Crunches are the easiest most well known exercise to strengthen your abdominal muscles.
They're a lot like sit-ups, but instead of lifting your entire back off the floor, you only lift your upper back.
This isolates the rectus abdominus muscle (the six pack) without engaging muscles in your hips. This exercise also does not engage the deeper core muscles.

Exercise Video

How to do

  1. Lie on your back on the floor. Bend your knees, keep the feet on the floor.
  2. Cross your arms in front of your chest, or place them behind you neck.
  3. Lift your shoulders towards the ceiling using your abdominal muscles and pause at the peak. do not lift your entire back off the floor.
  4. Ease back down slowly as you inhale.

  5. Its is better to put your hands on your chest, when putting hands behind the neck people tend to pull themselves up with their hand which causes neck pains, and a less effective workout.

    Try to keep looking up at the ceiling. It can be tempting to move your head forward because it makes you feel like you're lifting further, but you're not. It's a bad habit that increases your chance of getting injured. One good way to prevent this is to always try to keep looking up at the ceiling.

    Keep a slow pace on the way down Don't just fall back, the lowering down works your ab muscles as well.

    Don't go too high The crunches are made to isolate the rectus abdominus muscle (the six pack), going to high will engage your hip flexors making the exercise less effective. Make sure your lower back stays on the floor.

Risky for the lower back if you go too high

Crunches are pretty good strengthening your abs, but you might throw your back out in the process.
Crunches, or worse, sit ups, involve flexing your spine repeatedly, which get worse if you add load to it, like a weight plate.
Too much flexion is the exact mechanism that causes injuries like a herniated disc.
To stay on the safer side, try to hold your spine flat on the floor as you bend.

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