The flexibility is amazing and puts me to shame. My cycle looks like arse in comparison.
Ignoring my bruised ego, the arm movement is very nice! I promptly shoved it into Photoshop and brutally ripped it apart for the purposes of analysis.
I've done my best to identify where the key poses in the cycle are — not sure if I hit them 100% accurately but they seem to be roughly in the right place. Obviously there are differences in my cycle and this one — the torso here is much more flexible but in a way it's a good thing. Viewing a more exaggerated animation means it's much easier to examine how arms are following the body.
The contact poses are interesting because of the forearm placement. They're poised up and ready rather than lowered, as I'd been toying with, which I think was giving me problems as it was making things a bit 'busy.' It's also a nice pose in general — having the arms almost tensed like that gives a much more cautious look to the character. The wrists are very nice too!
As the character drops into the down position the torso moves forward and the elbow follows. The forearm relaxes very slightly and comes down.
As the body starts to rise again the forearm is brought closer to the chest and the elbow, again, starts to come back. The character rises into the 'up' position and the forearm again lowers very slightly.
The second contact is slightly further forward than the first one, to counter the leg.
As previously observed most of the shoulder movement seems to come from the twisting of the chest.
That diagram is a bit cluttered, so it's probably easier to see with the body:
Serves to give a better idea of the shoulder and elbow in relation to the body.
It seems to have been helpful, though now I'm worried I've mucked my cycle up completely and that this method won't work. It's certainly given me something to toy around with, though, which can only be a good thing.