How to Do a Plank Crunch, a Majorly Effective Core Exercise

Plank Crunch

Row House

In most core workouts, you're likely to encounter at least a few crunches and planks because they're both effective exercises in working the abs in different ways. Some people fall on both sides of the crunches vs. planks preference, but there's another exercise that combines the benefits of both of those separate movements into one: the plank crunch. Plank crunches work your entire core in a short amount of time so you can get the most out of even short ab workouts. We asked a couple of experts about how to do a proper plank crunch, its benefits, and how to level up and down if you want to try something new.

Meet the Expert

  • Michelle Parolini, AFAA, is a master coach for Row House.
  • Bethany Stillwaggon, ACSM, CPT, is a master coach for Row House.

What Is a Plank Crunch?

A plank crunch is what it sounds like: an exercise that combines two moves by crunching your abs while in a plank position. You drive one knee at a time to the chest or same elbow and then alternate.

What Are the Benefits of Doing a Plank Crunch?

When you do a regular crunch on your back, you’re mostly only working on the front of your core, says Michelle Parolini, AFAA, master coach for Row House. But with a plank crunch, “you are strengthening all of the muscles around the front, sides, and back of your core due to the plank, and then giving your abdominals a little extra work with the crunch,” she says.

Bethany Stillwaggon, ACSM CPT and master coach for Row House, explains further. “Most people forget your core involves your entire midsection: abs and back.” According to Stillwaggon, a plank crunch targets your entire core: Your posterior chain (the muscles on the backside of your body, from your lower back to your heels) actively works to hold your body in the plank position, and the abs on the anterior side of the body are used during the crunch portion.

“A plank itself targets a large portion of musculature in an isometric (stationary) way...your glutes, quads, deltoids, triceps, pectorals, latissimus dorsi (aka your lats), and abs. This alone is a great way to develop a more dense muscle and a more connected muscular system within the body since so many muscles are being used at once. By adding a knee drive to this, we’ve taken an isometric movement and added a moving component, which always will result in more need for stability...cue more muscles,” adds Stillwaggon. While you try to keep your body stable, the side driving your knee to your chest uses your hip flexors, obliques, and rectus abdominis muscles. 

Who Should and Shouldn’t Do a Plank Crunch?

Both Parolini and Stillwaggon agree that a plank crunch is low-impact and safe for most people, as well as a good option for anyone uncomfortable with crunches or lying on the ground. However, says Parolini, expecting mothers or anyone with shoulder or back issues may want to avoid them. And always consult a doctor if you have any concerns about trying a new exercise. 

How to Do a Proper Plank Crunch

  • Get into a plank position with your hands directly under your shoulders and body in a long, straight line. 
  • Based on your current fitness level of core stability, decide how far apart you want your feet to be (the wider your feet, the more stable you will be when lifting one leg off the ground).
  • Brace your core, drawing in your belly button, and push your palms into the ground, like you are trying to push the floor away from you.
  •  Bend one knee and drive that knee towards your chest.
  •  Return to a plank position.
  • Repeat with the other knee/leg.

The speed at which you drive your knees up is based on your preference. “The quicker you are, the greater the heart rate will be. The slower you are, the more challenging it becomes to your body’s stability and connectivity in your muscles. Both have benefits, so choose the speed that you feel best with or give both a try,” says Stillwaggon.

Regardless of your speed, however, Parolini advises trying not to let your lower back cave in while in the plank position or, conversely, let the hips pop up when performing the crunch.

What Are Some Plank Crunch Modifications You Can Do?

If you want to level down:

  • Parolini says to hold a plank to engage your core if you're not ready to add the crunch.
  • If you want to do the crunch, you can also modify your plank position to make it less challenging. For example, Stillwaggon suggests trying it on your knees or with your hands on the wall or a bench.

If you want to level up:

  • Engage your obliques by turning your plank into a side plank, either on your hand or elbow. From a side plank position, drive the knee that’s on top toward your elbow. (see image above)
  • Come down onto your elbows in a regular plank and crunch your knee out to the side. “That modification will engage more of your obliques,” says Parolini. 
  • Try a decline plank (putting your feet on a bench or a block). Says Stillwaggon, “This will not only put more weight on your hands, allowing your legs to move with more ease, but your upper body will now get the entire deltoid involved by having most of your body weight in your arms and shoulders.”
  • Elevate your feet up even higher. Put your feet up on a wall for an almost-handstand crunch. This will give more focus on the posterior chain connection as you drive your knee up to the chest and safely bring it back to the starting plank position, says Stillwaggon.
  • Add a twist. Instead of driving your knee up to your chest, drive it to your opposite arm’s elbow, across your body. Stillwaggon says, “Notice how your body is using your hip flexors, rectus abdominis muscles, and now your obliques and transverse abdominus to break into the transverse plane of motion.”

How Often Should You Do Plank Crunches?

Depending on how you feel and your goals, Parolini says you would probably be safe to do plank crunches in some capacity every day or a few times a week.

If you are just starting, Stillwaggon recommends starting by practicing over a short amount of time first. She recommends trying “intervals of 20-30 seconds and then see how you feel during and about a day after doing this new movement. If your body enjoyed the exercise, stretch and start to increase time and/or repetitions to see progression in the plank crunch.”

Because it involves compound movement, a plank crunch can be an efficient way to work out many muscles quickly. “Use this if you don’t have a lot of time or use it as you start to warm up for your rowing, biking, or running workout that all involve a stretch of the hips and firing of the abdominals.”

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