Core
Toes to bar are an advanced hanging leg-raise variant where the goal is for the feet to touch the bar each rep. They require hip-flexor strength, real abdominal strength, and posterior-chain mobility.
Hang from the bar with a firm grip. Brace the core in hollow body. Raise the straight legs in an arc until the feet touch the bar. Lower controlling the eccentric while staying in hollow body. Descent control matters as much as the raise.
No prior swing or kip. Movement starts from a still hang and the concentric is fully muscular. Much harder but far more effective for real core strength.
3 × 8-12 strict toes to bar is a solid intermediate-advanced milestone.