We have discussed at length in previous blogs how developing an advanced capacity to metabolise fat for fuel during exercise can be useful for long-distance triathletes. We’ve also published research on it; for example, one of our recent papers showed a relationship between an athlete’s peak fat oxidation rate (PFO) and performance in an endurance trial. The addition of PFO to traditional models of endurance – VO₂max, thresholds, and economy – improved the prediction of performance (16). Other labs have shown relationships between PFO and endurance, including Ironman performance (8). However, something I think is missing from the discussion is how having a robust ability to metabolise fat during training is helpful, specifically during high-volume days with multiple sessions. That will be the focus of this blog.

 Basics of carbohydrate metabolism

I feel like a bit of a broken record in this one, but during prolonged endurance exercise, we primarily use two fuels to support our metabo...