Another question I received today:
Which exercise is better, sit-ups or crunches?
Answer: neither. Asking which is better, sit-ups or crunches, is like asking who’s funnier, Robin Williams or Ellen Degeneres. They’re both awful.
Stop doing crunches, and don’t bother doing sit-ups either. All you need to safely and effectively exercise your core is traditional compound resistance training exercises combined with static and dynamic plank exercises.