You leave through larch forest, soft underfoot and quiet. Then the trees thin out. The meadows open, the paths narrow, and the Alps start to stack up in front of you. Old irrigation channels, the bisses of the Valais, run beside the trail, water sliding down the mountainside toward the valley. Higher up the ground turns to rock and scree, and the glaciers around Mont Fort, at 3,328 metres, appear on the skyline.

Some mornings the cloud sits on the ridge and you run inside it. Other days the sky is blue and you can see for what feels like a hundred kilometres. Either way, the hut is hours away, and the only plan that works is the one you packed.

Eat for the climb.

The first hour is easy. By the third, it isn't. This is where the Performance Bar goes to work. Rhubarb & Vanilla, 33g carbohydrates, 217 kcal, 55g, made with premium oats, pure honey, freeze-dried rhubarb and natural vanilla. Soft enough to chew with cold hands, small enough to forget it's in your pocket until you need it.

Eat one before the start, mid-climb, or at the top.

Drink for the distance.

Up here the air is thin and dry, and the miles between water points are long. Fill a soft flask with Vitargo + Electrolytes: our proprietary carbohydrate with sodium, potassium, calcium and magnesium, in Citrus or Grapes.