title: Use of [14C]-sodium bicarbonate/urea to measure physical activity induced increases in total energy expenditure in free-living healthy males.
abstract: The aim of this study was to evaluate the utility of the [(14)C]-sodium bicarbonate/urea technique to detect physical activity-induced increases in total energy expenditure in free-living healthy men. Thirteen healthy males aged 34.1 +/- 11.7 yrs with body mass index 24.1 +/- 3.1 kg/m(2) were studied on three separate occasions, during which [(14)C]-bicarbonate was infused over 48-hours and urine was collected during the second 24-hours. On three separate occasions and in random order, subjects either remained sedentary, or performed a bout of physical activity on an electro-magnetically braked cycle ergometer sufficient to increase energy expenditure by 7% or 11% above predicted sedentary total energy expenditure. Urine samples were analyzed to evaluate the amount of [(14)C]-bicarbonate incorporated into urinary urea, thereby reflecting the amount of CO(2) produced per day, and upon conversion, the number of kilojoules of energy expended in 24-hours. All 13 subjects successfully completed the two physical activity treatments and there were no adverse events. As measured by the [(14)C]-urea assay, mean total energy expenditure values were not significantly different between sedentary activity (17902 +/- 905 kJ/day), the physical activity treatment designed to increase TEE by 7% (17701 +/- 594 kJ/day) and the physical activity treatment designed to increase TEE by 11% (18538 +/- 485 kJ/day) (P=0.668). In conclusion, although the [(14)C]-sodium bicarbonate/urea technique was well tolerated and did not interfere with normal daily activities, it was not able to accurately measure physical activity-induced increases in EE in the range of 7-11% above predicted sedentary total energy expenditure.
authors.affiliation: Department of Medicine, University of Adelaide, Royal Adelaide Hospital, Adelaide SA 5000, Australia.
authors.forename: Darren M
authors.initials: DM
authors.lastname: Roffey
authors.forename: Natalie D
authors.initials: ND
authors.lastname: Luscombe
authors.forename: Nuala M
authors.initials: NM
authors.lastname: Byrne
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Hills
authors.forename: Max
authors.initials: M
authors.lastname: Bellon
authors.forename: Chris
authors.initials: C
authors.lastname: Tsopelas
authors.forename: Ian D
authors.initials: ID
authors.lastname: Kirkwood
authors.forename: Gary A
authors.initials: GA
authors.lastname: Wittert
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001481:Basal Metabolism; D015992:Body Mass Index; D002245:Carbon Dioxide / Q000378:metabolism; D002250:Carbon Radioisotopes / Q000652:urine; D004734:Energy Metabolism / Q000502:physiology*; D016552:Ergometry; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D017693:Sodium Bicarbonate / Q000652:urine*; D014508:Urea / Q000652:urine*
chemical_list: D002250:Carbon Radioisotopes; D002245:Carbon Dioxide; D017693:Sodium Bicarbonate; D014508:Urea