We all know how difficult pull ups can be for beginners. Getting even one pull up can be an accomplishment. Additional reps come with the additional strength you gain from your workouts. A great way to start training your muscles to do natural, unassisted pull ups is to start off doing jumping pull ups. With a jumping pull up, you use the upward momentum of your jump to assist your muscles in getting your chin above the bar. The key is to let yourself down slowly, and make your muscles work on the way down.
Watch the following video, as Danielle demonstrates doing jumping pull ups, and turning them into negatives.