The Impact of Exogenous Ketones on Athletic Performance: Counterintuitive Findings

Examining Ketone Supplements’ Impact on Athletic Performance

This study scrutinized contradictory evidence regarding the efficacy of exogenous ketone supplements, which have grown increasingly popular amongst athletes seeking a competitive boost.

Some prior investigations demonstrate ketone supplements canenhance performance by providing an alternative energy source. However, other studies conversely show no measurable benefits or even negative impacts on performance.

Ketones produced naturally by the liver act as an extremely efficient fuel for both the brain and muscles when carbohydrate availability drops, such as on a low-carb, high-fat ketogenic diet. Exogenous ketone supplements attempt to simulate this biological process without requiring strict dietary adherence to achieve ketosis.

Multiple hypothesized mechanisms exist for how ketone supplementation could improve aspects of athletic function. Ketones may offer an additional rapid energy substrate that gets utilized during intense exercise. They might also alter fuel utilization patterns, sparing glycogen and blood glucose while increasing free fatty acid oxidation. By providing extra fuel to power muscles and brain, as well as delaying carb depletion, ketones could plausibly extend endurance capacity.

This study set out to test those assumptions by investigating if ketone supplements truly enhance high-intensity cycling time trial performance relative to a visually identical placebo. The researchers recruited well-trained male endurance cyclists riding over 5 hours weekly and consistently demonstrating excellent conditioning maintenance.

To best simulate real-world race dynamics, athletes performed tests under ecologically valid conditions mirroring a cycling competition setting. This included preparations like pre-race fueling and warming up then completing a maximal 20-minute cycling time trial on their own bikes on Computrainers. That duration closely matches a 40 kilometer time trial event.

The singular difference across two identically structured trials was the supplement consumed as a drink 30 minutes before commencing each test. On one occasion cyclists drank a ketone ester providing around 500 milligrams of ketones, while for the other trial they ingested an indistinguishable non-caloric placebo. That double-blind design ensured neither participants nor researchers knew which supplement was administered until final data analysis.

Contrary to expectations, the study analysis showed cyclists’ average power output and pacing strategies declined following ketone intake compared to placebo. Those findings oppose initial hypotheses and some previous claims that available blood ketones offer performance synergies.

Expanding on prior observations of increased submaximal exercise oxygen demands with ketone utilization, researchers suggest ketones may heighten cardiorespiratory burden during high intensity activities. That could accelerate fatigue development through heightened aerobic strain when power outputs approach maximum capacities.

Further mechanistic and applied research should continue exploring these apparent performance discrepancies. Findings may have implications around fueling guidelines and race nutrition recommendations in events placing heavy emphasis on anaerobic metabolism. Clarifying optimal contexts for ketone use could maximize benefits while preventing any potential detriments.