Lately, I hang around Rosstraining.com's forum. One thing that piqued my interest not too long ago was a guy who wondered if kipping on pull-ups or chin-ups is cheating. There was some interesting viewpoints on both sides. Ross brought up that since there isn't a pull-up competition, then how can kipping be cheating.
I half-agree with his statement. Okay, there is no international pull-up competition where they judge your rep count and form. I got that part and I see Ross' viewpoint. He uses pull-ups as a means to an end. He trains people to compete in sports so the results in the rounds is all he really cares about.
That doesn't mean that the concept of cheating in training just because you're not competing with anyone. There's a good chance that you're cheating yourself! If you're constantly using momentum to get yourself up the bar, then you're robbing your upper body of the usefulness of the exercise. I have to keep that in mind when I'm training. Sure, getting to 25 pull-ups entitles me to some serious bragging rights but what good does it do for my body at the end of the day?
Now, I'm not saying that I think that Kipping a pull-up is cheating all the time. If you've just gassed out at 7 and you couldn't do the 8th in proper form if you tried, then I'm hardly going to say that you cheated. When you do an exercise, you should be doing everything that you can to get the most out of it. If you can't, then what is the point? If you need to make a pull-up easier by kipping a bit, then do what you need to do. When you can do pull-ups easily, then look for ways to make it harder.
Do I kip on pull-ups? Sometimes I do when I get really tired and I just want to get one last rep. I do have an evil twist on the theme: rather than let my legs go back to a dead hang, I'll leave them sticking straight (like an L).