Hang from the wall bars and grip the rungs firmly with both hands. Your arms should be almost fully extended. Let your legs hang loosely downwards; keep your torso stable and your shoulders actively pulled down. Raise your straight legs forwards or upwards in a controlled manner. Perform the movement primarily by bending at the hips and whilst actively engaging your core. Then lower your legs slowly and in a controlled manner, without letting them swing back uncontrollably.
Attention:
Do not use momentum from your upper body; do not arch your back excessively as you lower yourself; do not pull your shoulders up towards your ears; do not simply let your legs drop; keep your core engaged throughout the entire movement.
Lighten:
Perform with bent knees (knee raise); lift your legs only partially, using a smaller range of motion.
Harden:
Use extra weight on your legs; lower the bar more slowly, hold briefly at the top of the movement.