Other than eating right, what are some ways to stay in shape/be healthy while wearing a cast?

I broke my left arm (I’m right-handed, thankfully here), and it stinks in one sense because I was starting to get involved with yoga and maintaining a good weight. Now I’m mired in grad school papers and other life happenings without a surefire way to burn off the extra energy. I’ll have the cast on for another month. Woe is me, woe woe is me.