Picture 2: This pose shouldn't be a pose, nevertheless it shows much more how it goes to bend forward than the picture on top. The legs are stretched. Muscles can be engaged and they are supposed to be engaged. The upper body lengthens. I look forward towards the direction in which I want to go. Bandhas? It cannot be seen if I engage them or not. Surely I do! Haha. The back is straight. Feet do not fall to the sides sloppily. Practicing that way the hip movements enlarge.
When the legs are engaged the hamstrings can be stretched safely. I do not make an attempt to reach the feet which could mean to stretch the shoulder forward. The shoulders remain down in almost every asana. The chest remains open.
A good question: When I practice an asana I ask myself of the goal of that asana. Where must I feel this discomfort that can be felt when I approach my limits.
Paschimottanasana strenghtens the legs and bandhas, it enlarges the movement of the hips, it lengthens the back side of the legs (hamstrings). It makes modest.
The benefits of this forward bending asana: It's good for the inner organs. It allows to relax the spine from the upright position.
Seeing myself on pictures helps to adjust myself. I think I'm often between the too extremes: totally sloppy or perfect. I engage my legs, but I want to fold my hands in front of the legs. This might cause a rounded back (not like in picture 1, but yes, rounded). I will check it again next time when I take pictures.
And here the master Mr Iyengar himself:
What is true for paschimottanasana is true for every pose. It's so easy to betray oneself, but then we're likely to remain the same, not so much will improve.
Strength, flexibility, endurance, concentration, modesty, daily practice, fun, focus..........yoga related notions.