Pulling from the elbow is the first step. Next time you’re hanging from the chin up bar, before doing your set, try this...

Grab the bar with an underhand grip at about shoulder width and hang with your arms straight.

Now pull your shoulder blades all the way back. Imagine trying to pinch a pen between them.

When you get the hang of this, you’ll pull your chest about three inches closer to the bar without bending your elbows.

This is your starting position. Practice just doing that a few times and get used to how it feels.

This technique should be used at the beginning of each rep before you start to bend your elbows. It'll make sure you’re using your back to do the work and not your arms.