 MJ/day. There were no significant
differences for any of the TDEE components between the two methods, except for EE during sleep
(p