Exogenous Ketosis during Early Acclimatization at High Altitude: Ventilatory, Cardiovascular and Muscular Responses...

Exogenous ketosis, induced via ketone monoester (KE) ingestion, can attenuate blood desaturation and muscle deoxygenation during hypoxic exercise. However, its effect(s) on exercise capacity and underlying integrated physiological responses to incremental exercise to exhaustion during early acclimatization at terrestrial high altitude remain unexplored.

Healthy active adults were randomized to an intermittent exogenous ketosis (IEK; n = 16) or placebo (PLA, n = 17) group, before performing two incremental cycling tests to volitional exhaustion. The first was conducted at sea level (295 m) without prior supplementation. The second was conducted at high altitude (3375 m) after ~69 h of acclimatization, during which participants intermittently ingested KE (IEK) or placebo (PLA). During exercise, gas exchange, cardiac output, and both blood and muscle oxygenation were recorded continuously using a metabolic cart, transthoracic impedance, earlobe oximetry and near-infrared spectroscopy, respectively.

Preexercise blood ketone concentrations were higher in IEK than PLA (~2.1 mM vs ~0.3 mM, P < 0.001). However, both experimental groups exhibited comparable ( P = 0.525-0.644) high altitude-induced reductions in peak power output ( P < 0.001), as well as in blood ( P < 0.001) and muscle oxygenation ( P < 0.001) during maximal exercise and submaximal power levels. Furthermore, high altitude significantly increased resting and/or exercising ventilation ( P < 0.001) and cardiac output ( P < 0.001), yet irrespective of the KE versus placebo ingestion ( P = 0.529-0.828).

These findings indicate that intermittent exogenous ketosis during early acclimatization does not mitigate altitude- and exercise-induced reductions in blood and muscle oxygenation. Moreover, it does not importantly modulate ventilatory and cardiac output responses, and therefore does not seem to confer ergogenic advantage during subacute high altitude exposures.