What happens when pull up?

A pull-up looks like an arm exercise. It's a back exercise that your arms happen to finish. The order is the whole thing. Before your elbows bend at all, your shoulder blades pull down and together. Middle traps and scapular retractors firing while your arms are still straight. Then your lats take over and do the actual lifting as your elbows drive toward your ribs. Your biceps only finish the top. Your grip and forearms are loaded the entire time. Get that order wrong and you're doing a different exercise. Bend the arms first and your biceps take work that belongs to your lats, your shoulders shrug toward your ears, and your back barely turns on. Same effort, almost none of the benefit. And if you can't do one yet, it usually isn't strength. The muscle is already there, but your nervous system just hasn't learned that firing order. Click the bio link and I'll send you a blueprint to get your first pull-up.