The bone structure in your hands will increase in density the more you punch. The muscles that stabilize your arm will also improve. After a few weeks, you will be able to punch much longer. I reccomend buying some sort of protection for your arms as you have just started practicing, however.

basically what tyler said STAY RELAXED...ill give you a example write a short letter with a pencil with your hand tensed for 2 minutes notice how the hand starts aching...now do the same thing relaxed as you would normally write, notice the difference? the pain your getting is most likely from that! your NOT relaxed...and lastly work on your technique that could be the second reason. For help with this watch:

http://www.youtube.com/watch?v=DUC8Z2d4t... <<
RELAX & TECHNIQUE

You need to relax when punching, being too tight is why you are feeling pain in in forearms

Then you are weak, do snooker instead

Well, don't do it then.

ok, so my forearm hurts when i hit the heavy bag, i've recently bought it and i've only been on it for a total of something like 2 minutes, but my forearm hurts when i hit it and i noticed after hitting it i have little red spots on my forearm, should i keep hitting it and will i get used to it? or is there something wrong,am i perhaps not punching it right?