GR20 is an advanced hike, meaning full day treks with steep descents and challenging switchbacks. Although it is becoming more and more popular, it remains one of the most difficult treks in Europe. To overlook this could put inexperienced walkers in danger. Do not overestimate your skills, and prepare for the trip. The GR20 is for hikers in very good physical shape who already have the experience of high mountain trekking over several days. Keep in mind, the weather in summer can be hot and you’ll also be packing a daypack filled with water and other things you’ll need throughout the day.
It is recommended to do aerobic exercises at least 3 times a week. It is good to get in some hill walks on rough, uneven terrain, to build up ankle strength. Train to walk downhill, get used to knowing where to put your feet. Aim to progress walking downhill at a reasonable pace — two walking poles will reduce the shock on your legs.