Just one thing to add for greenstiles - 'cos often people have this fecked-up perspective of how to get the best out of using a heavy bag.
It should be heavy that it can take some shots, and not be wildly swinging around, but not too heavy that it doesn't move.
And it's not there just to totally unload on - especially at first, anyways - your hands and wrists need to get used to the trauma.
Using a heavy bag is about there being some movement of the bag, some movement in you, and putting together punches in an effective way. So focus more on timing rather than trying to beat the thing to death. Move with it, but don't let it dominate you.
Your blows should sound a certain way - kinda snappy, not dull thuds.
It should be heavy that it can take some shots, and not be wildly swinging around, but not too heavy that it doesn't move.
And it's not there just to totally unload on - especially at first, anyways - your hands and wrists need to get used to the trauma.
Using a heavy bag is about there being some movement of the bag, some movement in you, and putting together punches in an effective way. So focus more on timing rather than trying to beat the thing to death. Move with it, but don't let it dominate you.
Your blows should sound a certain way - kinda snappy, not dull thuds.