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Should I be doing ‘fasted’ rides like the pros?

Training without carbs could make you a more efficient rider. Illustration: Will Haywood

Michael Donlevy
18 Dec 2020

When people talk about fasted rides they’re referring to riding first thing in the morning without eating breakfast and limiting food (but not fluid) intake during the ride. This is a fasted ride in its most basic sense. However, personally I refer to this as training with low glycogen rather than ‘fasted rides’. Low-glycogen training can be done at any time of the day.

First up, some science: glycogen, which comes from carbohydrate, is the body’s main source of fuel for exercise at any intensity above 70% of your maximum. Restricting it requires the body to use stored fat for fuel, which makes you more efficient. More on that later.

In terms of timing, you eat as normal but have a lower-carbohydrate meal the night before and ride in the morning after consuming some caffeine and 25-30g of protein for breakfast. This preserves muscle mass while riding with lower glycogen levels.

Another option is to eat normally the night before, have breakfast, do your high-intensity training in the morning and withhold carbs for the rest of the day by eating protein and fats. You can then ride with lower glycogen in the evening if you’re training twice a day.

In terms of what to eat to ensure your glycogen is low, a good example would be a portion of fish or meat with two or three portions of vegetables and a side salad. The general rule is that to get the most benefit from this type of training you should avoid a really high-carb lunch or dinner before trying to train fasted the following morning, as your glycogen levels will still be too high.

The key is to not overdo it on the bike. To get the most out of low-glycogen training your rides must be zone 1 or 2 (out of 5, so 60-80% of your maximum heart rate where zone 5 is a 100% sprint) and personally I wouldn’t recommend intervals or riding at above 70%.

So what’s the point? The idea is to maximise fuel utilisation at a muscular level. From a scientific perspective, this is referred to as enhancing the mitochondrial (or cellular) adaptations in our muscles, which means they become more efficient at using fats as a fuel during endurance exercise.

If you can spare carbohydrate oxidation – the process of converting carbs into energy – during low to moderate-intensity exercise you’ll have more of it when you need it towards the end of a race when the intensity ramps up. In layman’s terms we’re trying to increase the mpg of our engine.

There are two potential drawbacks: firstly, the fact that you can’t (or shouldn’t) perform high-intensity training, and secondly the fact that you may compromise immune function. That’s because carbohydrate, particularly glucose, is the main fuel for immune cells.

But think about that engine analogy again and it’s clear why the pros do it. They want to maximise fat utilisation during low and moderate-intensity exercise to preserve glycogen for when they really need it. And this is nothing new – the pros have been doing this type of training for a long time.

Professional riders do, of course, have nutritionists and doctors to analyse every facet of performance and measure out their nutrient intake, but most riders will benefit from training with low glycogen, especially in the off-season when you’re racking up the miles. Just bear in mind that everyone is different and there may be a process of trial and error before you get it right.

The more efficient your muscles become, the better your performance – and there isn’t a single endurance athlete who won’t like the sound of that.

The expert: Dr Mayur Ranchordas is a reader in nutrition and exercise metabolism at Sheffield Hallam University. He is also a performance nutrition consultant who works with Premier League football players and referees, professional cyclists and triathletes

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