When it comes to strength training, I tend to make my moves relatively slow, controlled, and deliberate. But according to a post on Women's Health, there can be benefits to adding a little speed when you're doing crunches.

A recent study on the subject was published in The Journal of Strength and Conditioning Research. The lead researcher of the study says that fast crunches -- where the up and down movement is completed in one second -- make your external obliques do some of the work.

If you want to try some fast crunches, think of it like interval training for your core. Do your regular ab workout -- at a regular speed -- and add a few fast crunches for good measure.