This piece first appeared on Women’s Running.

Your core is a powerhouse. Think of your middle—abs, back and hips—as the center of your movement. To run efficiently (i.e., faster with less effort), your center must be stabilized while your arms and legs propel you forward.

A tough core is the key to a strong center. Weak core muscles create unnecessary work for other parts of your body—which is wasted energy that delays you from tapping into your true runner potential.

Translation? A  muscular midsection is crucial to becoming your most efficient  runner self. Training your core will help you nail a new PR—and give you some enviable abs.

If you’ve neglected your middle in the past, make it your first priority before you head out for a run. These body-weight-only exercises make it easy—with static, rotary and dynamic stabilization. This session takes only a few minutes—so you’re out of excuses!

Two to three times a week, do one exercise from each category (static, rotary and dynamic) before heading out for a run.

What About Crunches and Sit-Ups?

Research done by Dr. Stuart McGill, a professor of spine biomechanics, shows that crunches may contribute to back injuries—and that stabilizing exercises (where your spine remains straight) are actually more effective at activating the abs. This is especially true for runners, who need to have the strength to stabilize their core while quickly moving their legs and arms to propel themselves forward.

The 3 Types of Core Exercises

STATIC: Hold Still. Starting with a static exercise teaches your body to stabilize. By bracing your core muscles without movement you build that strength. Choose one from this category before your run.

ROTARY: Add a Twist. When you run, you’re propelling yourself by  moving the opposite arm and leg to create  rotational force across your body. Rotary exercises help you make that movement more efficient. Choose one from this category before your run.

DYNAMIC: Go Full Body. By performing dynamic exercises, you will be able to swing your arms and legs without letting your body move too so that you have a stable center for your movement to come from. Choose one from this category before your run.

Here are examples of all three types:

Static: Plank
Static: Side Plank
Rotary: Russian Twist
Rotary: T-Stabilization
Dynamic: Bird Dog
Dynamic: Mountain Climber
Dynamic: Dead Bug