Re: Novice Advice
You're a big guy so I'd recommend at least a 100 lb. bag. They can be as light as 40 or so lbs. but in my opinion the lower weight bags are a waste of time and money.
For years I used just my hand wraps and a set of lightly padded bag gloves to hit the heavy bag with no problems. The last gym I went to had a few dozen pairs of 12 oz. gloves with velcro closures to use on the heavy bags. Doing this will help with endurance because of the extra weight.
As for any wrist problems, use your wraps to reinforce the area of the wrist and more importantly, learn proper punching technique. Trust me, if you hit that bag wrong and your wrist bends violently, it is quite painful and takes a while to heal. I did this early on a couple times when learning to throw a proper left hook.
I've given this advice before about how to help lower the risk of wrist injury as it has worked for me. Make a fist and hold out your arm parallel to the floor in front of your face. I like the top of my hand, wrist and forearm to all be on or near the same plane when striking the bag. If the top of your hand is elevated up or tilted down a good bit, that is just inviting it to be bent even more and causing an injury.