Your legs won’t feel it until a few hours in, but your head will notice sooner: this is a day for easing yourself in. From Saint-Jean-Pied-de-Port you walk into the hills of the Basque Country. It goes up and down, but never gets really wild. You climb around 500 metres, spread across the day, and you get used to it surprisingly quickly.
The descents are the hardest part. There is more downhill than uphill, so your knees will let you know about it, especially towards the end. You are on your feet for almost 7 hours, so feel free to take a proper break along the way. Bidarray is your reward: rucksack off, boots off, feet up.
First day, take it easy. The Camino isn’t going anywhere.