You can not be restricted from any type of activity if you are not on active duty. Outside of your drill weekend and your active training you can do pretty much whatever you choose, with the exception of illegal narcotics. (even that is kinda a gray area, you may be ok to do them, but if you show up for duty with any traces in your body you are in trouble, so that is what they really get you for)
I regularly engage in many activities with a "high risk" of injury, and the unit knows about it, no problems. If I get hurt and cannot preform my duties from that point on, then I'm out, thats all.
Basicly, if you are not getting a paycheck for that day, they have no legal authority to order you to do anything.