Concordance between 13C:12C ratio technique respect to indirect calorimetry to estimate carbohydrate and Fat oxidation rates by means stoichiometric equations during exercise. A reliability and agreement study

摘要

Indirect calorimetry is a tool used routinely by sport/exercise physiologist to assess the metabolic response to training and to nutritional interventions. There are different stoichiometric equations to estimate fat (FatOxR) and carbohydrates (CHOO xR) oxidation rates, however there are not enough information in literature about what are the most accurate equations. The purpose of this study was to determine the concordance between indirect calorimetry and a method of reference for stoichiometric equations used to estimate FatOxR and CHOO xR. Concordance between indirect calorimetry and the method of reference (¹³C to ¹²C ratio (¹³C:¹²C ratio) technique) for key stoichiometric equations was assessed in well‐trained triathletes. Subjects carried out a carbohydrate depletion‐repletion protocol, labeling the glycogen stores with ¹³C, and a laboratory test to assess the ¹³C metabolic response during a wide range of aerobic intensities during exercise. All the equations showed a narrow agreement interval (Δ) (CHOO xR nPC (protein component negligible): −0.308, 0.308, CHOO xR PC (protein component): −0.268, 0.268, FatOxR nPC and PC: −0.032, 0.032 (g·min⁻¹)). FatOxR showed a similar concordance (28–32%) with CHOO xR nPC ranging from 55% to 75%, and for CHOO xR PC between 51% to 71%. None of the stoichiometric equations met a perfect agreement with the method of reference. The Jeukendrup and Wallis equation showed the best concordance for CHO_{O xR} nPC whilst the Frayn and Ferrannini (Glu) equations had the best agreement for CHO_{O xR} PC. All Fat_OxR equations showed similar concordances and they are able to be used indistinctly.