This is a simple and very easy way to release your hamstrings. I believe it works on the same principles as ART (Active Release Technique) and the idea comes from a great book I am reading called "The Permanent Pain Cure" by Ming Chew. I have found when I do this correctly my hamstrings are much looser which creates much more free movement in my hips as well as getting rid of tightness in my lower back.
The first thing you have to do is to sit on the edge of a table where your feet can dangle below you. Sit back and place the tennis ball a bit behind your knee and under your hamstring. Sit back a bit and rest on your hands. Put a small bit of pressure down onto your hamstring. Now point your toes and slowly straighten your leg.
When you get your leg fully extended pull your toes back towards you. Then while you keep your knee straight, start leaning forward. Tighten up your thigh and hold the position for a couple of seconds. You can do this a leg motions a couple of times depending on how tight you feel.
Then move the ball a bit higher and again do the release, repeating as necessary. Keep moving the ball slowly up your hamsting until you get to your butt. I also move the ball to the inner and outer parts of my hamsting and do the release where I feel I am tight. I also use a harder rubber ball (or even a baseball) at times when I do the release. Go gently at first however.
After I raced on Sunday my whole body felt off on the left side. I did one back spinal stretch to get a point where I had a crick in my mid-back and did the hamstring release on the left hamstring. That was all I needed to get out of the discomfort I was in. I am still playing around with this and other releases from the Ming Method book and trying to experiment to see what effect each stretch or release has on my body. I do know that when I get these correct (as well as the resistance stretching) my legs feel like they are loosely hanging from my hips rather than feeling jammed or tight into the hips.
If you like the release you can find the instructions for this and other releases in the "The Permanent Pain Cure" book that explains the Ming Method. The quadriceps release is wonderful as well as the ITB release. I haven't found instructions like this in any other book. The releases are only a very tiny bit of the book as the rest has to do with how to stretch your fascia as well as well as other information as I reviewed here.