Abstract: | Moon, Jon K., and Nancy F. Butte. Combined heart rateand activity improve estimates of oxygen consumption and carbon dioxideproduction rates. J. Appl. Physiol.81(4): 1754-1761, 1996.Oxygen consumption(O2) andcarbon dioxide production (CO2) rates were measuredby electronically recording heart rate (HR) and physical activity (PA).Mean daily O2 andCO2 measurements by HR andPA were validated in adults (n = 10 women and 10 men) with room calorimeters. Thirteen linear and nonlinear functions of HR alone and HR combined with PA were tested as models of24-h O2 andCO2. Mean sleepO2 andCO2 were similar to basalmetabolic rates and were accurately estimated from HR alonerespective mean errors were 0.2 ± 0.8 (SD) and0.4 ± 0.6%]. The range of prediction errorsfor 24-h O2 andCO2 was smallestfor a model that used PA to assign HR for each minute to separateactive and inactive curves(O2, 3.3 ± 3.5%; CO2, 4.6 ± 3%). There were no significant correlations betweenO2 orCO2 errors and subject age,weight, fat mass, ratio of daily to basal energy expenditure rate, orfitness. O2,CO2, and energy expenditurerecorded for 3 free-living days were 5.6 ± 0.9 ml · min1 · kg1,4.7 ± 0.8 ml · min1 · kg1,and 7.8 ± 1.6 kJ/min, respectively. Combined HR and PA measured 24-h O2 andCO2 with a precisionsimilar to alternative methods. |