In the video above, Men's Health Fitness Director BJ Gaddour combines an isometric shoulder raise with a high-knee run. He calls the new exercise "iso-shoulder runners."

It's a supersmart movement that we hope goes mainstream. That's because it's ultra-effective at strengthening your shoulders and core, and improving your conditioning all at once.

Related: The 70 Best Bodyweight Exercises to Seek and Destroy Fat

(Get fitter faster with an activity or health tracker. Head to Best Buy to find the one that fits your needs and goals.)

The iso-hold allows you to keep tension on your shoulder muscles longer, which helps spur growth. And since your lower body is moving up and down, your stabilizing muscles have to work harder to keep your arms steady. The faster you go, the harder this will be.

There are several ways to use iso-shoulder runners. You can plug it into a total-body circuit. Or you can do for 20 seconds and then rest 10 seconds. Repeat that 5 to 10 times in a row.

Related: The 21-Day MetaShred Will Strip Away Fat and Reveal Lean, Hard Muscle

Use both weights at once, or go with a single weight in one hand to challenge your opposite obliques.

You can also mix up where you hold the weights -- in front of your body, out to your sides, or overhead -- or stick to one position the entire time.

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

Story continues below