I watched this video the other day and thought it was pretty interesting. It talks about how crunches might be an exercise you should avoid doing too often because even though they will give you core strength it can harm other parts of your body. The hip flexors can be tightened along with a few other things, and most people already have tight hips from sitting all the time.
What do you guys think? Are they worth doing at least every once in a while maybe?