A beginner’s guide to fuelling runs

Dr James Morton is the Senior Sports Nutritionist for Science in Sport (SiS), the leaders in endurance nutrition. He has led and collaborated in over 40 research papers and publications and is also Senior Lecturer in Exercise Metabolism & Nutrition at Liverpool John Moores University (LJMU).

For those new to running, it can be an overwhelming experience from a nutritional perspective. With an ever-increasing amount of fad diets and a growing list of sports supplement companies all recommending the latest race winning product, it can be hard for the beginner to really know where to begin when learning how to fuel your runs. In this post, Dr James Morton will return to the very basics of sports nutrition by ensuring you get the most from your training and races – hydration and carbohydrate of course!

Hydration Requirements

During moderate to intense exercise, we may produce 1-2 litres of sweat per hour depending on the exact environmental conditions. Although the production of sweat is a beneficial response as it is our body’s main way of losing heat and keeping our body temperature regulated, if such fluid losses are not replaced at appropriate rates dehydration occurs and performance can be impaired. Indeed, dehydration can alter the function of our most important organs such as the brain, the heart and the muscles themselves.  In a dehydrated state, our body temperature rises, our heart rate increases, we deplete carbohydrate stores quicker and we perceive the exercise to be more intense. In essence, we have to work so much harder just to run at the same speed.

The first strategy to offset the negative effects of dehydration is to therefore ensure you actually commence training or racing in a hydrated state in the first instance. We should aim to consume at least 5-7 ml of fluid per kg body mass (for a 70 kg person this can equate to around 500 ml) at approximately 3 hours prior to exercise.  This time-scale should allow your urine output and colour to return to normal (e.g. pale straw colour) prior to exercise. Consuming drinks that contain electrolytes such as sodium, like SiS GO Hydro are superior to plain water as they help the body to retain the ingested fluid. If this time-scale is not practical (such as an early morning training run), then we should attempt to hydrate the evening before by consuming electrolyte drinks with our evening meal (and also perhaps an hour or two before bed) followed by a small glass upon waking. 

It is difficult to provide exact fluid recommendations during the exercise itself given that hydration requirements are dependent on exercise intensity, duration and ambient temperature as well as individual characteristics such as training status, age and gender etc.  Nevertheless, traditional guidelines advise a drinking strategy that prevents dehydration equating to > 2-4% loss in body mass. In practice, such a drinking strategy usually equates to 500-800 ml per hour and depending on the environmental conditions, your thirst will likely determine if your body requires more. In order to promote re-hydration post-exercise, you get into the habit of weighing yourself before and after exercise and for every 1 kg lost during exercise, you should consume 1.5 L of an electrolyte solution.

Carbohydrate Requirements

The importance of carbohydrates in fuelling moderate to high-intensity exercise has been long recognised by sports scientists. Similar to hydration, the initial key to fuelling your runs is to actually ensure you commence exercise having consumed a carbohydrate rich meal approximately 2 hours before exercise. Failure to do so may mean your training intensity can markedly suffer, and this is especially important for the beginner. When it comes to fuelling during your runs, carbohydrate gels have now become runners’ preference given that they are easily digestible, provide a rapid supply of carbohydrate and of course, are easy to carry as opposed to carrying carbohydrate drinks.

For maximal training intensity (i.e. where speed is the main goal such as that required during intervals) and fuelling longer duration runs (e.g. 60-120 minutes), our muscles can utilise 60 grams of additional carbohydrate per hour, the equivalent of one gel every 20 minutes. However, it is important to note that not all runs require the consumption of carbohydrate during exercise. Indeed, if your run is of moderate intensity and duration (e.g. 30-45 minutes), then simply consuming your carbohydrate pre-exercise meal will be more than enough to get you through.

For those who take up running to lose weight, consuming additional carbohydrate during exercise can be the worst thing you could do as it can suppress ‘fat burning’ and prevent the very aim of your exercise in the first instance. The key is to tailor your nutrition to your running goals. 

Dr James Morton is the Senior Sports Nutritionist for Science in Sport (SiS). You can find out more about SiS’s endurance nutrition products on www.scienceinsport.com.