Français 
I have been always surprised by the number of sport athletes unaware of their own body anatomy.
To be councious of it, is a first and important step to prevent injury and help healing.
Some of our muscles have a major place in the whole balance in movement.
Some of them are working in absolutly all sports.
The principal hip flexor is one of them , the psoas, also intimatly linked by his vertebral insertions (T12 to L5) to your back !
This core stabilizing muscle located near the hip bone affect mobility, structural balance, joint function, flexibility and much more.
While walking, driving, even sitting at your desk for hours, you are using it.
By his size the psoas is one of the most vascularised musle of the body and can be a witness of your health. Very contracted sometimes ,it can be a sign of accumulation of too much toxins in the body.
Your osteopath can relax it at the practice , meanwhile you do need to take a daily care of it at home and learn how to strecth it.
So i invite you to discover it throught this 3D video link :
Also have a look of the following pictures and postures to learn how to stretch it. Remember to breathe deeply to get an efficient strecth . We have 2 psoas, one of each side of the body, so do alternate the front leg.
Stretching it daily you can forget of a lot of back issues !
