Of all the articles I have written for Active.com over the last few years, guess which one continues to get the most hits? The one I wrote outlining the 8 best core-strengthening exercises for endurance athletes!

It's not surprising since buzz words "core" and "abs" seem to be thrown around quite often these days. You can't pick up a fitness or beauty magazine without seeing a headline like "How To Get The Best Abs in Hollywood." But just because a fitness model or celebrity has washboard abs, doesn't mean that she has a strong core or that she would be able to handle a rigorous endurance event. For that, you'll need to include some core work into your fitness routine.

So, How Much Core Work Should I Be Doing?

2-3 days a week (at most) for no more than 15 minutes each. I want to clarify that I am only referring to isolated ab exercises. I recommend doing ab exercises that can easily be measured so you can see your progression; weighted plank (heavier weight), russian twist (heavier ball) and renegade rows (heavier dumbbells).

If you suffer from tight hip flexors, you should stay away from exercises that may make the problem worse such as crunches, sit-ups and hanging knee raises.

While your strength training program should definitely include core work, you should rarely make it the focus.

image by Richard Yuan, Flickr

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