A while back I was looking at a picture of my down dog with bent knees. Except I wasn't bending my knees, I thought they were completely straight. When I took this forward fold picture for this post I was trying my hardest to straighten those legs!! I began to notice that tight hamstrings were stopping me short in a lot of poses.
Enter foam roller (ps. This made me realize a lot of the tension in the back of my legs is in my calves),extra stretches after... workouts and A LOT of attention in my practice. I've been zeroing in on hamstrings in all of my poses.
If you feel like you could use a little length in your hamstrings try adding two blocks to your practice. In forward fold place hands on blocks outside feet and press into them to deepen your fold= lengthen your hamstrings. They can also add support so you can rock some weight up onto the balls of your feet for an even deeper stretch.
If I have some extra time in a fold, I'll step up onto both blocks with my toes slightly off the front so that I can shift my weight forward for a deeper stretch ( if your hands don't touch the floor use another block for support).