It evolved from Methode Naturelle - an approach to physical conditioning that strove "to be strong to be useful".
Like Personal Defense, it is based on what comes naturally and what works. It also focuses on being able to respond to real life threats in a practical way.
You don't have to climb mountains to start. Just get up and take a walk. Run a bit - see how it feels! Instead of watching your kids at the park, climb up on the equipment yourself. If we are to defend ourselves and those around us from threat, we must be able to physically respond. More importantly, what good is defending a life if that life is only misery