I recently purchased a resistance band a couple months back because I left my wieghts at my uncles and didnt have the time to go get them and lug them back,thank god it happened cause otherwise I might not have gotten a resistance band. I find that they give a very good work out, and using them for training punches is very good, better then punching with weights I think. Because with the weights you also have to fight gravity, keeping your arm up, therefore engaging muscles you normaly wouldnt use in a punch. As part of the physical fitness test for Shuri Ryu you have to be able to do 75 punches with 15lbs, which I can do about 100 now. I started throwing punches with the resistance band and found that it gives a MUCH better work out, the first time I tried it I was sore for a day and I didnt even throw 100 punches. It engages the muscles used much more effeciently then weights, i would HIGHLY recomend adding a resistance band to your training. Ive also noticed my punch has gotten alot better to in just about a month.
Let me know your opinion on resistance bands.