Sorry you folks are having a hard time dealing with chemo.
While your subject line states atrial fibrillation, AFib, I don't see that anywhere in your post.
If your husband has AFib and is able to control the heart rate to reasonable levels, light biking, walking, and curling should be possible from that point of health. I take Metoprolol to control/lower my HR due to AFib.
If your question about chemo and exercise I suggest you make your post at the cancer community:
http://www.medhelp.org/forums/show/59