Fueling for your race


This article is written more specifically for fueling for a marathon but the information can be applied to any event or race.

Effective preparation for any event requires careful consideration and planning of many factors.  Specific training, cross-training, sleep, recovery, tapering, race strategy and of course, nutrition, all play essential roles in executing on the day.  Ask any experienced athlete and they will say the right fueling, eaten in the right quantities and at the right times, can make or break your success.  Many first-time marathoners—and even seasoned marathoners—struggle with nailing down what to eat to make it through long training runs and executing on race day.  This article explains how to dial in your fueling for your marathon to make it the best one yet!

All movement requires energy.  The body requires fuel to create this energy.  This form of fuel comes in 3 types – Carbohydrates, Proteins and Fats.  Carbs are easily and quickly broken down to provide energy, and the most readily available source in the body as it is stored in the muscles, liver and blood.  Fat is stored throughout our body subcutaneously (on the surface) and viscerally (on the inside around our organs and in body cells).  Although we (all) have an endless store of fat in our body to fuel many many hours of activity, it is not as simple to access this source, as it is the carbohydrates, and is generally only used when working at lower intensity levels.  Protein is stored in the muscles and is a relatively negligible source of fuel for the most part.  We do not want to use protein as a fuel source as it is this that helps build and develop stronger muscle cells.  Protein is generally only used to provide energy if we do not have enough carbs available and we’re unable to access the fat stores due to the intensity we’re exercising at.

Therefore when it comes to athletic performance carbohydrates are our number one source of fuel.  However, we only have a limited available source of carbs stored in our body – a max. of approximately 2-3 hours at any one time for low intensity exercise, and that is assuming your stores are well topped up to start with.  The higher the intensity of movement the greater the energy requirements and therefore the shorter the duration those stored carbs will last for.

When training and racing beyond an hour it is recommended that you’re replacing some of this fuel that you’re burning to keep your stores topped up.  If exercising for long periods without replacing fuel effectively the body begins to break down muscle tissue (catabolize) to provide energy for the required movement, which is counterproductive.  During a race or training run, once you ‘hit the wall’, it’s difficult—both physically and mentally—to recover, so it’s important that you fuel up well before you start and keep your stores topped up throughout.

The amount of carbohydrates required during exercise depends on the intensity and duration of the activity, the fitness level of the participant and their metabolic predisposition to carbohydrate and fat metabolism.

We recommend that you try to replace 60% of the carbohydrate that you burn while you are training and racing. This is most often in the range of 20-40 grams of carbs every 30 min, but can vary considerably for any individual.  The exact rate of carbohydrate use can be individually determined during the VO2 portion of an assessment at the Peak Centre for Human Performance.

For the most part it is best to use liquids or gels during training as they tend to cause fewer gastrointestinal problems than solid food. However, when training for periods that are longer than 180 minutes you may need a little solid food.  Experiment with various combinations in training to find what works best for you so that you’re executing rather than experimenting on race day.  You don’t want any ‘surprises’ on race day with fuel that your body isn’t used to.  Treat race day like a training run, and you’ll have the best race ever!

Good luck!

Written by Lewis Morrison
M.SC Sports Science
Director of Sports Science

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