The Effect of Blood Ketone Concentration and Exercise Intensity on Exogenous Ketone Oxidation Rates in Athletes.

Publisher: Lippincott Williams & Wilkins Country of Publication: United States NLM ID: 8005433 Publication Model: Print Cited Medium: Internet ISSN: 1530-0315 (Electronic) Linking ISSN: 01959131 NLM ISO Abbreviation: Med Sci Sports Exerc Subsets: MEDLINE

Publication: Hagerstown, Md : Lippincott Williams & Wilkins
Original Publication: Madison, Wis., American College of Sports Medicine.

Athletes*; 3-Hydroxybutyric Acid/*metabolism ; Energy Metabolism/*physiology ; Exercise/*physiology ; Ketones/*blood ; Muscle, Skeletal/*metabolism; 3-Hydroxybutyric Acid/administration & dosage ; 3-Hydroxybutyric Acid/blood ; 3-Hydroxybutyric Acid/urine ; Cross-Over Studies ; Exercise Test ; Female ; Glycogen/metabolism ; Humans ; Ketones/administration & dosage ; Ketosis/metabolism ; Male ; Muscle Fibers, Skeletal/metabolism ; Oxidation-Reduction ; Physical Exertion ; Single-Blind Method ; Time Factors ; Young Adult

Introduction: Exogenous ketones potentially provide an alternative, energetically advantageous fuel to power exercising skeletal muscle. However, there is limited evidence regarding their relative contribution to energy expenditure during exercise. Furthermore, the effect of blood ketone concentration and exercise intensity on exogenous ketone oxidation rates is unknown.
Methods: Six athletes completed cycling ergometer exercise on three occasions within a single-blind, random-order controlled, crossover design study. Exercise duration was 60 min, consisting of 20-min intervals at 25%, 50%, and 75% maximal power output (WMax). Participants consumed (i) bitter flavored water (control), (ii) a low-dose β-hydroxybutyrate (βHB) ketone monoester (KME; 252 mg·kg BW-1, "low ketosis"), or (iii) a high-dose βHB KME (752 mg·kg BW-1, "high ketosis"). The KME contained a 13C isotope label, allowing for the determination of whole-body exogenous βHB oxidation rates through sampled respiratory gases.
Results: Despite an approximate doubling of blood βHB concentrations between low- and high-ketosis conditions (~2 mM vs ~4.4 mM), exogenous βHB oxidation rates were similar at rest and throughout exercise. The contribution of exogenous βHB oxidation to energy expenditure peaked during the 25% WMax exercise intensity but was relatively low (4.46% ± 2.71%). Delta efficiency during cycling exercise was significantly greater in the low-ketosis (25.9% ± 2.1%) versus control condition (24.1% ± 1.9%; P = 0.027).
Conclusions: Regardless of exercise intensity, exogenous βHB oxidation contributes minimally to energy expenditure and is not increased by elevating circulating concentrations greater than ~2 mM. Despite low exogenous βHB oxidation rates, exercise efficiency was significantly improved when blood βHB concentration was raised to ~2 mM.
(Copyright © 2020 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American College of Sports Medicine.)

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0 (Ketones)
9005-79-2 (Glycogen)
TZP1275679 (3-Hydroxybutyric Acid)

Date Created: 20200902 Date Completed: 20210617 Latest Revision: 20230822

20240628

PMC7886359

10.1249/MSS.0000000000002502

32868580