Performing one arm pull-ups is a true test of raw strength, and only very few will progress to that level.
In essence, there is very little difference between a one arm pull-up (with your hand facing away from you) and a one arm chin-up (hand facing towards you): your body will tend to rotate under the bar as you pull, towards a position that offers maximum efficiency for you. I personally find that one arm chins, or parallel grip pull ups are generally slightly easier.
The exercise is highly dependent on a high power to weight ratio, and it will test your grip strength to its limits at first. The prime movers for the one arm pull up are the biceps and brachialis muscles, with a strong emphasis on the latissimus dorsi.
The following progression will take time, make no mistake about it ; you
should be aiming to complete 6 sets of 6 repetitions of the given
exercise within a workout, with at least 3 min rest between sets.
first set is a warm up set: go back two or three levels in the
progression and perform that variation for 6 reps (at first, this will mean going back to the pull-up progression).
each following set ‘to failure’ (e.g. 6,6,5,5,4).
each new workout, you should aim to improve on the number of reps you performed
previously by at least 1, e.g.: (6,6,5,5,4)
you manage 6 sets of 6 reps, you are ready to move on to the next variation in
If you find yourself not progressing any longer, take a few rest days, then
1. One hand pull-ups: grab the bar with one hand, and grab your wrist with the other hand. This will primarily test your grip strength, and the exercise will feel like a very hard step at first. If your grip strength is too weak, you might want to simply perform one arm hangs for a few sessions, building up to 10 seconds or so. In essence, you are still performing a two-arms pull up, though the grip on your wrist meants you only receive reduced assistance from your secondary arm and lats. Make sure to work one arm, then the other. Keep alternating arms until you can manage 6 sets of 6 reps for each arm.
2. One hand pull-ups on the way up, eccentric one arm pull-ups on the ways down: perform a one hand pull-up then when your chin clears the bar, ...
... let go of your wrist and lower yourself under control to the count of 3 seconds.
3. Half one arm pull-ups: raise yourself up to a mid position using a one hand pull-up (secondary hand pulling on the wrist), then let go and complete the pull-up using only one hand. You might want to practice this exercise with slightly different ranges also (for instance, from only a slight bend in your elbow, to a 3/4 one arm pull up).
4. One arm pull-ups: at first, you will likely hit a sticking point in the extended arm position. Make sure to use the stretch-shortening cycle to get past this initial hurdle (this post on how to do one pull up will help you undertstand how the stretch-shortening cycle works).
Even being able to perform 5 sets of 1 one arm pull-up will constitute a significant achievement in itself!