Ketone ester ingestion impairs exercise performance without impacting cognitive function or circulating EPO during acute hypoxic exposure

In a double-blind crossover design, 13 healthy male participants completed two 5.5-hour sessions at 4,000 m simulated altitude while receiving ketone ester or placebo. Tests included a graded exercise test after 1.5 hours and a submaximal bout after 3 hours, along with measures of oxygenation, ventilation, acid-base balance, cognitive function and blood erythropoietin. Ketone ester reduced power output in the graded test by 3.6 percent while blood and cerebral oxygenation were similar. It lowered blood pH, bicarbonate, pCO2 and glucose but did not affect cognitive function, and erythropoietin rose by about 56 percent after 5 hours in both conditions.