How to do it

Lie on your back on a mat or the floor, with your knees bent and feet flat on the ground. You may hook your feet under a stable object or have a partner hold them for added stability.
Hold a dumbbell, weight plate, or medicine ball against your chest with both hands.
Engage your core, exhaling as you begin to lift your upper body off the floor, curling your torso towards your knees. Keep your neck in line with your spine, avoiding yanking it forward.
Continue to lift until your chest is close to your knees or you reach a comfortable upright position where your abdominals are fully contracted.
Inhale as you slowly and in a controlled manner lower your torso back to the starting position. Avoid letting gravity just drop you down.
Repeat for the desired number of repetitions, maintaining control throughout the movement.