The bar muscle-up is a great display of relative upper body strength. This complex movement combines two movement patterns into one exercise:
Take a look at these two versions:
This version relies more on strength than generating power from the hips. The hips are used to initiate the movement but the lats are used to pull yourself up and over the bar.
This version creates greater momentum from the hips. The thought here is to bring your hips to the bar, though you may notice that my hips don't go all the way to the bar here. This is because there's another bar below the top bar where I'm doing the muscle-up.
You should have a strong upper body and solid core strength before attempting the muscle-up. Trying to kip your body up really hard to get your first muscle-up will lead to a shoulder injury if you haven't developed the strength or technique to do it.
Be sure you're able to do these three things before attempting a bar muscle-up:
If these are things you can do, then you're ready to learn to do a muscle-up.
If you just jump into this exercise, odds are you're going to try to snake your elbows over the bar and get stuck halfway. To avoid injury, master these moves first.
You need to be able to move your hips explosively and engage your lats. Think arch versus hollow. Here's what that should look like:
The arch is when you bring your chest forward and the hollow is when you retract your shoulder blades and engage your core.
Hips initiate the movement and give you power. Lats are responsible for adduction. Think of pulling your elbows into your sides and sliding your shoulder blades to your back pockets.
An explosive pull-up where you attempt to get your chest up to the bar is a great way to start.
Wrap your thumb around the bar. This will make for a much safer transition when you first start to learn the muscle-up. There are those who can and do use a false grip (thumb on top of the bar), but unless you're an experienced gymnast I wouldn't recommend it.
When you do the transition, think about performing the opposite motion of revving a motorcycle. Instead of throttling back, you throttle your knuckles forward and over the bar, stacking your wrists on top. Having your wrists stacked on top of the bar will give you more bone support as you prepare to go into the dip.
When you first start practicing your transition, try starting with a large elastic band.
This will allow you to practice rolling your wrists on top of the bar without wasting a bunch of energy on your pull-up.
If you pulled yourself up high enough and you stacked your wrists on top of the bar properly, the dip should be the easiest part. When you go into the dip, your shoulders should be stacked over your wrists. Keep your shoulders tight as you extend your elbows. Don't lose core tightness during the dip. Practice doing straight bar dips before attempting the muscle-up.
When first learning muscle-ups, don't try to do more than three at once. Keeping your reps low will ensure that you're using good form and are moving explosively during each rep. Adding more reps should only be done after you can do three muscle-ups with excellent technique.