IF YOU’RE A serious runner, you’re probably not doing core workouts to better prepare your body to shoulder heavy weights or hone six-pack abs as your ultimate goal. Your aim is more likely to build up the rest of your body to support your high-mileage habit.

But you’re not going to be able to do that with some half-hearted situps and planks after you come in from your long run; you’ll need some more involved ab training to build the type of core you want. Men’s Health and Runner’s World have teamed up to give you the ultimate workout program, 20-Minute Functional Core (available through Men’s Health MVP Premium), which provides you with ab-training knowledge that borrows some weight room techniques so your cross-training can be as effective as possible.

Men’s Health fitness director Ebenezer Samuel, C.S.C.S. and Runner’s World coach Jess Movold lead you through the workouts—and they have a super effective movement you can use immediately to work your abs, lower back muscles, and obliques: the hollow hold.

The key to the hollow hold is bracing, a function of your core that helps to support the spine. “It’s going to make us that much better at all our lifts—and it’s going to make us that sturdier and that much more resilient when we’re running, too,” says Samuel.

How to Do the Hollow Hold

• Lie on the ground (preferably on a yoga mat). Get into an “egg” shape—raise your feet off the floor and hug your knees to your chest, lifting your shoulders off the floor.
• Drive your lower back into the floor. This is key for the duration of the movement.
• Extend your legs out as far as you can, straightening the knees and keeping your feet raised a few inches off the floor. Extend your arms out behind your head, keeping your shoulders raised off the floor.
• Squeeze your abs and glutes to create full body tension. Hold this position, keeping your lower back planted on the floor.

You can work up to longer static holds in this position, giving your core a tough isometric challenge. Once you can hold for a minute with solid form, give these variations a try.

3 Hollow Hold Variations for Runners

Perform each exercise for 40 seconds, then rest for 20 seconds. Repeat for two to three total rounds.

Tipping Hollow Rock

This will train anti-rotation, another key function of the core.

• Start in a strong hollow hold position.
• Without losing tension or lifting your arms or legs, shift your weight to your right glute and shoulder blade.
• Hold for two seconds and balance.
• After the hold, shift to the left side. Repeat, alternating sides for the duration of the set.

Hollow Rock

• Start in a strong hollow hold position.
• Lift your legs up to create some momentum, then begin rocking back and forth.
• As you rock, keep your lower back on the ground. Maintain tension in your abs and glutes.

Anti-Rotation Hollow Rock

As the name implies, this variation also hones anti-rotation. You’ll fight against gravity to keep your position from shifting.

• Start in a strong hollow hold position.
• Rotate one arm out to the side. One arm is straight above your head, the other is out to the side, forming an “L”.
• Begin rocking like the above exercise. After the work period, perform the next set with your arm positions swapped.

Want more helpful ab training moves from Samuel and Movold? Check out the entire 20-Minute Functional Core program, available as part of Men’s Health MVP Premium.