busted arm

I just got a cast on my left arm and was wondering what i could do to maintain fitness. the cast is short enough to allow me to ride aero bars so i was thinking of just throwing the bike on a trainer and using the aero bars. I was worried the sweat might make the cast lining rot. It is a fiber glass cast and almost looks like it has holes everywhere (it was made from this cloth stuff). beside from that, what could i do in the gym? i can't lift anything so i think i need to focus on core strength. Any ideas besides the normal situps, back raises? thanks.
-ryan

I have had numerous casts in my day. I haven't tried to get on a bike with them, but I used to play soccer with one on. As for the sweat rotting it out? Well you will sweat in that thing regardless and it will smell bad. So if you think balance isn't an issue then give it a try. Assuming that you don't have super sensitive skin you might be able to slip a fabric softener sheet under the cast edge and it might help things smell better.