The hamstrings attach to and help support your pelvis. When you sit in a chair, they are taken out of the picture, so your back muscles have to hold your torso up. Especially if you end up slumped over, your back muscles will be working from a long position, while your hamstrings will be in a short position since your knees are bent, your pelvis is tilted down, and they are squished against the seat of the chair.
Muscles are like Goldilocks: they like their fibers not too long or too short, but just the right length for maximum contracting capability. So you can help both your back and hamstrings by giving them opportunities to work at their preferred lengths.
Since the back muscles are already long in this situation, there’s no need to strive for greater length by stretching them. Therefore, more benefit can come from focusing on lengthening the hamstrings and keeping the back muscles in a more neutral working position.
The backs of the legs are a pretty common place for people to stretch, but often when we bend over to touch our toes, we end up rounding our backs. However, we can get more from the stretch if we keep our backs flat–keeping the back muscles neutral and putting more of the lengthening action on the hamstrings. You can also think of it as sticking out your tailbone. If you don’t often practice bending with a flat back, it can be useful to have a mirror nearby to make sure you are doing what you think you are doing, especially since it can feel odd to stick your butt out like that.
For this first stretch, stand with your feet hips width apart and bend down toward your toes as far as you can without rounding your back. Imagine your hips are big hinges and you want to keep the movement isolated to the rotation of these hinges. Try to keep your knees straight, even if it means you don’t bend very far at all. Remember, the goal isn’t to touch your toes, but to stretch your hamstrings. So there’s no reason to cheat by moving other body parts just so you can reach further to the floor.
Lying on the ground is another way to keep your back flat. Using a strap, belt, or towel, pull your leg up slowly. This stretch is quite different because your hamstrings aren’t also busy helping you stand while they are being stretched. Make sure you keep the bottom leg resting completely flat against the floor.
Change things up by putting your heel up on a fence, table, or other structure at the right height for you and lean toward your leg. Keep both feet facing forward, but feel free to change the angle of your leg relative to your body in order to stretch different muscle fibers.
Notice that this person’s back is rounded, not flat. It’s fine to stretch with a rounded back, but know that you won’t be targeting the hamstrings as much. Try doing both to feel the difference in the stretch. It’s great to have a variety of ways to stretch so you’re not always lengthening the same muscle fibers.
As usual: stretch slowly, as long as feels appropriate to you, and do both sides, even if only one side is bothering you.
It makes a big difference to stretch these muscles when they are warm. You can go on a walk with your dog first, or stretch them after a run, some laps in a pool, playing tag with your kids, or after a bike ride.