Many of my sports nutrition clients have committed to a marathon in the Spring and with that comes a schedule of races building up to the main event. This can include a 10-miler or half-marathon and some races shorter than that. I am often asked about the best fuel before a longer training session or race.
Traditionally sports nutrition has focused on macronutrient intake, which involves consuming the correct amounts of fats, proteins and carbohydrates. The appropriate macronutrient balance is crucial to optimal performance but what must also be considered is nutrient timing, which was developed by Ivy and Portman . This focuses on not only what to eat, but also when is the best time to consume nutrients in the training cycle.
They explain that in any training program there are periods when the muscle is actively involved in producing energy, periods when it is recovering and periods when it is growing.
Each of these operations requires different types of nutrients and if you’re able to deliver the right nutrient mixture to the muscles at the right time you can greatly enhance recovery from exercise and improve muscle growth, strength and power.
Water is probably your most essential nutrient; the effects of dehydration are quickly felt. If you are feeling thirsty you may be slightly dehydrated as the thirst mechanism is thought to kick in when we’ve lost just 1-2% of water .
Even mild dehydration can lead to fatigue and even when just 1% of bodily fluids are lost, your temperature can increase and your performance can be affected. Exercise performance is impaired when a person is dehydrated by as little as 2% of body weight . Cell hydration may contribute to muscle cramps and impaired recovery . Fatigue towards the end of a prolonged sporting event may result as much from dehydration as from fuel depletion.
The best indicator of your hydration levels is the colour of your urine; it should be pale and straw coloured. Make sure you start your race or training session well-hydrated and that you have fluid available during the session.
And don’t forget the electroytes which are lost via sweating; these include sodium, potassium, calcium and magnesium. Potassium and sodium are needed for optimal cellular hydration and muscle nerve function.
Magnesium is involved in many processes that affect muscle function including oxygen uptake and energy production . It is a common electrolyte deficiency and can contribute to muscle weakness and cramps or spasms. Coconut water, diluted fruit juices and vegetable juices provide a good variety of nutrients and electrolytes.
General guidelines for fluid intake pre-event are:
- 400-600ml (or 5-7ml per kilogram of body weight) of fluid approximately 2-4 hours before the start to normalise total body water volume and return urine output to normal.
- Drink 5-8ml per kilogram of body weight 10-20 minutes before you start running; this can include carbs or a gel
Gastrointestinal distress is what every runner aims to avoid before a race or training session, so a balanced meal before a training session is not a good idea. You’re aiming for maintaining even blood sugar levels to prevent any hypoglycemia after the start of the race. Ideally you will need to wait at least one to two hours before you run after consuming a larger meal. This will give your body time to digest and avoid and any intestinal discomfort.
Focus on foods that you know you can digest easily. Try and avoid any fibrous or fatty food that may cause gastrointestinal distress, but make sure you fuelled well the evening before. An alternative solution is to focus on a smaller liquid meal (such as a nutrient dense smoothie) about 15 to 70 minutes before you exercise which is easier to digest.
If you can tolerate it 10-20g of high quality whey protein taken within an hour of your exercise (as part of a sports drink) can reduce the release of stress hormones during the exercise. This can be important for longer distance events where elevated stress hormones can exhaust your body quicker.
Make it personal
These are useful general principles, but it’s essential that you personalise them to your own preferences and training schedule. What works for one athlete doesn’t necessarily provide the best solution for the next athlete. And most important of all, practice in training what you are planning for your race; never try anything new on race day!
1. Ivy, J and Portman, R. 2004. Nutrient Timing. Laguna Beach, CA: Basic Health Publications.
2 -3. Casa, D.J. et al., 2000. National athletic trainers’ association position statement: fluid replacement for athletes. Journal of athletic training, 35(2): 212–24.
4. von Duvillard, S.P., Braun, W.A et al., 2004. Fluids and hydration in prolonged endurance performance. Nutrition. 20(7):651-656.
5. Nielsen, F.H and Lukaski, H.C. 2006. Update on the relationship between magnesium and exercise. Magnesium Research, 19(3):180-189.