Life drawing: yoga poses with Nina

I'm still focusing on line drawing so I once again decided to leave the Conte crayons and stick to using charcoal pencils and graphite pencils.
Nina began with a series of two-minute poses in different yoga positions, which created some interesting shapes, especially with feet appearing in unexpected positions... It was a good exercise in trying to capture overall shapes very quickly.

Then came two poses of 10 minutes:

This final drawing took 25 minutes, using a 4B pencil. The model was facing away from me with here elbows leaning on a small stool (hidden from view) and her hands in a praying position. Due to restrictions of space, I had to do this one from a standing position holding the sketchpad in my hand.

I though the shape of the model's back, the visible line of her spine, and the upturned soles of her feet,  would have made this a good pose to draw, but for some reason, I don't think it really comes off at all well. I'm not sure quite why, but I just wasn't on form....

Second life drawing with Robin

I last drew Robin back in May 2013, when I attended my first life-drawing class, so I was hoping to see some improvements in the intervening seven months. I'm not too sure the drawings actually demonstrate that.

I'm trying to focus on line at the moment, as that is what is required for part of my next assignment on my OCA drawing course. I therefore steered away from the Conte crayons and went back to pencils and charcoal pencils as my main media.

We began with a series of short 10-minute poses where Robin played imaginary musical instruments.
Here is the flute:

The legs are too short and the hand indistinct, but I was quite pleased with the effect of smudging the charcoal pencil to get some shading.
Here is the violin:

I think the hands are slightly better here.

Finally, we did a 40-minute pose, with Robin holding a broom:

Again, I think the legs look slightly too short and rather weedy compared to the body, but I'm not unhappy wiht the line of the face and also the way hands rest on the end of the handle.
Is there an improvement on last May? Maybe a little...