What can you not do with a broken arm?

Restrictions. A lot depends upon the location, degree, level of instability, effectiveness of treatment. You really need to get specific guidelines from your treating provider...But i always mention when asked that using a jackhammer and repelling down a steep mountain are probably out for most.
Move. When one has a broken arm, in order to let it heal, it gets immobilized, that is it is placed at rest in order to let the bones heal. So, movement is not recommended. Once it's out of cast, it may be used gradually increasing resistance as it gets stronger.