This is a great “on the go” stretch. You can almost always find a bench, cable box or other structure to help you get into the stretch. The rotation in the torso gives you more bang for your buck because you get a spine stretch and a hamstring stretch. Two birds with one stone! This is also a great post-running or biking stretch since it can be done outdoors and doesn’t require any special equipment.
Stand facing the bench (wall, trashcan, or whatever you can find), and put one foot up. Make sure that your hips are squared to the front, and your toes point straight up to the sky. Stretching is 10 times more effective when it is done in proper alignment- take the 2 extra seconds to make sure you’re lined up correctly. Place your opposite hand on the outside of the thigh and turn your chest as you reach back through the opposite arm. Try to stay tall as you rotate so that you’re maintaining length in the spine- it will give you that much more of a stretch. The trick is to not let the hips rotate as you rotate your spine. If you’re right leg is extended forward, think of pulling back through the right hip in order to keep them square.
**Pro tip: make sure that whatever you put your foot on is below hip height, especially if you have tight hamstrings. Anything hip-height or above will make it impossible to keep the hips in alignment and could over-stretch the hamstring.