Science versus Reality.
An article I wrote in Issue two of "Ultra Magazine"
The ultra-runner is a unique breed. So unique in fact, that very little research exists on specific fuelling strategies for powering your performance mile after mile after extreme mile. The main aim of an ultra runner is to maintain a high-energy output over a prolonged period of time, sometimes over multiple days. The average runner burns anywhere between 600 to 1000kcals per hour! This means paying as close attention to nutrition and hydration as you do to race strategy, as failure to do so can scupper your chances of success. Being a sports dietitian and ultra runner, my experience of both worlds has shown me, that at times the science does not always hold true over these crazy distances. So what is the science and what do we find really works?
It is well-documented, that the primary cause of fatigue during exercise of longer than 60 minutes is depletion of energy stores. Energy comes in the form of calories from carbohydrate (CHO), fat and protein. Out of the three, CHO is more readily converted into energy and hence is the body’s preferred energy source. But herein lies the problem; we only have enough stored CHO to last 90 minutes of exercise, compared to fat, where stores are thought to be able to fuel a runner for at least 1300kms! This may explain the growing trend of ultra endurance athletes surviving on low CHO diets in an attempt to maximize fat oxidation to fuel their runs. When you think of it in this light, it may make sense but one should not ignore the endless number of studies that prove CHO taken during prolonged exercise increases time to exhaustion. US ultra runner Timothy Olsen (winner of Western state 100) is famous for maintaining a low CHO, high fat diet around his heavy training schedule. However, even he trains with CHO, and although not much (3-5 hour runs he has 1-2 gels) every little helps. A study in the Journal of Medicine, Science, Sport and Exercise (2004) showed that even a mouth rinse with CHO drink (without swallowing) improved cycling performance during a 1-hour time trial by 2-3%! So let’s have a look at just how much CHO you can absorb out on the trails for hours on end. The “Gold Standard” for CHO consumption during exercise is approximately 60g per hour (based on the ability of 1g/min CHO absorption) with a maximum possible absorption of 90g/hour if taken in a 2:1 blend of glucose:fructose (known as dual CHO ). This combination increases absorption rate over time, resulting in very high oxidation rates. Many ultra runners like to ingest protein alongside CHO’s during races. A review in the Journal of Sports Medicine (2014) concluded that although protein ingestion during prolonged exercise may inhibit muscle protein breakdown, it does not further enhance performance capacity when compared to the ingestion of ample amounts of CHO alone.
So we are clear on the science that it is possible to absorb between 60-90g CHO over the hour and protein ingestion alongside CHO’s won’t necessarily improve our race performance but how does this translate into reality? Tolerating 90g of CHO per hour is not for the weak stomached, especially over races lasting longer than 3 hours! Not many of us can tolerate 4 gels, or 2 energy bars every hour for 12 hours. Not only is it tough on the stomach but also taste fatigue will set in pretty early and the logistics of carrying 24 energy bars in our back-pack over 100miles would be a challenge in itself. The reality of it is, during ultras we need to survive and to survive we need to be flexible. If you aim to consume 30-60g of CHO an hour, you will find yourself in a strong position. Unless you are among the elite few, speed is not of the essence but keeping one foot in front of the other is the aim of the game. If you go slowly enough, for long enough, its gets to the point where you can use anything for fuel, just so long you take in the calories and your stomach can tolerate it. Early on you in the race can survive on gels and other CHO’s but after 4 hours taste fatigue can set in and your body starts craving more. Although, unlikely to improve performance, adding one part protein to four part carbs may keep hunger at bay (protein takes longer to digest) and may provide some “comfort” six hours into a long race. This can be in the form of energy bars or real food such as peanut butter and jam sandwich. Marc Laithwaite, event organizer of the Lakeland 100 says “in our experience, most runners can’t follow traditional sports nutrition advice of gels and drinks. They reach a point where they can’t stomach their usual food choice, so our aim is to offer a wide range of foods such as sandwiches, soup, jelly babies, cake, hot drinks and cola at every check point. Later on in the race, runners will often choose things they have never considered before, so advice is to get used to eating anything and everything because you won’t know how you are going to feel later on in the race”. Ed Catmur is an experienced Ultra runner and still admits to finding nutrition a struggle! He has an impressive strategy for racing over 50km and manages up to 100g per hour of CHO from energy bars and chews! But over these distances one must always expect the unexpected as Ed did running the Las Vegas 100 in Spring this year. The hot climate meant he had to drink a lot and this was not something he was used to. This led to stomach cramps and he was unable to eat anything at all for the full 100miles. He still finished though, as an ultra runner, he’s made of tough stuff.
So where does this leave us? The answer is, listen to the science and plan what you can but be flexible as no matter what the science says you are more constrained by what you stomach dictates. Over such immense distances, no matter how well you have practiced your nutrition in training, things change. It’s a good idea to get used to sports products, such as gels, sports drinks and bars as they are portable and provide neat energy in small volumes. You will need real food though, therefore take items such as bananas, pretzels, peanut butter sandwiches (cut up into bite size pieces) or homemade flapjack on your training runs to get used to variety. The most important note is that, just like you, sports nutrition is very individual. What one runner can tolerate, the next can’t. Be flexible, experiment in training and be open to changes on the day...most important of all, listen to your body and not just the science.