Curl-ups

• Lie on the floor on your back with your knees bent at a 90-degree angle. Your feet should be flat on the floor, about 12 in. (32 cm) from your buttocks.
• Cross your arms over your chest.
• Slowly contract your abdominal muscles and raise your shoulder blades off the floor.
• Keep your head in line with your body; don't press your chin to your chest.
• Hold this position for 1 or 2 seconds, then slowly lower yourself back down to the floor. Repeat 3 to 10 times.

From Healthwise