Approximate Time to Steady-state Resting Energy Expenditure Using Indirect Calorimetry in Young, Healthy Adults

Abstract

Indirect calorimetry (IC) measurements to estimate resting energy expenditure (REE) necessitate a stable measurement period or steady state (SS). There is limited evidence when assessing the time to reach SS in young, healthy adults. The aims of this prospective study are to determine the approximate time to necessary reach SS using open-circuit IC and to establish the appropriate duration of SS needed to estimate REE. One hundred young, healthy participants (54 males and 46 females; age = 20.6 ± 2.1 years; body weight = 73.6 ± 16.3 kg; height 172.5 ± 9.3 cm; BMI = 24.5 ± 3.8 kg/m2) completed IC measurement for approximately 30 min while the volume of oxygen (VO2) and volume of carbon dioxide (VCO2) were collected. SS was defined by variations in the VO2 and VCO2 of ≤10% coefficient of variation (%CV) over a period of five consecutive minutes. The 30-min IC measurement was divided into six 5-min segments, such as S1, S2, S3, S4, S5, and S6. The results show that SS was achieved during S2 (%CV = 6.81 ± 3.2%), and the %CV continued to met the SS criteria for the duration of the IC measurement (S3 = 8.07 ± 4.4%, S4 = 7.93 ± 3.7%, S5 = 7.75 ± 4.1%, and S6 = 8.60 ± 4.6%). The current study found that in a population of young, healthy adults the duration of the IC measurement period could be a minimum of 10 min. The first 5-min segment was discarded, while SS occurred by the second 5-min segment.

The use of a portable metabolic monitoring device for measuring RMR in healthy adults

“…For example, although the best practice guideline recommends at least 20-min rest before the RMR measurement (13) , recent studies among healthy young adults showed that a resting period before the RMR measurement could be omitted. In previous studies, during the 30-min RMR measurement, a steady state was achieved after 5 min and there was no difference in RMR between each of the 5-min segment after the first 5 min (18,19) . Therefore, in this study, a rest period prior to both the RMR measurements was not imposed in order to minimise the total duration, to create a comfortable testing environment and to mimic the practicality in clinical practice.…”

“…Comparing the percentage of participants reaching a steady state with previous studies using either QUARK RMR or Fitmate GS is not possible because the criteria for the steady state were not defined and the percentage of participants who reached the steady state was not reported (9)(10)(11)44) . Studies using a canopy hood but different metabolic monitoring devices reported that 93-95 % of healthy adults reached a steady state over five consecutive minutes within the 30 min (18,48) . Portable metabolic monitoring device 5…”

“…After the first RMR measurement, participants were given a standardised break in which they were instructed to take a walk over a standardised trajectory at their usual pace for 10 min to interrupt the steady state achieved in the first RMR measurement and to align pre-test conditions (i.e. no prior resting period) (18,19) for the measurements with the second device. The first 5 min of the data from both the measurements was discarded because the participants had to adapt their breathing while wearing the canopy hood (13,20) .…”

Postural Hypotension and Cognitive Function in Older Adults

“…Average Cardiac Index levels started out at 3.3 L/min/m 2 upon sitting, consistent with the CI expected of this age group when supine (4.87-0.023 × age; Katori, 1979 ), then fell by one third to below 2.2 L/min after 30 min of sitting. This long-duration continuous drop in CI is very different than that seen in young adults, where changes in resting metabolic rate (a surrogate measure of cardiac index) have been shown to plateau in 10 to 15 min ( Popp, Risch, Sakarcan, Bridges, & Jesch, 2016 ). However, these results are consistent with recent work assessing lower limb fluid pooling which show that fluid pooling in older adults (40-70 years) can progress for more than 4 hr ( Singh, Yadollahi, Lyons, Alshaer, & Bradley, 2017 ).…”

Prolonged standing reduces fasting plasma triglyceride but does not influence postprandial metabolism compared to prolonged sitting

“…Subjects were asked to relax and breathe normally while sitting or standing. Subjects rested for 20 minutes before gas samples were collected to allow for a steady state to be reached [15]. During the last ten minutes of each 30-minute period each subject breathed into a meteorological balloon using a one-way valve (Hans Rudolph, Kansas City, MO).…”