CLIMATE-RELATED CORRECTIONS FOR IMPROVED ESTIMATION OF ENERGY-EXPENDITURE FROM HEART-RATE IN CHILDREN

The purpose of this study was to determine the relationship between children's heart rate (HR) and climatic heat stress at several O-2 uptake (V over dot O-2) levels and to construct equations and nomograms for an improved estimation of energy expenditure (EE) from HR monitoring. On four occasions 12 boys and 8 girls (8-11 yr) cycled for 5 min each at 35, 55, and 75% of peak V over dot O-2 (random order), with rest periods in between, in a climatic chamber. The randomly assigned conditions were 22 degrees C dry bulb temperature, 50% relative humidity (RH); 28 degrees C, 55% RH; 32 degrees C, 52% RH; or 35 degrees C, 58% RH. HR and V over dot O-2 were determined during the final 2 min of rest and exercise bouts. HR measured at a dry bulb temperature (T) (HR(meas)) was then related to a HR at 22 degrees C that would have been expected to occur at an identical V over dot O-2 (HR(calc22)) by using individual 22 degrees C HR-V over dot O-2 regression Lines. HR(calc22) could be estimated from HR(meas).[1.175032-(0.007956 . T)], with a mean error of prediction for the entire group <1.5 beats/min for each temperature. The following conclusions were drawn: 1) children's HR at a given V over dot O-2 increases Linearly with ambient temperature at 22-35 degrees C, 50-60% RH; and 2) HR can be corrected for the influence of climate in groups of children resting and exercising at the above conditions, thereby reducing the error of estimating EE from HR.