Most people measure their flexibility by the length of their Hamstrings. Have you ever heard people say "I can (or cannot) reach my toes."
I also see many people stretch their hamstrings by bending forward (as in the photo). In my humble opinion as a yoga therapist, it's not a good way to do it.
The reason it's not a great way to stretch your hamstrings is because you are mostly going to be stretching your lower back, which does not need to be stretched. Bending forward can aggravate and de-stabilize your Sacro-Iliac joint by loosening the SI ligaments.
The best way to stretch the hamstrings is to isolate them, either in a supine (on your back) position with a strap or against a doorway, or standing with your back in neutral, as in the two photos below.
There are 3 hamstrings:
All of them flex the knee and extend your leg backward.
So...Should You Stretch Your Hamstrings?
Yes. Absolutely. Short hamstrings will limit your range of movement and comfort, and may tear when stretched without warmup.
But more importantly, we should strengthen the hamstrings. They are postural stabilizers - helping us stand upright. If weak, hamstrings can cause instability in our spine.
In addition, strong hamstrings don't need to work as hard. They are less likely to get injured when playing sports. Strong hamstrings can relax and recover faster.
Does massage help tight hamstrings?
Absolutely. As one of my teachers used to say:"If you can twang it (as a string), then you can tweat it." (transl. "treat it")