Abstract
Available evidence indicates that ketone bodies inhibit glycolysis in contracting muscles. Therefore, we investigated whether acute exogenous ketosis by oral ketone ester (KE) intake early in a simulated cycling race can induce transient glycogen sparing by glycolytic inhibition, thereby increasing glycogen availability in the final phase of the event. In a randomized crossover design, 12 highly trained male cyclists completed a simulated cycling race (RACE), which consisted of 3-h intermittent cycling (IMT180′), a 15-min time trial (TT15′), and a maximal sprint (SPRINT). During RACE, subjects received 60 g carbohydrates/h combined with three boluses (25, 20, and 20 g) (R)-3-hydroxybutyl (R)-3-hydroxybutyrate (KE) or a control drink (CON) at 60 and 20 min before and at 30 min during RACE. KE intake transiently increased blood d-β-hydroxybutyrate to ~3 mM (range: 2.6–5.2 mM) during the first half of RACE (P < 0.001 vs. CON). Blood pH concomitantly decreased from approximately 7.42 to 7.36 (range: 7.29–7.40), whereas bicarbonate dropped from 26.0 to 21.6 mM (range: 20.1–23.7; both P < 0.001 vs. CON). Net muscle glycogen breakdown during IMT180′ [KE: −78 ± 30 (SD); CON: −60 ± 22 mmol/kg wet wt; P = 0.08] and TT15′ (KE: −9 ± 18; CON: −18 ± 18 mmol/kg wet wt; P = 0.35) was similar between KE and CON. Accordingly, mean power output during TT15′ (KE: 273 ± 38; CON: 272 ± 37 W; P = 0.83) and time-to-exhaustion in the SPRINT (KE: 59 ± 16; CON: 58 ± 17 s; P = 0.66) were similar between conditions. In conclusion, KE intake during a simulated cycling race does not cause glycogen sparing, nor does it affect all-out performance in the final stage of a simulated race.NEW & NOTEWORTHY Exogenous ketosis produced by oral ketone ester ingestion during the early phase of prolonged endurance exercise and against the background of adequate carbohydrate intake neither causes muscle glycogen sparing nor improves performance in the final stage of the event. However, such exogenous ketosis may decrease buffering capacity in the approach of the final episode of the event. Furthermore, ketone ester intake during exercise may reduce appetite immediately after exercise.
Highlights
Endurance exercise performance is largely determined by the ability of the body to generate sustained muscular work, which largely depends on muscular oxygen supply via cardiac output as well as ATP production via oxidative energy turnover [10, 13, 14]
Following ketone monoester (R)-3-hydroxybutyl (R)-3-hydroxybutyrate (KE) ingestion, blood HB increased to peak level within 30 min, causing a stable physiological ketosis of approximately 2–3 mM during the initial 2 h of IMT180= (P Ͻ 0.001 vs. baseline)
Ketosis-induced glycogen sparing conceivably may be ergogenic in prolonged endurance exercise events wherein a low-to-moderate-intensity initial phase is followed by a highintensity final part involving intermittent short maximal exercise bouts and sprinting
Summary
Endurance exercise performance is largely determined by the ability of the body to generate sustained muscular work, which largely depends on muscular oxygen supply via cardiac output as well as ATP production via oxidative energy turnover [10, 13, 14]. Higher relative substrate availability results in greater fractional utilization [30]. From this perspective, numerous studies have explored the effect of changing substrate availability by dietary manipulation on endurance exercise performance [4, 27]. Numerous studies have explored the effect of changing substrate availability by dietary manipulation on endurance exercise performance [4, 27] These studies showed general improvements in performance with high-carbohydrate intake compared with consumption of large amounts of fat in events lasting Ն1 h [6, 48]. High-carbohydrate intake before and during exercise is still considered as the optimal choice to attain maximal endurance exercise performance [28]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
