Training and Planning six months out from Hawaii.

And so, it starts! Countdown to Kona!

Taking things easy with purpose!

Now at six months out from Hawaii I have just finished the season with solid hit out at Challenge Melbourne. This is the time the body and mind need to rest up and recover. While the time will come for the training to ramp up it’s not sustainable physically and psychologically to do this all year round. Well… for me anyway!

So, the plan for the next month or so is to take the foot off the accelerator and just keep a nice comfortable base of training without any intensity. However, there can be real purpose to this. This period of lower intensity work provides the ideal opportunity to not only recover but also to work on metabolic flexibility, a now trendy concept in the endurance world.

Fat Adaptation and Metabolic Flexibility

One of the key determinants of performance in Ironman Triathlon is energy availability, especially in the back end of the race. We have long considered ‘carbohydrates as king’ when supplying our bodies with fuel for exercise. Carbohydrates get converted to glycogen which in turn fuels our muscles when we exercise.

However, when it comes to relying on carbohydrate sources alone in endurance events there is one major concern. Running out!

There has been a lot of recent work in this area, led by Dr Dan Plews, who is not only a sports scientist and coach to some of the worlds best Ironman Triathletes but he, himself won the World Ironman Age Group Championships in Hawaii last year. Last year his team published work in the Journal of Sports Medicine that showed that most Ironman Athletes are absolutely going to run out of energy if they are expecting to rely on Carbohydrates alone.

My attempt to simply explain why;

We can think of our carbohydrate stores like a tank of fuel. Hopefully if you have loaded up a little in the day or two before a race the tank is full!

Once we start, the tank starts to steadily empty as our systems begin to use these stores. Carbohydrate oxidation occurs to generate energy. Much like an engine and a petrol tank!

This tank holds about enough energy to keep us going for a couple of hours. So of course, we need to top that tank up as we go; bars, gels, and other easily digestible carbohydrate sources.

The problem! Unfortunately, our bodies, or our stomachs can only process a maximum capacity of carbohydrates at a time. About 60-80 grams (240-320 cal) an hour and this tends to reduce as we get onto the run and our body is forced to shunt blood away from the stomach to more muscles and extremities to keep us cool.

But we are burning energy at a much higher rate than this (about 1000 cal/hour depending how hard we work). So our tank has a much bigger outlet than inlet, and modelling shows that it will end up empty about 4 hours into the bike and hitting the wall will follow !

Our solution! We need a second tank! And luckily, we all have one, and it’s pretty much bottomless! Our bodies Fat Stores. Like we can oxidise carbohydrates for energy we can also oxidise fat stores and they aren’t going to run out in a hurry.

How does this work? We know for most of us with lower intensity exercise we burn fat as a source of energy especially in the absence of carbohydrates. Metabolic testing can be done and shows exactly the composite of the fuel sources that we are burning as our intensity of exercise increases. General findings are that those athletes who have high carbohydrate diets and rely on higher levels of carbs during training have poor ability to utilise fats as fuel when tested.As the intensity of exercise rises, very quickly so does the proportion of carbohydrates they are metabolising and they begin entirely burning carbohydrates at suboptimal levels. A big problem as discussed earlier!

However, we do have the ability to adapt and change and become more efficient in burning fat by training our bodies to do so. The nature of Ironman training itself probably improves fat burning efficiency in some athletes to a degree, especially for those pro’s logging 30-40 hours of exercise a week. But current evidence provides an argument for being pro-active and systematically training our Metabolic Flexibility (ability to utilise both carbohydrates and fats as fuel) in order to maximise performance in endurance sport. Primarily this is achieved by restricting carbohydrate availability, forcing our bodies to get better at tapping into our fat stores for energy. One strategy is to include some fasted training into your program. Another strategy, as used by Dan Plews with his athletes is to lower the general carbohydrate content of the diet transitioning to a lower carb higher fat diet. This involves reducing the amount of carbohydrate we eat, ranging as low as 50 g per day to as high as 130 g (depending on the phase of adaptation). In doing so, we encourage the body to adapt in order to use fat instead of carbohydrate, which makes sense given we aren’t giving it much carbohydrate to use as fuel anymore. In Dan’s work (link provided with much more detail) when he retests athletes after this protocol there are large improvements in fat utilisation; in that the athletes can primarily use fat for fuel, and then continue to contribute fats to the mix, up to much higher exercise intensities. Hence the term Metabolic Flexibility. The desired result, two fuel sources and racing harder for longer.

Summary and Application.

I have operated myself on a lower carbohydrate approach for the last couple of years, cycling in and out of being quite strict and then quite liberal. The approach can be periodised or trained like physical training itself. I look at this period when my general training is low intensity as a time to train my metabolic system. I partly do it because I enjoy the science behind endurance sport and performance which means I am fascinated in testing these applications. When the training changes in dynamics it will be time to titrate carbs back in to fuel those higher-end sessions. Remember that at high intensities carbs remain king! And you need to fuel sessions appropriately, so nutrient timing is the major consideration. Consider the relevance of the session you have planned and how to get the most of that session. Make sure your coach is on board if you have one, so you can plan the process together. Starting out the adaptation process can be tough, with a slump in energy before your system adapts. This can take 4-6 weeks.

I also have great access to our dietitian at work to bounce ideas around with. I would highly recommend Lauren at Symmetry Physiotherapy Hoppers Crossing to anyone looking at nutrition for sports performance. She can steer you in the right direction, remembering that this approach is most relevant for a niche range of endurance sports working at lower intensity levels.

For anyone interested I highly recommend reading these blogs by Dr Dan Plews. He outlines the practical application of his work with an athlete.

Shay McLeod
Symmetry Physiotherapy