Author(s): PHILLIPS, R., BROUNER, J., SPENDIFF, O., Institution: KINGSTON UNIVERSITY LONDON, Country: UNITED KINGDOM, Abstract-ID: 2182

INTRODUCTION:
Exogenous ketone ester (KE) ingestion elevates circulating beta hydroxybutyrate (BHB) and alters substrate availability during exercise, yet performance effects remain equivocal and may depend on habitual diet. This study tested whether acute R-3-hydroxybutyl R-3-hydroxybutyrate affects aerobic capacity, submaximal physiological responses, and repeated sprint performance in recreationally active adults habitually consuming either a ketogenic diet (KD) or a high carbohydrate diet (HC).
METHODS:
Recreationally active adults (n=19) completed a randomised, single blind, placebo controlled, crossover design. Participants ingested KE (330 mg/kg) or placebo (PLA) prior to a cycling maximal oxygen uptake test (VO2max). Capillary blood glucose, lactate, and BHB were sampled pre exercise, at 5 min intervals during the VO2max test, and immediately post exercise. On a separate visit, supplementation was repeated before 60 min cycling at 55% of WMax followed immediately by 5 x 10 s Wingate sprints. During the 60 min bout, blood variables were sampled at 0, 20, 40, and 60 min. During the Wingate protocol, blood measures were obtained after each sprint. Two-way mixed ANOVA tested Condition (KE vs PLA), Diet (KD vs HC), and Condition x Diet. Significance was set at p<0.05.
RESULTS:
No significant main or interaction effects were observed for VO2max. During 60 min cycling, KE increased BHB at 0 min (p=0.015), 20 min (p<0.001), 40 min (p<0.001), and 60 min (p<0.001). A Condition x Diet interaction was observed for BHB at 20 min only (p<0.001). Blood glucose was reduced at 40 min (p=0.002) and blood lactate was reduced at 40 min (p=0.003) and 60 min (p=0.003). Mean respiratory exchange ratio (RER) decreased (p=0.016) and mean VO2 increased (p=0.042) during the 60 min bout. In the Wingate test, peak cadence demonstrated a Condition x Diet interaction (p=0.007), while no significant interactions were observed for peak power, mean power, power per kg, speed, or distance.
CONCLUSION:
Acute KE ingestion produced significant metabolic alterations during submaximal exercise, with diet specific effects confined to early BHB kinetics and peak cadence. These changes did not translate into improvements in VO2max or repeated sprint power, suggesting diet dependent metabolic effects without clear performance enhancement.