You could always ask your doctor, or even get a personal trainer. There are probably ways to make it work, even with a wrist that won't heal. A trainer might help you get started and "learn the ropes", or even working out with a friend who already works out on a regular basis at the gym. There is always hope, even at the "ripe" old age of 21 
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I'm 24 years old and live in WA State. I was diagnosed with Asperger's at 9. I received a BS in Psychology in 2011 and I intend to help people with Autistic Spectrum Disorders, either through research, application, or both. On the ?Pursuit of Aspieness?.