LAB | KETONES IN PERFORMANCE CYCLING
There has been growing attention in cycling around a class of compounds called ketones. They have reportedly been used in the peloton successfully by teams to help give their athletes an edge. Though currently these ketones are exceptionally expensive, running into £1000s for a rider for a race, as the production is streamlined and scaled-up, nutritional products that contain a source of the ketones are to become one of the most sought after products for those who compete in endurance events over the next few years. They are reported to improve time to exhaustion and power at lactate threshold; so how do they work?
WHAT ARE THEY?
These compounds are formed naturally in the body during a state called ketosis, which occurs when the body becomes depleted of carbohydrates. Ketosis is a survival mechanism to produce sugar-like molecules from fat because the brain can not use fat itself as a fuel. (Some readers may be aware of ketogenic diets, and raspberry ketone, to help with weight loss; from a performance standpoint, going ketogenic is a very bad idea, as is any chronically low-carbohydrate diet.)
There are normally two main fuel sources that the body consumes during exercise: carbohydrates and fats. There are several differences in the oxidation of these two substrates:
– The metabolism of carbohydrate is more O2 efficient; i.e. it requires less oxygen to get 1 molecule of ATP (the compound that directly supplies muscles with energy) from carbohydrate than it does fat. This is partly why at near threshold – as O2 becomes limited – the body primarily uses glucose as the fuel source.
– The body’s storage of carbohydrate is extremely limited (1800 – 2400 kcal in trained athletes) compared to the practically unlimited supply of fat (40,000 kcal!)
Glycolysis, shown simplified in the scheme below, initially produces two molecules of pyruvate in the cell. Pyruvate is a precursor to Acetyl-CoA, which is the substrate required for the Kreb’s cycle – the pathway of aerobic ATP production.
Pyruvate in the cell, however, exists in equilibrium with lactate. The concentration of lactate is dependent on the concentration of pyruvate, which itself is dependent on rate of glycolysis within the cell. That is to say – the greater the use of glucose as a fuel, the greater the concentration of lactate.
HOW DO KETONES IMPROVE PERFORMANCE?
In a phrase – lower lactate.
Oxidation of carbohydrates always increases levels of lactate, even under aerobic conditions. A greater reliance on carbohydrates increases the production of muscle-fatiguing metabolites that over time leads to muscular fatigue and a decrease in muscular efficiency.
It is advantageous to burn fats as a fuel source at sub-threshold intensities as it spares carbohydrate stores for race-winning efforts, and also reduces muscular fatigue caused by metabolites. These ketones are a fuel source that are as O2 efficient as glucose, also, crucially, they do not lead to higher levels of lactate.
When one takes these ketones as a fuel supplement they can expect to be able to ride at a higher power for a given intramuscular lactate concentration, have a higher lactate threshold and also be able to ride at a constant power for a longer duration.
The beauty of this supplementation is that the body’s cells already have the machinery to utilize this fuel source, as it uses the same transporters as lactate. Athletes who are able to ride at high rates of glycolysis are able to do so because their body is able to transport lactate across cell membranes at high rates to be metabolized elsewhere. Since these compounds uses the same transporters, those athletes who are able to operate at high levels of glycolysis will likely see a greater performance benefit.
The key insight here is being able to create high concentrations of the ketones in the blood without requiring to be in the survival state of ketosis. The utilization of these compounds allow for a higher power at lactate threshold as well as time to exhaustion. At the moment the supplement is very expensive and not cost-effective for anyone but professional athletes. However, with greater demand and greater manufacturing volumes the price will fall hugely.