WHO THIS IS FOR
IS THIS YOU?
The rider whose intervals fall apart in the final reps
You start strong but cannot hold target power by the last two or three intervals, and you suspect fuelling rather than fitness.
The weight-conscious cyclist riding intervals fasted
You skip pre-session food to keep calories down and wonder why your hard sessions feel harder than they should.
THE ROADMAN VIEW
The Roadman view
Intervals are where fitness is built, and they are the worst possible place to be on empty. Anthony's own under-versus-optimal fuelling experiment made this concrete — when he ran the same sessions under-fuelled, the power numbers were worse and the sessions felt worse. The adaptation you are chasing comes from the quality of the work intervals, so half-fuelling them is sabotaging the very thing you got on the bike to do.
The mistake usually comes from a good intention gone wrong: trying to lose weight by riding hard sessions fasted. It backfires twice. You hit lower power, so the training stimulus shrinks, and you tend to overeat later because you are running on empty. Dr Sam Impey has made the case repeatedly — fuel for the work required means the hard work gets the fuel, and the deficit, if you want one, comes from the easy days instead.
Get the timing right and intervals transform. A carbohydrate-rich meal one to three hours before tops the tank, a small top-up just before sharpens the start, and 60g an hour during anything over about 75 minutes keeps the last reps as strong as the first. The good news is this is simple and repeatable — a bowl of oats and a banana beforehand, a gel or two during, and your hardest sessions land the way they are supposed to.
EXPERT EVIDENCE
WHAT THE EXPERTS SAY
- Dr Sam ImpeyWorld Tour nutritionist
High-intensity sessions are the priority for carbohydrate fuelling, not the place to restrict. Glycogen availability directly limits the power you can produce in intervals, and the quality of those efforts determines the adaptation. Riders should arrive at hard sessions with topped-up stores and fuel through longer ones, reserving any energy restriction for low-intensity days.
Hear it: Why Pros' 120g Carb Rule Fails Amateurs | Roadman Cycling - Uri CarlsonRegistered dietitian nutritionist; fuelling specialist
A controlled comparison of under-fuelled, optimally fuelled, and over-fuelled riding showed the under-fuelled sessions consistently produced the lowest power and felt the hardest. For interval work specifically, arriving and riding fuelled is the difference between hitting target watts on every rep and fading through the set.
Hear it: Under vs Optimal vs Overfueling on the Bike | Roadman Cycling Podcast
PRACTICAL APPLICATION
DO THIS WEEK
Top up carbs 1–3 hours before
Eat 1–2g/kg of carbohydrate in the window before the session — for a 75kg rider, 75–150g. Oats and banana, toast and honey, or rice the night before plus a light pre-ride snack. Keep it low in fat and fibre so it sits easily before hard efforts.
Add a fast carb just before the first interval
A gel or a few chews 10–15 minutes before the work starts sharpens the opening efforts, especially for shorter morning sessions where you could not eat a full meal. It tops blood glucose without sitting heavy in the stomach.
Fuel through sessions over 75 minutes at 60g/hr
For longer interval blocks — over-unders, sweet spot sets, or VO2 work with a long warm-up and cool-down — take 60g of carbohydrate per hour as drink mix, gels, or chews. This keeps the final intervals as strong as the first rather than fading on fumes.
COMMON MISTAKES
WHAT CYCLISTS GET WRONG
MISTAKERiding hard intervals fasted to save calories.
FIXUnder-fuelling lowers interval power and shrinks the adaptation. Fuel the hard session fully and take any deficit from easy days and off-bike meals.
MISTAKEEating nothing during long interval sessions.
FIXAnything over 75 minutes needs 60g of carbs per hour. Without it, the last intervals collapse and the most valuable part of the session is lost.
MISTAKEEating a high-fat, high-fibre meal right before intervals.
FIXHeavy, fatty, or fibrous food sits in the gut and causes discomfort at intensity. Choose low-fibre, low-fat carbs in the pre-session window.
FAQ
FREQUENTLY ASKED QUESTIONS
Should I do intervals fasted to burn more fat?
What should I eat before an interval session?
Do I need carbs during a one-hour interval session?
Can I drink my carbs during intervals instead of eating?
What if I train intervals first thing in the morning?
Does under-fuelling intervals affect recovery too?
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