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 increasing research interest (1, 3).

The rationale for this approach is that adequate carbohydrate should be consumed to support the quality of training sessions. However, we should avoid over-consuming carbohydrates on easier, less demanding days, as this may blunt the signals that lead to positive adaptive responses (2). Carbohydrates and fats are the body’s primary fuels....

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 low in carbohydrates – less than 50 grams per day or so – we can enter ketosis or increase the circulating concentration of ketones in the blood. That’s why these diets are called ‘ketogenic’ (5, 6). In some instances, such diets are known a “therapeutic ketogenic diets” due to the positive effects they have had on chronic...

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 carbohydrate ingestion at rates above 90 grams per hour accelerates muscle glycogen depletion and impairs performance (3, 4).

In this blog, inspired by an engaging Twitter thread authored by Prof. Tim Noakes and Iñigo San Millán, I'll delve into the metabolic outcome of ingesting 120 grams of carbohydrates per hour. Through this exploration, I aim to reinforce the...

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 ‘hitting the wall’.

Given that having a robust capacity to make use of fat stores during exercise is important, I quantify it in the lab with the athletes I work with. We can measure fat oxidation rates during exercise using a technique called indirect calorimetry, which involves the collection of expired air, and we typically do this across a range of exercise intensities in...

  @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) accumulating a substantial overall training volume and (ii) engaging in long, tempo runs on hilly terrain. Your training program emphasizes low-intensity sessions below the lactate threshold, allowing you to train extensively and frequently without inducing excessive fatigue (7, 8). The only sessions in your plan that exceed the lactate threshold are (i) a midweek trainer workout involving 8-minute...

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 daily lives. Jan had evolved into not just a athlete I work with professionally, but a close friend. The thought of the daily interactions coming to an end was a strange feeling, although true friendships are enduring.

My collaboration with Jan began during my tenure with Rowing New Zealand as the Head of Performance Physiology. The connection emerged after Eric Murray, a 2-time Olympic Gold...

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.

We published a study last year that found an ~10% reduction in power output at the first ventilatory threshold (VT₁) following 150 min of moderate-intensity cycling (9). VT₁ is used as a marker of the transition between moderate and heavy intensity exercise. I use it as the upper boundary of “Zone 2”, and encourage my athletes to perform the bulk of...

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 all athletes have regular access to laboratory facilities for physiological profiling assessments and the determination of thresholds. For those athletes, power profiling represents an alternative, field-based method that can be used to provide anchor points in our training programming. Also, power profiling may be used to provide a still-elusive ‘durability’ metric. In...

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 we have fat, stored in fat cells and in muscle. The rate at which we use carbohydrates and fats to support metabolism changes with things like exercise intensity and duration (14, 17), heat stress (6), and recent diet (2, 16). As our carbohydrate stores are relatively modest, we can become carbohydrate-depleted, and fatigued as a result, after exercise of sufficiently demanding intensity and...

I recently made a post on Instagram that got a lot of attention and questions, and it was one that compared the percentage efficiency of carbohydrate (CHO) ingestion when was taking 120 g of CHO per hour. There were a lot of questions, and of course it’s hard to explain in enough detail via an Instagram story (see below).

So, as such, in this blog, I am going to have a look at the emerging literature suggesting it may be possible to ingest carbohydrate at rates as high as 120 grams per hour during exercise (that’s ~5-6 gels!). Carbohydrate ingestion during training and racing has a long history in exercise physiology, sports nutrition, and endurance sport. Despite decades of research investigating the optimum dose, type, and form of carbohydrate to support performance, research is still emerging that challenges our practices. So, let’s get into it.

Why carbohydrate during exercise?

We have often discussed how whilst the body’s fat energy stores are vast and...