Endurance sport challenges many aspects of our physiology, not least our metabolism and our fuel stores. Our primary energy sources that broken down to power exercise are fat and carbohydrate (1). The body’s fat energy stores are vast and effectively limitless during exercise, while our carbohydrate energy stores – endogenous muscle and liver glycogen – can be depleted to low concentrations during prolonged, vigorous exercise (2–4). Therefore, a vast literature has emerged over the last ~100 years on the importance of our carbohydrate energy stores for endurance performance, and strategies to ..read more

With the athlete I coach, I promote what I call the “Right Fuel, Right Time” approach to nutrition for endurance training, as discussed in blogs and on our courses. By "Right Fuel, Right Time," I mean advocating for the timely management and adaptation of nutrition, particularly carbohydrate intake, according to training demands. These objectives may aim to maximize acute performance within the session or facilitate high rates of fat oxidation. In the literature, we come across the term "Periodised carbohydrate intake," which is an approach that follows a very similar principle and is seeing i ..read more

I have been reading and writing a lot about exogenous ketones recently. This is an exciting area of research, and I’m hearing great things from applied practice, too. There’s increasing evidence that exogenous ketone supplements may improve training outcomes (1–4). However, recently as I’m personally not training as much anymore, I have become interested in the use of exogenous ketones from a health perspective. The research is quite fascinating. In this blog, I’ll describe how they might have broader application to health, too. What are exogenous ketones? We know that by consuming a diet very ..read more

                            I wrote a blog about the recent research assessing the effects of ingesting carbohydrates at very high rates, >120 grams per hour, during endurance exercise (1, 2). My view of the literature, as discussed in the blog, is that there isn’t yet any compelling evidence that ingesting carbohydrates at these super high rates will improve long-distance triathlon performance, or that it’s worth the logistical hassle and risk of gastrointestinal upset. Indeed, there’s even some evidence that carbohydrat ..read more

?RookMediaProductions Fat oxidation, and fat oxidation rates get talked about a lot in the world of endurance sports and triathlon. Of course, being able to break down fats for use as fuel during prolonged exercise is an important determinant of performance in ultra-endurance events like Ironman. Our other fuel source – carbohydrates – are relatively limited and are depleted during prolonged or intense exercise. Being able to use fat effectively reduces the rate at which we burn through our carbohydrate stores, and thus delays the fatigue associated with depleted carbohydrate stores, or ‘hitti ..read more

 ? @rookproductionsmedia In recent blogs and newsletters, I have extensively discussed 'within-session intensity regulation.' I believe that proper within-session intensity regulation is one of the most critical components of the training process. It's a topic I spend a lot of time contemplating, planning for, and researching. But what exactly do I mean by 'within-session intensity regulation'? In this blog, I'll attempt to clarify this concept. Context Imagine you're training for an Ironman. You're currently in the midst of a four-week Specific Strength training block, focusing on (i) ac ..read more

On July 9th, 2023, Jan van Berkel, also known as "The Berklizer," triumphantly crossed the finish line at Ironman Switzerland, claiming 1st place. This race marked his final appearance as a professional triathlete, and as a coach, I can confidently say that witnessing this moment was one of the most emotional experiences I've ever had. From the exhilaration of his 4th race victory to the poignancy of concluding an almost 8-year coaching partnership, the range of emotions was remarkable. Coaches understand that, next to family, the professional athletes we guide hold a significant place in our ..read more

As readers of our blogs will know, I am involved in research with colleagues at AUT in New Zealand on ‘durability’. We defined durability as the time of onset and magnitude of deterioration in physiological profiling characteristics – such as the ventilatory and lactate thresholds that mark the boundaries between intensity domains – over time during prolonged exercise (4). More simply, physiologically and perceptually, a 300 W effort when 20 min into a session is not the same as a 300 W effort when 200 min into a session. An athlete’s durability refers to how big the effect of those 200 min is ..read more

In the triathlon and cycling communities, many of us have power meters on our bikes, or smart trainers at home. Power output data can be helpful in pacing efforts and tracking longer term progress. I myself programme many of my training sessions using power output – e.g. 4 x 40 min at 270 W for an Ironman workout – with the target number guided by the laboratory-based physiological profile of the athlete I am working with. For example, in the session above, the target power output is designed to be just above the first lactate threshold, in the so-called heavy intensity domain. However, not al ..read more

A thought-provoking review on low carbohydrate diets and substrate oxidation rates was recently published in the journal Frontiers in Physiology (10). The author list includes a couple of the big names in low carbohydrate research, Tim Noakes and Jeff Volek. In this blog, I will summarise some of the key messages and takeaways from the review. The traditional model of exercise and substrate oxidation During prolonged, endurance exercise, we primarily use two fuels to support our metabolism and keep us moving. We have carbohydrates, which are stored as glycogen in muscles and in the liver, and ..read more