Lie on your back with legs extended, toes flexed, and arms at your sides, palms down. Press your lower back firmly into the floor, maintaining this position throughout. Engage your core and lift legs straight, pulling your belly button towards your spine. Raise legs to 90 degrees (or as far as form allows), pausing briefly at the top. Slowly lower legs over 2-3 seconds, stopping just before the floor. Keep legs together and straight (slight knee bend acceptable). Hands on the floor provide stability; place behind head only if lower back remains flat.
Maintain a flat lower back against the floor. Control your leg movement, avoiding momentum. Lower your legs slowly and deliberately. Exhale during the leg lift, inhale during the descent. Extend your legs as much as your core strength allows.