Ring muscle-up vs bar muscle-up: which should you learn first?
Skin the Cat: Benefits and How to Progress It
Skin the cat is one of the most underappreciated movements in calisthenics. It builds shoulder active range of motion in the deep extension that almost nothing else trains, making it prerequisite work for back lever and many ring movements.
The movement: hang from bar or rings, bring your legs up and over your head, continuing until your feet pass under the bar and your body is in an inverted hang. Then reverse back to the starting position. The full range requires significant shoulder flexibility — specifically, the ability to take your arms from overhead to behind your back while bearing weight.
If you can't complete the full range, work the partial range. Bring your legs to inverted and lower to whatever your range allows. Never force the end range. Daily practice over 4-8 weeks will expand the shoulder flexibility needed.
Once you have the skin the cat, the inverted hang (bottom position) is your entry point for back lever training. The shoulder conditioning you've built will make the back lever progression significantly safer.