According to research from Dr. Stuart McGill (backfitpro.com) and his book "Ultimate Back Fitness and Performance" – crunches produce very high levels of intra-disc pressure and do not train the abdominals to produce spinal stability. Your abdominals are meant to be stabilizers not movers. The rectus abdominus (the 6 pack muscle) is not really a flexor anyway. It's actually there to provide increased "hoop tension". If possible read anything that's related to 'resistance to twisting motions'.
In simple terms, our abs are not meant to provide flexion but to stabilize. With this in mind, how many real life activities can you think of which requires you to do a crunch? Doing lots of crunches can lead to overuse injuries of the spine.
The better alternate
Planks are far better exercise for abs when compared to crunches.
To perform a plank:
- Get down into a prone positon on your elbows and toes and make your whole body tight while squeezing your abs and glutes. The goal is to make a straight line from head to toe while holding this position for a predetermined amount of time. Do note that you need to do side plank on both the right and left sides.
- Aim for holding each position for at least 30-45 seconds and work your way up to 1-2 minutes. Further progression can be made adding external load or lifting one limb in the air creating further imbalance.
- Holding for 1-2 mins would be very tough if you are trying for first time. This is one exercise that looks simple enough to perform but its a lot difficult then what it may seem.
Here are 2 videos on how to do a plank:
- If you want visible abs then get your body fat down, no matter how much ab work you do your abs would not be visible until the fat covering it is gone
- Abs are "made in kitchen", so keep what you put in your mouth at check
- You can not go wrong with heavy squats, deadlifts, or overhead lifting
- Overhead squat is the best strength training exercise that you can do for your core