Funny you should mention Zazen. I just got back from a short work study at Tassajara Zen Mind Temple and it's rekindled my zazen practice somewhat. Although I'm far from diligent, I'm finding it's making me less argumentative at work, and that's a good thing, especially for my coworkers. Anyway, my wife was there to give massages to the students in exchange for her stay and commented that all the students were in really great physical shape overall. They all needed more massage work - that sleep deprivation is pretty hard on them. Their spines were very strong; she said it was like two solid cords on either side of the spinal cord, but they all seemed to hold a lot of tension in their arms, which she attributed to the posture of zazen. The students have a fairly rigorous practice there.
Anyway, my return to zazen got me thinking about yijinjing again, mostly because it's such a great compliment to zazen, and I've totally forgotten it. According to the dominent creation legend of yijinjing and xisuijing, Bodhidharma made it (and all of kung fu) just to help zazen practice. It occured to me how brilliant xisuijing is for exactly this purpose. I've never learned the sequence, only seen it described in books and vidoes, but the general format of seated calesthenics seems really good for zazen, perhaps even more appropriate than yoga, which is where many American Zen practitioners turn for help. Clearly, you need some practice to offset zazen. I'm thinking if I continue my zazen practice, I should pursue xisuijing more aggressively.
Here are some resources for you:
Xisuijing by Sh Guolin Yijinjing by Shi Guolin
Yijingjing by Shi Deqian
Yijinjing poster by Shi Deqian