Background: The acute ingestion of ketone body supplements can improve exercise responses such as oxygen consumption and blood lactate. Additionally, ketone body supplements show increases in circulating ßhb concentration, matching those of someone in a state of nutritional ketosis. Studies testing ketone body supplements have reported different results in exercise response and varying gastrointestinal discomfort. Objectives: This study aimed to compare the effects of exogenous ketone supplements on submaximal exercise response in a group of trained male cyclists. Methods. A randomized, double-blind study was conducted. Forty-four males were randomly assigned to one of four supplement groups, i.e., high ketone (HKET) (10g ßhb); low ketone (LKET) (4g ßhb); carbohydrate (CHO); or placebo (PLA). Oxygen consumption and blood lactate were measured as markers of exercise response and blood ßhb as a marker for ketosis, during a submaximal cycle protocol (30 min at 60% VO2max). Results: Two of the three supplements increased oxygen consumption (CHO: p<0.0005; and HKET: p=0.015). The HKET group experienced an increase in maximal blood lactate (P = 0.010) and a decrease in lactate threshold (d=0.93). Additionally, the HKET group showed the largest increase in circulating ßhb concentration (P = 0.004) 30 minutes following ingestion. The respiratory exchange ratio, heart rate, and plasma glucose were not affected. Conclusion: Although the exogenous ketone supplements were able to induce a mild state of ketosis (>0.5 mmol/L), no positive effect on exercise response was shown.
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