While it’s not necessarily wrong to leave your thumbs on top of the bar, it’s not the best either and here’s why. Wrapping the thumbs is safer, more efficient, and has more skill transfer to other moves.
The last thing you want during a set of pull ups is to fly off the bar. Leaving the thumb on top of the bar just isn’t as secure as wrapping your thumbs. It’s a lot harder to lose your grip when your fingers go all the way around. A tighter grip also allows us to have better control and activate more muscles in our arms, spreading the load and slowing the onset of that dreaded forearm burn. Lastly, the biggest reason to wrap is skill transfer. Barbell, dumbbell, rope climbs, you name it. We would never hold any of those implements without wrapping the thumb (please don’t try!).
If you’re used to putting all your fingers on top of the bar, this change won’t be easy and it’s going to feel unnatural in the beginning. Sounds a little like CrossFit, difficult and unnatural at first, but the more you do it, the better you’ll become. Now, let’s get to work!
Move well. Eat clean. Be happy!