Exogenous ketosis increases blood and muscle oxygenation but not performance during exercise in hypoxia

Fourteen highly trained male cyclists completed a simulated race of 3-hour intermittent cycling, a 15-minute time trial and an all-out sprint, with inspired oxygen fraction gradually lowered from 18.6 to 14.5 percent. In a randomized crossover design they received 75 g ketone ester, 300 mg/kg bicarbonate, both, or a control drink, in addition to 60 g of carbohydrate per hour. Ketone ester counteracted the hypoxia-induced drop in blood and muscle oxygenation by about 3 percent, whereas bicarbonate decreased blood oxygenation by about 2 percent without affecting muscle oxygenation. Time trial and sprint performance were similar across all conditions.