Here are two bright minds talking about why the crunch is bad for your back.
First, Dr. Stuart McGill.
Thank you Avery Johnson for making this video with daddy.
I’m excited to share Core X with you. The changes from Core H are simple. Core X is half as long – 5 minutes rather than 10 minutes – and no crunches. I trust Dr. Hansen’s opinion on core strength; at the 3:02 mark of this video he talks about why he doesn’t like crunches. This routine and short and sweet, but still challenging. Enjoy!