You can’t deny the importance of a good core workout. But having to memorize what feels like 100 different exercises that hit all the important muscles can be tough. That’s why Amber Rees, Barry’s instructor and Nutrition - Weight Loss cofounder, created this four-week progression that uses the same moves each week so you don’t have to commit countless circuits to memory or spend a ton of time trying to find new workouts.

Rees’s workout only takes 20 minutes to conditional, and each week you do it, you’ll increase the amount of reps or add weight to make it more challenging.

“Do this set of exercises once a week for a month to hit every major core muscle leg strength, reduce injury, and enhance posture. Not only that, it will help you build your overall power, increase your turnover, and result in more consistent training,” Rees says.

You cant deny the importance of a good: The workout is a four-week challenge. Perform the workout once a week in addition to your regular running routine and other cross-training (if you do any type of cross training). Follow the allotted amount of sets and reps below.

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High Plank to Alternating Step-Up

Begin in a high plank position with wrists directly below shoulders, and feet shoulder-width apart. In one motion, bring right foot forward to come into a low lunge position, then drive left foot forward as you stand up on right leg into a knee drive with left knee bent to 90 degrees. Bring left leg back down to the ground, followed by your right leg, to come back into high plank position. Repeat, this time starting with your left leg.


Squat With Alternating Rotation

Start by standing with feet shoulder-width apart. Send hips back and bend knees to perform one squat, making sure chest stays lifted, you’re shifting your weight back into your heels, and pushing your hips back. Return back to standing position, then rotate your torso to the right while bringing your right knee across your body in a tucked position. Return to standing, then rotate your torso to the left while bringing your left knee across your body in a tucked position. That’s one rep. Repeat.


Reverse Lunge With Rotation

Start by standing hip-width apart, hands behind your head. Lunge backward by stepping left foot back, engaging your core and bending both knees to 90 degrees. Rotate torso to the right and then back to center. Return to starting position by stepping left foot foot back up to standing position. Repeat, this time stepping right foot back and rotating torso to the left. Continue alternating.


Plank With Toe Tap

Start in a high plank position with wrists under shoulders, core and glutes engaged so body forms a straight line from head to heels. Lift hips up and back to reach right hand to left foot—your body will form an inverted V-position. Return to high plank position. Repeat, reaching left hand to right foot. Continue alternating.


Forearm Side Plank With Hip Dip

Start on your side with your left forearm on the ground, forming a straight line from your head to your feet, feet stacked on top of each other (your elbow or hand should be directly under your shoulder). Lift hips as high as you can, then dip your hips and tap them on the ground. Return to starting position, then repeat for the total number of reps. Flip over and repeat on the right side.


Crunch

Lie faceup on the ground with your legs perpendicular to the floor. Bend your knees 90 degrees and flex your feet. Lace your hands behind your head, squeezing your shoulder blades together and pulling your elbows back without arching your low back. Brace your core and curl up until your upper back is lifted off the mat. Lower back down to starting position in a controlled manner. Repeat.


Sit-Up

Lie faceup on the ground with your knees bent, feet flat on the floor, and heels about 12 inches away from your tailbone. Your arms should reach straight above your head—your biceps by your ears. Brace your core and sit up until your back is straight and lifted entirely off the ground. Lower back down to starting position in a controlled manner. Repeat.


Rock Back With Russian Twist

Start lying faceup with knees bent at 90-degree angles, feet in the air. Draw chest up toward knees to come into a V-position, using your core to balance on your tailbone. From your torso, twist right so hands comes to right hip then twist left so hands comes to left hip. Return to center and slowly roll back along your spine. Use the momentum to rock back up to V-position and repeat.


Jackknife

Lie faceup on a mat with legs straight, arms extended straight overhead. Lift legs straight up so your body forms an L-shape and lift shoulders and upper back off the mat to reach hands toward feet. Lower arms and legs down so feet are a few inches off the ground, and then repeat, drawing hands and feet toward the ceiling to meet again.


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From: Bicycling US
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Danielle Zickl
Senior Editor
Danielle Zickl for Runner's World and Bicycling.