Calling all fitness junkies: here's the ultimate way to test your mental toughness—and your physical toughness, of course. You may be in great shape, but that doesn't mean you've reached your peak—and the results of these tests won't give you any place to hide.So give these six demanding challenges a go and see how you stack up. Some test your cardio while others will challenge your brute strength.And no matter how you do, once you get through each of the challenges, take a look at your weaknesses—whether it's endurance, power, or getting in your own head—and start to incorporate those areas into your routine and keep making progress. [RELATED1]