A simple method of measuring total daily energy expenditure and physical activity level from the heart rate in adult men

Objective: To evaluate a simple method that uses only a heart rate monitor to predict total energy expenditure ( TEE) and physical activity level ( PAL) from 24 h heart rate (HR) measurements. Design: The simple method involved the determination of the physical activity ratio ( PAR) from corresponding heart rate ratios (HRR) ( ratio of observed to resting HR), from an individualized calibration curve relating activities with known PAR to the HRR. Several curve fits were evaluated for this curve. The PAL was calculated from minute to minute PAR. The TEE was computed as the product of the PAL and the predicted basal metabolic rate (BMR). The accuracy of the simple method was assessed by within-subject comparisons of the simple method versus the oxygen consumption - HR method and a time and motion study. Setting: Bangalore City, India. Subjects: In all, 17 healthy male subjects between 18 and 44 years were recruited for the study. Interventions: None. Results: The simple method correlated well with both the reference methods when using a calibration curve that involved the fitting of two straight lines at low and high PAR activities, respectively, to the PAR and HRR data. The mean error in TEE, as a product of BMR and PAL, was about 1%, but with limits of agreement between the methods that were about 20% of the TEE. However, the low mean error could have been due to a canceling of errors in the determination of BMR and PAL. Conclusions: The simple method is a relatively cheap, useful technique for evaluating TEE and PAL in resource-poor situations. It may particularly be of use in epidemiological investigations where population estimates of TEE and PAL are required.