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Environmental heat stress offsets adaptation associated with carbohydrate periodization in trained male triathletes

Bennett, SJ, Tiollier, E, Guibert, E, Morales-Artacho, A, Lalire, P, Owens, DJ, Morton, JP, Brocherie, F and Louis, J (2023) Environmental heat stress offsets adaptation associated with carbohydrate periodization in trained male triathletes. Scandinavian Journal of Medicine and Science in Sports. ISSN 0905-7188

Bennett et al. 2023 SJMSS (SLTL in the heat).pdf - Published Version
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Purpose: Carbohydrate (CHO) intake periodization via the sleep low train low (SL-TL) diet–exercise model increases fat oxidation during exercise and may enhance endurance-training adaptation and performance. Conversely, training under environmental heat stress increases CHO oxidation, but the potential of combined SL-TL and heat stress to enhance metabolic and performance outcomes is unknown.
Methods: Twenty-three endurance-trained males were randomly assigned to either control (n = 7, CON), SL-TL (n = 8, SLTemp) or SL-TL + heat stress (n = 8, SLHeat) groups and prescribed identical 2-week cycling training interventions. CON and SLTemp completed all sessions at 20°C, but SLHeat at 35°C. All groups consumed matched CHO intake (6 g·kg−1·day−1) but timed differently to promote low CHO availability overnight and during morning exercise in both SL groups. Submaximal substrate utilization was assessed (at 20°C), and 30-min performance tests (at 20 and 35°C) were performed Pre-, Post-, and 1-week post-intervention (Post+1).
Results: SLTemp improved fat oxidation rates at 60% MAP (~66% VO2peak) at Post+1 compared with CON (p < 0.01). Compared with SLTemp, fat oxidation rates were significantly lower in SLHeat at Post (p = 0.02) and Post+1 (p < 0.05). Compared with CON, performance was improved at Post in SLTemp in temperate conditions. Performance was not different between any groups or time points in hot conditions.
Conclusion: SL-TL enhanced metabolic adaptation and performance compared with CON and combined SL-TL and heat stress. Additional environmental heat stress may impair positive adaptations associated with SL-TL.

Item Type: Article
Uncontrolled Keywords: Cycling performance; Diet-exercise strategy; Endurance training; Heat acclimation; metabolism; Nutrition; 1106 Human Movement and Sports Sciences; 1116 Medical Physiology; Sport Sciences
Subjects: R Medicine > RC Internal medicine > RC1200 Sports Medicine
Divisions: Sport & Exercise Sciences
Publisher: Wiley
SWORD Depositor: A Symplectic
Date Deposited: 16 Jun 2023 10:53
Last Modified: 16 Jun 2023 11:00
DOI or ID number: 10.1111/sms.14430
URI: https://researchonline.ljmu.ac.uk/id/eprint/19883
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