Optimizing your fuel intake may seem complicated (and sometimes it is) but learning the basics is surprisingly simple and worth the effort. In this article, Dr Jeroen Swart explains the basics of fuelling.
Dr Jeroen Swart is a sports physician and exercise scientist based at the Sports Science Institute in Newlands, Cape Town and the University of Cape Town Division of Exercise Science & Sports Medicine.
In addition to a medical degree, he is a specialist in Sports Medicine and has a PhD in exercise science. He currently divides his time between research, clinical sports medicine and high-performance cycling.
In 2019 he was appointed the Medical Director for UAE Team Emirates World Tour Cycling where he oversees the health of the team members and in addition provides expertise in biomechanics, nutrition and training load monitoring.
Why do you need to fuel up before your ride?
The reason we eat before a race or a hard ride is to replenish our liver glycogen stores which we then use to fuel our exercise and other normal activities like our brain’s processes during exercise. While we sleep the body’s blood glucose concentration is kept in a normal range by releasing glucose from the liver. So we eat to top this up before we head to the race or a hard ride.
What should you eat?
Since you don’t want food in the stomach or small intestine when you start racing or pushing hard, choose an easily digestible food source. If you don’t, you might experience nausea or even vomiting as your stomach’s blood flow gets diverted to your muscles and skin (which aids cooling) when you start to push hard. Whilst muesli, uncooked oats, nuts and seeds might be good for your health when you’re not on the bike they can take up to 12 hours to digest and are therefore not the right meal to fuel on unless you are doing a stage race in which case you are eating for the stages to come as well. The golden rule is to stick to something that will be digested and absorbed quickly. As an example, try eat about 2 slices of white bread, toasted or plain, with jam or honey. Avoid peanut butter or other oily foods. You could also add a banana and 500ml of energy drink. Another option would be a bowl of pasta but you want to skimp on the meat as this slows down the digestion process. Always remember to eat at least 90min before your ride. If you experience anxiety before a race you should try to reduce the amount you are eating and eat earlier – before the race nerves set in.
Once you start pedaling
You want to consume some carbohydrates during your warm-up, or shortly before the start of a race. This will move some fuel from your gut and into your blood. If you don’t do this, you are going to tap into the glycogen stores in your liver and muscles to fuel the exercise and since there is only enough of this around to last for approximately 90 minutes of strenuous exercise, you may end up experiencing the dreaded bonk. The key is to get the fuel moving into your blood via your gut before you start riding.
Maltodextrine vs. Fructose – what should you eat?
Carbohydrates The problem with sugars is that they are very sweet. Drinking enough sugar to fuel your exercise will be sickeningly sweet and won’t quench your thirst. Drinks with a lot of sugar will be unpalatable, especially during hot conditions. They also have very high osmolality (high molecule to water ratio). This delays the emptying of the stomach contents and their absorption. High osmolality drinks can also cause nausea and stomach upsets.
Maltodextrins are short chains of glucose molecules that are easy to digest and therefore are available almost as rapidly as sugars. Despite being composed of sugars, they are not sweet. They are also less osmotically active as each chain acts as a single molecule despite being composed of a long chain of sugars. They, therefore, empty from the stomach quickly and cause less stomach upsets.
Fructose is a sugar that cannot be used by muscles. To be of any use it first has to be delivered to the liver where it is converted to glucose in a process called gluconeogenesis. The glucose is then transported to the muscle where it is used. However, fructose is transported across the gut wall through it’s own transporter (GLUT-5) while the other sugars compete for limited transporters (S-GLUT-1). Drinks, gels and bars with a mix of glucose and fructose can increase the rate of carbohydrate absorption by 50% in comparison to drinking or eating glucose or maltodextrin only. Mixing these different sugars results in the optimal formulation for rapid absorption, fuelling your body during hard racing and training whilst preventing nausea or other gut problems. These mixes are called “multiple transportable carbohydrates” and are often a 2:1 mixture of maltodextrin and fructose.
How much is enough?
How much carbohydrate you need depends on the exercise duration. Your mouth has receptors that sense the intake of carbohydrates, reduces your level of perceived exertion and then improves your performance. This means that even during shorter races there is a benefit to ingesting carbohydrates. As a rule of thumb, the longer the duration of the race, the greater the rate of carbohydrate ingestion should be. For races longer than 2 hours you should aim to ingest at least 60-90g per hour. Some recent studies show that up to 120g per hour can be absorbed but you can only do this with multiple transportable carbohydrates and only if you have “trained” your gut by eating or drinking a similar rate during training sessions.
About adding protein to your fuel
Adding a small amount of protein, (approximately 10-15% to energy drinks) will improve your performance in your next session. So this is only useful in stage races or during really hard training weeks.
The practical solution
For shorter races you should drink 250-500mls per hour of a commercial energy drink that contains multiple transportable carbohydrates and is mixed to a solution of 8%. So that’s 8g of carbohydrate per 100ml of drink. You can easily calculate this by dividing the carbohydrate per serving by the amount of fluid in 100ml increments. If it is hot and you feel like drinking more, then try up to 600mls per hour or otherwise drink a little water. Do not drink too much as you cannot absorb it all and the excess fluid will just weigh you down. TIP: If it is very hot, rather than drinking more try pouring a little bit of water over your head, back and legs to cool you down.
For longer races you should drink 500mls of the same mix as detailed above but increase your carbohydrate intake with bars and gels. The maximum quantity per hour is 120g though and be sure you have ‘trained’ your body to handle this high and intake of carbohydrates before the race. If you start to feel hungry, eat an energy bar or some other easily digestible but more solid form of food.