The emphasis here is on core strength. Choose a hold that you’re fairly comfortably on. You can dead-hang or bent-arm hang. Pull your legs up from the hips, keeping your knee straight. Hold a static contraction with your legs at 90° to your torso or do slow repetitions raising your legs as far as you can. If straight leg raises are too difficult, bend your knees at a 90° angle.
(All information has been taken from the Metolius brochure).