Different training sessions require different fuelling methods. In this blog post I briefly explain what the body´s main fuelling source is during short high intensity interval training and provide a few fuelling tips for an interval session lasting 1-1,5 hours whether it is indoors or outside.
What is the main source of fuel during short & intense interval training?
During high intensity efforts the main source of fuel the body will use is carbohydrates. Carbohydrates are the fastest burnt energy source before fats and protein. Carbohydrates are stored as glycogen in the liver and muscle tissue if not used immediately as energy. Carbohydrates consumed during exercise are known as exogenous carbohydrates and can provide an extra fuelling source when glycogen stores are depleted.
Tips on fuelling for interval training:
1) Allow time for digestion
Makes sure to eat your main meal (e.g. breakfast or lunch) at least 2-3 hours before training. This gives you some time to digest your food properly so that you don´t feel bloated, heavy or sluggish and you shouldn´t experience acid reflux during your effort.
2) Have a pre-training snack
Having a small carbohydrate-rich snack of around 30g carbohydrates 30-60 minutes before your session provides an opportunity to help you feel energised. As your last main meal would have been 2-3 hours ago a small snack with carbohydrates and some protein will help to stablise blood sugar levels so that you don´t go into the session already feeling low and depleted.
This would also be essential for an early morning interval session when there is no time for breakfast before. Having a small carbohydrate-rich snack before getting dressed for maximal digestion time in the early morning can make a huge difference to your training performance.
Good examples include a banana with peanut or nut butter, slice of bread with cheese or a homemade rice cake.
3) Make sure to hydrate before
No matter the season, it is always best to go into a training session well hydrated. This helps to improve blood circulation, therefore, aiding muscle function and helps to normalise blood pressure during exercise. Hydrating before training is particularly important on very cold days, as many people battle to drink when it is ice cold and very hot days, as sweating is increased.
4) You won´t always need exogenous carboohydrates during a 1 hour interval session
Exogenous carbohydrates are foods and drinks high in carbohydrates such as gels, sports drinks and solid foods such as bananas or bars. Research shows mixed results whether exogenous carbohydrates provide additional improvements to performances lasting around 1 hour if a cyclist is in a fed state with high glycogen stores. This is mainly because your glycogen stores can usually provide the necessary energy to fuel the session but is not sufficient for durations > 1 hour (1) (2). However, it is clear that going into an interval session with depleted glycogen stores (i.e. overnight fasting), performance is improved with additional exogenous carbohydrates even during short sessions lasting 1 hour (2).
Knowing the research, it is also still important to listen to your body. You shouldn´t rely solely on research studies to fuel your body correctly, as they are often very structured and standardised and cannot take into acoount all the variables of your life. If you feel like you need additional carbohydrates during a short interval session then have them!
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References
Desbrow, B., Anderson, S., Barrett, J., Rao, E., & Hargreaves, M. (2004). Carbohydrate-electrolyte feedings and 1h time trial cycling performance. International Journal of Sport Nutrition and Exercise Metabolism, 14(5), 541–549.
Learsi, S. K., Ghiarone, T., Silva-Cavalcante, M. D., Andrade-Souza, V. A., Ataide-Silva, T., Bertuzzi, R., de Araujo, G. G., McConell, G., & Lima-Silva, A. E. (2019). Cycling time trial performance is improved by carbohydrate ingestion during exercise regardless of a fed or fasted state. Scandinavian journal of medicine & science in sports, 29(5), 651–662.