I didn't say that there weren't any physical benefits to be gotten out of it, my main point is that boxing correctly is the is the most important part of the heavy bag. You forsake this in training and you're bound to make that mistake in the ring. Who's going to stand infront of you as you do a number on them? You have to train accordingly for a real opponent. If you want to improve your conditioning then you can always increase your intensity on the bag and still do everything for the right reasons