We have discussed in detail that having a robust capacity to use our fat energy stores to support exercise is important for long-distance triathlons. That is because our stored fat is effectively unlimited in the context of exercise, even very long-duration exercise in very lean athletes. In contrast, our stored carbohydrate reserves are finite and will be depleted to very low concentrations after exercise of sufficient length and intensity. To put this in perspective, a lean, 70-kg triathlete with 10% body fat has at least enough energy in their 7 kg of stored fat to complete more than Ironman triathlons back-to-back (3). Of course, those are theoretical Ironmans; the point I am making here is that whilst depletion of stored carbohydrates can lead to the fatigue we recognise as ‘hitting the wall’, we don’t slow down in an Ironman because we run out of fat energy (4).

As an exercise physiologist working in applied practice, I regularly test the fat oxidation...

_{Photo credit AsiaTri}

By Ed Maunder and Dan Plews

Straight off the back of some great racing at this weekend's 70.3 Vietnam Asia-Pacific Champs, we thought it was high time for another blog post. Some epic racing from some of our athletes last week, and greatly deserved. Berks taking second to current back-to-back World Ironman Champ Patrick Lange, and Assad Attimimi and Merle Talviste taking age-group wins (& 2nd spots in the age-group overall).

In the previous two blogs we talked about our paper in Sports Medicine last year where we made estimates of fat and carbohydrate utilisation rates during Ironman Triathlon at different performance standards (8, 9, and 13-h finishing times). We also published the spreadsheet we used to do this online, where individual athletes and practitioners could plug in their own measured values from laboratory assessments to enable more precise estimates.

However, we understand that many individuals do not have access to the...