If you're trying to increase the flexibility of your hamstrings, and you frequently stretch like this, you will get more out of your stretch if you focus on other parts of your body besides the hamstrings.
Unfortunately, for the unknowning dude in the photo, his form needs some work. Not much, but some.
Try this stretch in front of a large mirror, or with your teacher,. Most often, we think we have good form, only to learn that we've been doing something else completely and we weren't even aware of it!
First, stand with your feet hip width apart, parallel. Roll your spine down over your legs, with your arms dangling below. Stop when you feel as though you've reached your end point. When you look in the mirror, where are your hips?
If your hips are shooting back behind your legs, like in the photo, you need to move them.
They should be right up above the ankles, so your legs are perpendicular to the ground. I'll explain how to do this in a few paragraphs down below.
Where is your head? It should be dropped between your arms, following the shape of your spine- not like the photo. Don't allow the head to break the flow of energy in the stretch. If your head is lifted, your neck is shorten, which then translates to tension in the low back.
One good thing about the photo is that his knees are straight. Look in your mirror and check out your own knees. One thing you definitely do not want is for your knees to hyperextend, or lock backwards. Soften the knees so they're not locked, not very bent, but neutral.
Now, back to your hips. To shift the the hips forward, focus on your shins. Bring the weight of your shins forward, so the shins are perpendicular to your feet. You're ankle is now more flexed and non-resistant. When your shins come forward, your knees will also bend. This also puts equal weight in the soles of the feet, not just back in your heels (like in the photo).
Now, focus on your sitz bones. Keeping your shins right where they are, slowly spin the sitz bones upward, away from your heels. Your knees will begin to straighten a bit, and you'll start to hang forward further. You should now feel a true hamstring stretch.
The added bonus is that you can most likely now touch your toes, something you may have previously thought you could not do. Keep a slight abdominal connection the whole time, so you don't hang in your low back. And, of course, definitely do not bounce in this stretch!
Certain pilates exercises also stretch the hamstrings in the same way. Hamstring Stretch on the chair, is one obvious one. Push Through, Elephant, Spine Stretch Forward, and Ballet Stretches are all worth practicing to help increase hamstring flexibility!
Don't all these details seem complicated? If it sounds too confusing to figure out yourself, ask your pilates instructor or personal trainer to check out your Stretching Form and to give you a few pointers! Read more!