The Sit-Up has been around for decades and it's one of the first exercises taught by gym teachers and fitness trainers. You probably learned to do it in gym class, but it's highly unlikely that you learned the proper form. So, let's take a look at how you can do the "perfect" sit-up.
Lie on your back, relax your head and neck muscles.
Place your fingertips on your ears, and open your elbows out wide to the side.
Bend your knees and place your feet flat on the floor. Make sure they are spread to shoulder width.
Relax your back and try to avoid arching it. If you feel tension in the lower part of your back, you're doing it wrong.
Keep your chin away from your chest, as it stops you from breathing properly.
Using just the muscles of your stomach, bring your body off the ground to a 30-degree angle.
Breathe out as you sit up.
Push your feet into the floor, but keep them flat on the ground.
Keep your head and neck relaxed, and tilt your chin up to the sky if it helps you keep it off your chest.
Do not use your hands for leverage. Avoid pulling on your neck as you come up, as that could lead to a strain or crick in your neck. Your hands are simply there to make the exercise a bit more difficult.
Avoid sudden movements as you go up. Don't jerk upwards, but crunch slowly to avoid injuring your lower back and straining your core.
Hold at the top of your upward motion for a one count.
Use your stomach muscles to slowly bring your upper body back down to the floor.
Don't engage your back if your stomach muscles are tired. Your lower back should be relaxed AT ALL TIMES.
Inhale as you come down. Filling your lungs will oxygenate your blood, reducing the lactic acid burn that will cause your abs to cramp.
Don't go down too slowly, but don't drop back down either. Lower your upper body to the mat with the same speed as you went up.
Avoid moving your head as you go back down. The tendency will be for your head to drop to the floor, but keep your neck and head relaxed throughout both up and down motions.
Stop your neck from touching the mat. Only your shoulders should touch the mat as you lower yourself.
Keep your feet flat on the floor and avoid the temptation to use your legs to gain more momentum.
Don't do more than 30 reps without a rest. You'll lose technique as you struggle to reach your goal.
Don't go fast! Keep it slow and steady, as that will help you maintain proper form.
NEVER jerk. Slow, smooth motions are the key.
Don't pull on your neck. Pulling can strain your neck.
If you feel any muscles besides your abs working, you're doing it wrong. ONLY the abs should be engaged.