Stand up. Now touch your toes. Did you do it without rounding your low back?

If your answer is "hell no," then you have a mobility problem. And that could be the reason your deadlift is suffering and your back hurts after a workout.

Related: The Best Stretch For Every Body Part

But you won't loosen up your backside with a few seconds of stagnant stretching before your workout. You need to really dig into the restricted area in order to lengthen the muscles and break up scar tissue, says Men's Health Fitness Director B.J. Gaddour.

Related: Download New Men's Health Personal Fitness Trainer iPhone and iPad App -- for FREE!

His recommendation: Two to five minutes of the hamstring smash drill, shown in the video above.

The exercise name sounds ridiculous. (And you'll look ridiculous, too.) But it'll pay dividends in your mobility and strength.

Skeptical? Give it a shot and then touch your toes again. It's mobility magic.

More Men's Health:
-- 22 New Ways To Crush Your Core
-- 23 Best Biceps Exercises
-- This Might Be The Craziest Mobility Exercise Ever
-- The J.J. Watt Workout