BTW...I found a trick out a while ago to strengthen my upper back tremendously that allowed me to perform the one arms shortly after. Get two towels and put one right next to your inner part of your hand on both sides. Do as many regular pull ups you can do normally.. right before you feel like you can't do anymore grab the towels and hang literally until you loose all strength and grip. I rested 5 mins between sets. After a few months of doing so every 3 days, you should be good
