I had really tight hamstrings. I have been stretching them for quite some time now and it improved remarkably.

When I look at [this picture][1] I notice the straight upper an lower back.

My problem is that my butt always tucks under when I squat (anterior pelvic tilt, "butt wink"). The same applies for the shown stretch. So, my idea was that both problems are somehow connected.

This is not a picture of me, but I look basically like [this][2] (except for being able to almost touch the ground with the palms of my hands):

But I can clearly feel that I compensate lacking flexibility with spine rounding.

So, is this still a hamstring problem or is it another muscle? Please give me specific stretches to achieve the position shown in the first picture.


  [1]: http://theaposition.com/golfproformance/wp-content/uploads/sites/63/2014/04/earth-touch.jpg
  [2]: http://www.jasonbarron.com/how-i-touched-my-toes-in-41-days/