Intrarace Fuel: The science of fuel, part 2.

So we’ve briefly discussed the evidence surrounding the ‘best’ way to consume nutrition surrounding a race or ride, but let’s get in to the nitty gritty of the best way to maintain a sustained output during an event, or as I like to call it, the best way to keep shoveling coal into your internal furnace. 

If you’re seriously looking to plan your diet for an event, then you need to be very clear about the event you’re competing in. Unfortunately I am unable to provide specific advice regarding this, but what I can do is attempt to provide you with the tools to help you optimise your nutrition.

In this article, we’ll exclude ultra-endurance events, as that is truly another article in itself. Ultra-endurance is generally defined as an event of greater than 6 hours duration. Therefore,  we’ll discuss the evidence surrounding events less than that.

The role of carbohydrates in endurance events is well established (1, 2), and is known to delay time to fatigue, with one study demonstrating an increase in maximal duration of exercise of up to  17% over 2 hours in trained cyclists, where fatigue is defined as a reduction in Vo2 of greater than 10%(1). But what’s the best way to consume carbohydrates during an event?

Does it matter how long you’re competing for? And in what form should you consume the glucose?

We’ve previously addressed the topic of glycaemic index and its role in the selection in pre-race nutrition, but its role in intra-event nutrition is less clearly defined. I wasn’t able to find any studies comparing the outcomes of carbohydrates of varying glycaemic indices. My belief is that  this is because of the prevailing belief that during an event, your aim is to replenish energy as quickly as possible, and physiologically, this makes sense. You need to get the sugars into your bloodstream as quickly as possible for it to be available as energy.  Whilst not specifically addressing this, a study from the early 90’s found the ability to maintain exertion across multiple bouts in rapid succession was significantly increased by oral carbohydrate replacement, and maximally by intravenous replacement, which almost instantly raises blood glucose levels when compared to glucose absorbed via the gastro-intestinal tract. (1)  Therefore we can extrapolate that regular consumption of rapid acting carbohydrates is the optimal method through which an athlete can maintain output when compared to sporadic consumption of longer acting carbohydrates. Unless of course you can find an event that will let you hook up a drip.

So you should be regularly consuming rapid acting carbohydrates throughout your race, but how much, and how regularly? Well in an event of less than 60 minutes (1), supplementation is less likely to be of significant benefit, but between 1 and 4 hours you can prolong your ability to maximally exercise by supplementation. Physiologically, we’re aiming for a state known as euglycemia, or a blood glucose level of between 3 and 7. Now, you’re unlikely to be wearing a subcutaneous blood glucose monitor during an event, but when considering cycling, the rate of glucose ingestion of approximately 1g/hour appears to be the optimal rate to delay fatigue. In the real world, this equates to a standard gel, such as an SIS isotonic Go Gel every 22- 30 minutes. Obviously, this is only a guide to get you started. You’ll need to titrate your own needs depending on your efforts and your own body habits.

It’s important to note that maintaining your blood glucose levels consistently throughout exercise is vital, as provision of a rescue dose of carbohydrates post fatigue, was far less effective at allowing for prolonged exercise when compared to athletes who regularly consumed carbohydrates to prevent fatigue. 

Finally, in what form should you consume these carbohydrates? Fluids, gels or bars? Well, the most important is consuming the correct amounts of energy during the event, so whichever form is most agreeable to you is the form I would recommend. However we must also consider the fact that athletes are often dehydrated in endurance events.  Electrolyte drinks are known to increase ad libitum (drinking when you want to) drinking during exercise, which helps maintain your fluid volume thereby preventing dehydration. Additionally, gastric emptying is delayed with solids when compared to gels and liquids, so theoretically, you’ll experience a more rapid onset of action when compared to energy bars.

So in conclusion, in an event over 60 minutes, you should certainly be consuming carbohydrates throughout, and any combination of fluids, gels or solids totalling 60 grams per hour will help you squeeze the most performance out of your body as possible!   So why not find some gels you like and get prepped for your next big event! 

What’s your favourite way to fuel for a big ride? Let us know in the comments below!

As always, leave any questions in the comments and I’ll do my best to answer them! 

By Dr Tim Davis – Pushys Resident Medical Expert.

Sources & References 

  • 1 – Coggan AR, Coyle EF. Carbohydrate ingestion during prolonged exercise: effects on metabolism and performance. Exerc Sport Sci Rev. 1991 Jan 1;19(1):1-40.

2 – Papadopoulou SK, Xyla EE, Methenitis S, Feidantsis KG, Kotsis Y, Pagkalos IG, Hassapidou MN. Nutrition strategies before and during ultra‐endurance event: A significant gap between science and practice. Scandinavian Journal of Medicine & Science in Sports. 2018 Mar;28(3):881-92

Categories: Nutrition

Tagged as: , ,

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s