The bonk has ended more Alpine days than any climb. Two-thirds of the way round, a long way from base, the power drains away and every gentle rise becomes a wall. It’s not a fitness failure. It’s a fuelling one, and it’s completely avoidable.
Here’s how to fuel a big mountain day. The day before, on the bike, and afterwards, because in the mountains recovery is just fuelling for tomorrow.
The maths of the bonk
Your body stores enough glycogen for roughly 90 minutes to two hours of hard riding. A big Alpine day asks for several times that. The gap between what you store and what you burn has to come through your jersey pockets and your bottles, and it has to go in steadily, because your gut can only absorb so much an hour.
One more piece of maths. Hunger runs about half an hour behind your actual needs. By the time you feel hungry on a climb, you’re already in debt, and on a mountain, it’s very hard to eat your way back out. You fuel to stay ahead, never to catch up.
Start the day before
Pre-loading isn’t one heroic bowl of pasta at ten o’clock the night before. It’s carbohydrate with every meal the day before. Normal portions, familiar food. Rice, pasta, potatoes, bread. You’re topping up the tank, not force-feeding it.
On the morning, eat breakfast two to three hours before you ride, built around carbs you know agree with you. Porridge, bread and jam, whatever you’ve trained on. A big day is no time to experiment.
On the bike: 60 to 90 grams of carbohydrate an hour
That’s the working range for most riders on a long, hard day. Start eating in the first half hour, before you feel like it, and keep it regular. A little every 20 to 30 minutes beats a lot every two hours.
What 60 to 90 grams actually looks like:
| Item | Carbs, roughly |
|---|---|
| Banana | 25 g |
| Energy gel | 20 to 25 g |
| Cereal or energy bar | 30 to 40 g |
| 500 ml bottle of energy drink | 30 to 40 g |
| Small pastry from a village bakery | 30 to 40 g |
The easiest way to hit the number is to spread it across sources. Carbs in your bottles doing quiet work in the background. Real food early in the day while your stomach is happy. Simpler sugars later, when it isn’t. Above about 60 grams an hour your gut needs mixed sugar types to absorb it all, which is exactly what most modern sports drinks and gels are. And nothing new on the big day. Test everything on a training ride first.
Fuel the mountain, not the clock
Here’s what flat-land fuelling advice misses. On a flat ride you can eat whenever the clock says. On a mountain day, the terrain decides for you, and you have to plan around it.
You can’t eat on a descent. Twenty to thirty minutes of hairpins needs both hands and all of your concentration, and it’s cold. So top up near the top of every climb, in the last easy stretch or at the col itself, and put a layer on while you’re at it. The summit is your last call before half an hour of no eating.
The valleys between climbs are your kitchen. That’s where you eat properly, refill the bottles and reset for the next col.
And drink on the climbs, because that’s where you sweat hardest, even when the air feels cool. Aim for 500 to 750 ml an hour, more in real heat, with electrolytes on hot days. Village fountains will keep you topped up. Most are drinkable unless signed “eau non potable”.
Recovery is tomorrow’s fuelling
A one-day ride ends at the finish line. A mountain week doesn’t. Day four’s legs are decided at day three’s dinner table.
In the first half hour after the ride, get carbs and some protein in. It doesn’t need to be scientific. A recovery drink, or a sandwich and a yoghurt, does the job. Then a proper dinner with carbs you’d be happy to ride on, and sleep. Skip the recovery window once and you’ll get away with it. Skip it three days running and day four will collect.
How we plan it
Fuelling is part of every morning plan on our trips, alongside the route and the weather. We work out where the climbs fall, where you’ll eat, where the water stops are, and what to carry, so the plan matches the mountain rather than the clock. Coaches carry spares for the rider who’s miscounted, and the evening review catches the fuelling mistakes before they compound into day four. Plan, ride, review.
Keep reading
How to pace a long Alpine climb is the other half of not blowing up, and your first Alpine col: what to expect puts both to work. For the bigger picture, and how to choose the right Alpine base for your level, see Cycling in the French Alps.
Plan your trip
On our coached weeks the fuelling plan is built into every day, and by the end of the week you can build your own. Get in touch and we’ll point you at the right trip for your riding.