Inter-Day Reliability of Resting Metabolic Rate and Maximal Fat Oxidation during Exercise in Healthy Men Using the Ergostik Gas Analyzer Robles-González, Lidia Gutiérrez Hellín, Jorge Aguilar Navarro, Millán Ruiz Moreno, Carlos Muñoz, Alejandro Del Coso, Juan Ruiz Ruiz, Jonatan Amaro Gahete, Francisco José Reproducibility RMR RER MFO Fatmax Metabolic rate The attainment of high inter-day reliability is crucial to determine changes in resting metabolic rate (RMR), respiratory exchange ratio (RER), maximal fat oxidation during exercise (MFO) and the intensity that elicits MFO (Fatmax) after an intervention. This study aimed to analyze the inter-day reliability of RMR, RER, MFO and Fatmax in healthy adults using the Ergostik gas analyzer. Fourteen healthy men (age: 24.4 ± 5.0 years, maximum oxygen uptake (VO2max): 47.5 ± 11.9 mL/kg/min) participated in a repeated-measures study. The study consisted of two identical experimental trials (Day 1 and Day 2) in which the participants underwent an indirect calorimetry assessment at resting and during an incremental exercise test. Stoichiometric equations were used to calculate energy expenditure and substrate oxidation rates. There were no significant differences when comparing RMR (1999.3 ± 273.9 vs. 1955.7 ± 362.6 kcal/day, p = 0.389), RER (0.87 ± 0.05 vs. 0.89 ± 0.05, p = 0.143), MFO (0.32 ± 0.20 vs. 0.31 ± 0.20 g/min, p = 0.776) and Fatmax (45.0 ± 8.6 vs. 46.4 ± 8.4% VO2max, p = 0.435) values in Day 1 vs. Day 2. The inter-day coefficient of variation for RMR, RER, MFO and Fatmax were 4.85 ± 5.48%, 3.22 ± 3.14%, 7.78 ± 5.51%, and 6.51 ± 8.04%, respectively. In summary, the current results show a good inter-day reliability when RMR, RER, MFO and Fatmax are determined in healthy men using the Ergostik gas analyzer. 2021-11-30T09:02:40Z 2021-11-30T09:02:40Z 2021 journal article Robles-González, L.; Gutiérrez-Hellín, J.; Aguilar-Navarro, M.; Ruiz-Moreno, C.; Muñoz, A.; Del-Coso, J.; R. Ruiz, J.; Amaro-Gahete, F.J. Inter-Day Reliability of Resting Metabolic Rate and Maximal Fat Oxidation during Exercise in Healthy Men Using the Ergostik Gas Analyzer. Nutrients 2021, 13, 4308. https://doi.org/10.3390/ nu13124308 http://hdl.handle.net/10481/71829 10.3390/nu13124308 eng http://creativecommons.org/licenses/by/3.0/es/ open access Atribución 3.0 España MDPI