Why do my knees come up to my chest when I do pull-ups?

[redmchalo]

I've finally gotten strong enough to do bodyweight pull ups, I can sets of 2 reps at 259 lbs bodyweight. I can get my neck to the bar for each rep and I can fully extend down all the way at the bottom of each rep. But what I have noticed, my knees come up towards my chest when I go to pull myself up. They hang steady at the bottom but they curl upwards when I pull myself up, it almost looks like I am doing a pull up/knee raise combo at the top of each rep. I've tried to keep my legs stationary but that makes the movement much difficult for me and I am unable to pull myself up even half way. It doesn't feel like I am kipping, but I am not sure if curling my knees at the top provides some "cheating"....not too sure. Is it fine if I continue to do pull-ups this way, I still feel them quite a bit in my lats. Or, should I keep my legs stationary?

[TolerantLactose]

I've tried to keep my legs stationary but that makes the movement much difficult for me and I am unable to pull myself up even half way. It doesn't feel like I am kipping

You're generating momentum with your legs, ie. you're kipping. It might be an unconventional kip but it's a kip.

[SuffolkPunch]

Yes, it makes it easier to do a pull up...

If you are training to get better at pullups or to grow muscle, it doesn't matter too much - but if you want to compare one performance to another, you have to do it with a consistent form otherwise you aren't comparing like with like.

[Heisman2]

When you raise your legs up at the start and then actually pull yourself up your legs do not have to go up with the rest of your body; they can actually move down while your upper body moves up. This, you are decreasing the total weight you have to move by doing this.

That is not good if you are in a strict pull-up competition. For training purposes though there is nothing wrong with it.

[Casca]

I don't know how tall you are, but 259lbs is a lot to be pulling up with. Kicking up hard enough where your knees gets anywhere near your chest......I think you are better off using bands to assist you or just doing leg assisted pull ups. Leg assisted is just keeping feet on ground or an elevated platform but using as little support from your legs as possible to do the movement.

Kicking legs up is not quite kipping, but it's the same idea....just not as thought out. You're using momentum generated from muscles that has nothing to do with pulling to lighten yourself as you pull up. Doing it that way probably isn't going to be good for your joints, ligaments, shoulder health, I'm not an expert but I don't think it's a good idea to be doing that. You are better off doing controlled movements and using bands or leg assist to make yourself light enough to be able to do the movement.

[broganoff]

Not directly related, but a form cue I heard somewhere was "pull up like you are going to put your hands in your pockets" if that makes sense. Definitely helps with lat engagement.

[air2fakie]

Not directly related, but a form cue I heard somewhere was "pull up like you are going to put your hands in your pockets" if that makes sense. Definitely helps with lat engagement.

Probably was "elbows in your back pockets".