Energy expenditure by heart rate in children: an evaluation of calibration techniques.
OBJECTIVE
To evaluate the impact of applying seven calibration equations (CE) in the estimation of free-living total energy expenditure (TEE) over 2-3 d in seven boys (mean +/- SD age 9.4+/-0.4 yr) by the Flex heart rate (HR) method.


METHODS
HR and oxygen consumption were measured simultaneously for eight activities (lying, sitting, standing, arm-reaching exercise, a stooping-and-twisting exercise, stepping, treadmill walking/running, and cycle ergometry) carried out in sequence. CE were derived from various combinations of activities. Flex HRs were identified for each CE.


RESULTS
There were no significant differences in TEE estimates [range (mean +/- SD); 6.65+/-0.72 to 7.27+/-0.89 MJ x d(-1)] derived from any of the CE. Mean daytime HR ranged from 86+/-4 to 122+/-15 beats x min(-1), and 82-98% of recorded daytime HR was < or = 140 beats x min(-1). As a result, within-subject CV in TEE from each of the CE ranged from 2.2% to 8.9%. Mean between-subject Flex HR ranged from 94+/-8 to 111+/-8 beats x min(-1). No significant differences were observed in corresponding TEE estimates. However, mean activity energy expenditure (AEE) ranged from 2.10+/-1.18 MJ x d(-1) (based on Flex HR 111+/-8 beats-min(-1)) to 3.55+/-1.44 MJ x d(-1) (based on Flex HR 94+/-8 beats x min(-1); NS). The corresponding estimates of resting energy expenditure (REE) were 1.89+/-0.82 MJ x d(-1) (Flex HR 111+/-8 beats-min(-1)) and 1.05+/-0.60 MJ x d(-1) (Flex HR 94+/-8 beats x min(-1)). Only the differences between the minimum and maximum estimates of REE were significant (P < 0.05).


CONCLUSIONS
Unduly lengthy and complex calibration procedures for the estimation of Flex HR TEE may not be justified in most cases, particularly in sedentary children.
Livingstone
M B
MB
Northern Ireland Centre for Diet and Health, University of Ulster, Coleraine, Co. Londonderry. mbe.livingstone@ulst.ac.uk
Robson
P J
PJ
Totton
M
M
D002138:Calibration; D002648:Child; D004734:Energy Metabolism; D005069:Evaluation Studies as Topic; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D010101:Oxygen Consumption