Flexibility has been venerated and even worshipped
in the yoga world. In fact, one of the main reasons that people say they can't do yoga is because they're "not flexible."
As yoga teaching and practice becomes more biomechanically informed, we see that extreme flexibility is a body imbalance that has serious repercussions in
one's ability to maintain movement efficiency and body delight in daily life.
Pop quiz: which one of these portrays sufficient hamstring flexibility?
See below for the answer!
The "science of stretching" is currently being studied and articulated by some wonderful teachers (listed below). I've sourced from some of them and have been incorporating three main ideas in my recent classes:
Only go into poses/movements that you can get into and out of with your own muscles. That means not using your arms to lever your legs into "hip openings," not grinding yourself deeper into twists with your elbows, not using straps or other props to increase your backbends or open your shoulders. Remember that range of motion is determined by your nervous system/brain and when you override where you can go with your own muscles, your nervous system will perceive that as unsafe territory and resist the stretch.
At the end range of your movement, engage your muscles. Never hangunsupported in yoga poses, such as standing forward bends (unless your knees are bent and you are releasing your back). As Jules Mitchell says, "strength and optimal muscle function" at the new range of motion enables your nervous system to "work in cooperation" with movement.
Increase range of motion and allow the body to re-pattern with restorative yoga. Supporting every part of the body with props and the floor allows time forthe nervous system to accommodate a new way of being. Try including a few restorative poses into your practice and see if your body finds its way to a happier equilibrium.
Bottom line: you can live a really good life without putting your foot behind your head!