Daily energy expenditure in free-living children: comparison of heart-rate monitoring with the doubly labeled water (2H218O) method

Total energy expenditure (TEE) was measured simultaneously in 36 free-living children aged 7, 9, 12, and 15 y over 10–15 d by the doubly labeled water (DLW) method and for 2–3 separate days by heart-rate (HR) monitoring. The 95% confidence limits of agreement (mean difference ± 2SD) were −1.99 to +1.44 MJ/d. HR TEE discrepancies ranged from −16.7% to +18.8% with 23 values lying within ± 10% of DLW TEE estimates. Boys and girls spent 462 ± 108 and 318 ± 120 min/d, respectively, in total physical activity (P < 0.01). Time spent in moderate and vigorous physical activity (MVPA) was 68 ± 37 min/d by younger children (7–9 y) and 34 ± 24 min/ d by older children (12–15 y) (P < 0.001). Younger boys engaged in MVPA (91 ±33 min/d) and vigorous physical activity (VPA) (35 ± 15 min/d) significantly longer than younger girls (MVPA, 39 ± 16 min/d,P < 0.001; VPA, 10 ± 4 min/d,P < 0.01) as did older boys (MVPA, 52 ± 21 min/d; VPA, 30 ± 18 min/d) compared with older girls (MVPA, 15 ± 10 min/d; VPA, 8 ± 5 min/d). HR monitoring provides a close estimation of the TEE of population groups and objective assessment of associated patterns of physical activity.