Past a certain very basic level of competence, most people are unable to either begin or continue building maximal strength when training the muscle-up. Why? The problem is actually four-fold:
1) The athlete is physically weak through out the transition portion of the muscle-up. Other than gymnasts who are either preparing to or are actually training the iron cross and other more advanced ring strength elements, most people have never developed extreme strength in this range of motion (ROM).
2) The athlete is unfamiliar with the technical aspects of the transition and it usually takes some time to learn the correct coordination of moving from a pull-up to a dip.
3) The athlete learns to use momentum and begins to kip through the transition completely. This is acceptable for a raw beginner not yet capable of executing a strict muscle-up. However, continuing to use the kipping technique once the athlete is capable of 3-5 reps, is simply sidestepping the strength development that he was seeking in the first place. This gives an artificial sense of accomplishment, but little to no long-term strength gains.
4) The athlete fails to move on to harder muscle-up variations. This is key. Variations include, but are certainly not limited to: kipping narrow grip (inside shoulders), kipping medium grip (shoulder width), kipping wide grip (outside shoulders), kipping wide with no false grip and then proceeding through the order again but this time strictly with no kipping. Of course weights may be added to any of the above strict variations.
I have yet to see someone able to perform a kipping muscle-up with half their bodyweight hanging on them. That much weight precludes any possibility of kipping. The only way to manage a muscle-up of this magnitude is with pure raw strength built from years of dedicated and progressive effort.
And yes, my own elite athletes were capable of performing strict MU with nearly half their bodyweight added.
Strength development progress does not arise from beating one particular variation to death, but in understanding the basic movement, the subsequent progressions associated with it and then carefully proceeding through the kipping to strict variations. It should also be remembered that there are far harder exercises than a muscle-up. Once you are proficient and have progressed through the variations in question- move on.
Yours in Fitness,
Coach Sommer