Marathon des Sables is a looong race, so staying healthy throughout the race is critical to finishing. And this starts as soon as training starts.
Training starts with making sure all the body parts work OK. Make sure your core is strong, as that is anchor for all movement. Make sure there are no muscle imbalances, and that you are flexible where needed and taut like a spring where needed. Make sure the legs are strong, as endurance running involves much more than aerobic endurance.
The pictures show a trip to the physical therapist at LOFitt. They've done a great job of addressing my biomechanical weaknesses, made apparent via two chronic ankle injuries and a knee problem all caused by my running. The pictures below show the analysis of my gait, which lead to corrective measures.