One of the more challenging dip variations, the straight bar dip, is also one of the most specific precursors to the muscle-up. Don't start working on them until you can do a set of at least ten consecutive dips on parallel bars.
Straight Bar Dip
The straight bar dip is performed with both hands on a single straight bar positioned in front of the body. Your grip should be within a few inches of the width of your hips, though you can experiment with wider or closer hand positions. Like a bench press, close grip tend to be more difficult.
When you dip on a straight bar, your body must move around the bar. As you lower yourself down, you'll need to lean over the bar and reach your legs out in front a bit to keep balance. This causes further abdominal activation while demanding more from the shoulders and traps.
Don't let your shoulders shrug as you lower yourself down, and pay attention that your arms don't flare out to the sides. Your elbows should point behind you at the bottom of the rep.
Just like parallel dips, make sure you get all the way down when you dip on a straight bar. You should aim to touch your chest to the bar and achieve the same 90-degree angle outside of your elbows at the bottom of each rep.