One arm dead hangs are used in our Bouldering Strength and Power Program.
When completing one arm dead hangs make sure that you are using an open handed grip, your body remains calm, and you’re not kicking your legs. You also want to ensure that you focus on stabilizing your shoulder by keeping your shoulder blade back and down as much as possible.
If it is to difficult to perform bodyweight one arm dead hangs, you can remove weight with a pulley system, or by connecting a rope to the bottom of the hang board and removing weight with your free hand.
Warning:
Do not complete one arm dead hangs if you are currently suffering from a finger injury, you are bouldering less than V4, or are experiencing any pain in your fingers, shoulders, or elbows.
Great information! However, the warning is in my opinion a bit off. I would say that you should be climbing at around V8 or higher to do these hangs.
Interesting article on how to get the fingers strong!