Hitting the speed bag...

[Snowfist]

Most people I see hitting the speed bag really wind back there hand almost behind their head. I can use the speed bag and get rhythm but i don't bring my fist back. My fist basically has a very short range of motion compared to others i've seen. Is this basically my 'style' on the speed bag or is there an unwritten rule you have to really have a huge range of motion with your fist or you are cheating yourself?

Every youtube tutorial I watch doesn't discuss this at all. They are basically people showing off. Thanks in advance.