Ketone Ester Supplementation Does Not Enhance Markers Of Recovery Following Endurance Exercise In Trained Male Cyclists

Recent studies have explored whether exogenous ketone esters (KE) may represent an alternative fuel source to support exercise and subsequent recovery. While the evidence to support ketone use during exercise is mixed, initial findings suggest supplementing with KE may promote post-exercise muscle recovery. Therefore, the purpose of this study was to determine the effects of including KE or placebo (PL) as part of a recovery beverage on whole-body and skeletal muscle responses to an acute bout of endurance exercise in trained cyclists. METHODS: In a dietary controlled randomised crossover design, 8 well-trained (Tier 2-3) male cyclists (n = 8, V̇O2peak 63.8 ± 4.9 mL/min/kg, wattage max (Wmax) 403 ± 34 W) completed a 3 h intermittent intensity ride (60-85% of Wmax) prior to consuming either 573 mg/kg body mass (BM) KE or PL in a recovery shake containing 3 g/kg BM carbohydrate and 0.3 g/kg BM protein. Maintenance doses (287 mg/kg KE or PL) were consumed every hour during the 5 h recovery period. Blood samples were collected after an overnight fast, pre-exercise (post prandial), and hourly for 5 h post-exercise. Skeletal muscle biopsies were taken immediately post-exercise (0 h) and 2 and 5 h into the recovery period. RESULTS: Despite the significant increase in circulating β-hydroxybutyrate availability following KE ingestion (area under the curve; AUC, p < 0.001 vs. PL), skeletal muscle signalling responses post exercise were unaltered compared to PL. Specifically, while signalling was impacted by the exercise bout (effect of time, p < 0.05), there were no differences between treatments in phosphorylated/total protein levels linked to energy status (AMPK Thr172, p = 0.935), or surrogate markers for muscle protein synthesis including mTOR Ser2448 (p = 0.215) and its downstream targets 4E-BP1, eEF2, or eIF2 (all p > 0.100). Similarly, no differences were detected between treatments on hormone levels including testosterone (AUC, p = 0.162), and erythropoietin (AUC, p = 0.645). CONCLUSION: Inclusion of KE in a post-exercise recovery beverage increases circulating ketone levels but failed to augment markers of whole-body and skeletal muscle recovery and adaptation including circulating hormone concentrations and skeletal muscle signalling responses linked to muscle protein synthesis. Supported by: This study was supported by Australian Catholic University research funding awarded to J.A. Hawley and L.M. Burke.