University of Oulu

McCue, A., Munten, S., Herzig, K.-H., & Gagnon, D. D. (2021). Metabolic flexibility is unimpaired during exercise in the cold following acute glucose ingestion in young healthy adults. Journal of Thermal Biology, 98, 102912.

Metabolic flexibility is unimpaired during exercise in the cold following acute glucose ingestion in young healthy adults

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Author: McCue, Alexus1,2; Munten, Stephanie1,2; Herzig, Karl-Heinz3,4;
Organizations: 1Laboratory of Environmental Exercise Physiology, School of Kinesiology and Health Sciences, Laurentian University, Sudbury, Ontario, Canada
2Center of Research in Occupational Health and Safety, Laurentian University, Sudbury, Ontario, Canada
3Institute of Biomedicine, Medical Research Center, Faculty of Medicine, University of Oulu, Oulu University Hospital, Oulu, Finland
4Department of Gastroenterology and Metabolism, Poznan University of Medical Sciences, Poznan, Poland
Format: article
Version: accepted version
Access: open
Online Access: PDF Full Text (PDF, 0.1 MB)
Persistent link:
Language: English
Published: Elsevier, 2021
Publish Date: 2022-04-07


Purpose: Metabolic flexibility is compromised in individuals suffering from metabolic diseases, lipo- and glucotoxicity, and mitochondrial dysfunctions. Exercise studies performed in cold environments have demonstrated an increase in lipid utilization, which could lead to a compromised substrate competition, glycotoxic-lipotoxic state, or metabolic inflexibility. Whether metabolic flexibility is altered during incremental maximal exercise to volitional fatigue in a cold environment remains unclear.

Methods: Ten young healthy participants performed four maximal incremental treadmill tests to volitional fatigue, in a fasted state, in a cold (0 °C) or a thermoneutral (22.0 °C) environment, with and without a pre-exercise ingestion of a 75-g glucose solution. Metabolic flexibility was assessed via indirect calorimetry using the change in respiratory exchange ratio (ΔRER), maximal fat oxidation (ΔMFO), and where MFO occurred along the exercise intensity spectrum (ΔFatmax), while circulating lactate and glucose levels were measured pre and post exercise.

Results: Multiple linear mixed-effects regressions revealed an increase in glucose oxidation from glucose ingestion and an increase in lipid oxidation from the cold during exercise (p < 0.001). No differences were observed in metabolic flexibility as assessed via ΔRER (0.05 ± 0.03 vs. 0.05 ± 0.03; p = 0.734), ΔMFO (0.21 ± 0.18 vs. 0.16 ± 0.13 g min−1; p = 0.133) and ΔFatmax (13.3 ± 19.0 vs. 0.6 ± 21.3 %V̇O2peak; p = 0.266) in cold and thermoneutral, respectively.

Conclusions: Following glucose loading, metabolic flexibility was unaffected during exercise to volitional fatigue in a cold environment, inducing an increase in lipid oxidation. These results suggest that competing pathways responsible for the regulation of fuel selection during exercise and cold exposure may potentially be mechanistically independent. Whether long-term metabolic influences of high-fat diets and acute lipid overload in cold and warm environments would impact metabolic flexibility remain unclear.

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Series: Journal of thermal biology
ISSN: 0306-4565
ISSN-E: 1879-0992
ISSN-L: 0306-4565
Volume: 98
Article number: 102912
DOI: 10.1016/j.jtherbio.2021.102912
Type of Publication: A1 Journal article – refereed
Field of Science: 3111 Biomedicine
Funding: Dr. D.D. Gagnon is supported by a Natural Sciences and Engineering Research Council of Canada Discovery Grant (Grant number: NSERC 2016-060883).
Copyright information: © 2021. This manuscript version is made available under the CC-BY-NC-ND 4.0 license