Related Experiment Video
Updated: Jun 30, 2026
Using a Combination of Indirect Calorimetry, Infrared Thermography, and Blood Glucose Levels to Measure Brown Adipose Tissue Thermogenesis in Humans
Published on: June 2, 2023
Methodological aspects of crossover and maximum fat-oxidation rate point determination
A-S Michallet1, J Tonini, J Regnier
1Laboratoire de recherche-exercice, santé REX-S, IFR 1, hôpital Sud, université Joseph-Fourier Grenoble-1, BP 338, 38043 Echirolles cedex, France; Inserm, ERI17, laboratoire HP2, université Joseph-Fourier Grenoble-1, 38042 Grenoble, France.
The analytical device and exercise protocol significantly impact metabolic indices like crossover point (COP) and maximum fat oxidation rate (LIPOXmax). Using the true maximum aerobic power (MAP) protocol with a Douglas bag is recommended for accurate results in fit individuals.
Area of Science:
- Exercise Physiology
- Metabolic Research
- Sports Science
Background:
- Indirect calorimetry during exercise yields metabolic indices of substrate oxidation balance: crossover point (COP) and maximum fat oxidation rate (LIPOXmax).
- Variability in these indices can be influenced by analytical devices, protocol types, and ventilatory responses.
Purpose of the Study:
- To investigate the impact of analytical devices, protocol types, and ventilatory responses on the variability of COP and LIPOXmax.
- To examine the relationship between these metabolic indices and lactate and ventilation thresholds.
Main Methods:
- 14 relatively fit subjects underwent maximum exercise testing followed by three submaximum graded tests.
- Tests utilized either a theoretical maximum power (tMAP) or true maximum aerobic power (MAP) reference.
- Gas exchange was measured using both a Douglas bag (D) and an ergospirometer (E).
Main Results:
- Metabolic indices were interpretable only with the Douglas bag (D) reference method and MAP protocol.
- The ergospirometer (E) overestimated both indices compared to the Douglas bag (D).
- Ventilation accounted for 10-16% of metabolic index variations; COP correlated with ventilation and blood lactate increase, while LIPOXmax correlated with the ventilation threshold.
Conclusions:
- Analytical device, protocol reference, and ventilation responses influence metabolic indices in fit, healthy subjects.
- A protocol based on true MAP or adapted for fat-to-carbohydrate transition is recommended for interpretable results.
- Metabolic indices correlate with lactate/ventilation thresholds, suggesting shorter maximal exercise tests may estimate them in fit individuals, warranting confirmation in patients with metabolic defects.
