The inverted reach stretch is a functional movement that you should add to a dynamic warm-up routine, especially when your workout is going to involve a lot of leg muscles. It stretches out the hamstrings and also activates the core and stabilizer muscles in your legs. You can stand in one position holding the inverted reach, and you can also make it more active by taking steps in between each pose.
To do the inverted reach stretch, bend over under control as you stick one straight leg out behind you. Your chest and leg should be parallel with the ground as you balance on your other leg. You can either reach your arms directly over your head, or reach down to your toes. Reaching overhead will make the exercise slightly more difficult, but it does cause more activation of the core muscles in your back.
You should feel a stretch in your hamstrings as your stabilizer muscles and core muscles tense up to keep stable.