Planks vs. Crunches: Which Ab Exercise Is Better for a Stronger Core?

Planks work your entire core while keeping your lower back healthy.
Image Credit: SDI Productions/E+/GettyImages

Achieving washboard abs is a complicated proposition, and no one exercise alone is going to get you there. But when it comes to doing planks versus crunches, which abs exercise is your best investment?

While crunches might be a staple in your ab workouts, it's possible they're doing more harm than good.

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Read on to learn why crunches can be ineffective — and potentially painful — and why you should be doing planks instead.

The Problem With Too Many Crunches

Crunches can make your abs burn, but they aren't always as effective as that singe might lead you to believe.

Crunches only work a small portion the many muscles that compose your core. They isolate your rectus abdominis, or six-pack muscle, to help develop visible results, but don't highly engage the deep-lying core muscles that are critical to strength and function.

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That isolation is what makes your abs fatigue. Muscular fatigue isn't necessarily a bad thing, but it can force your body to rely on other muscles to power the exercise, says Samuel Chan, PT, DPT, physical therapist at Bespoke Treatments in New York City.

That's why, when people try to build their abs with only crunches, they often end up training their hip flexors instead — and get no closer to their core goals.

Even more problematic, crunches, when performed improperly, can increase the risk of injury.

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According to Harvard Health Publishing, pushing your curved spine against the floor during crunches can stress the spine to cause lower-back pain.. They can also compress the front portion of the spine, which may possibly lead to increased pressure on the discs between your vertebrae, says Samuel Chan, PT, DPT, physical therapist at Bespoke Treatments in New York City.

Neck pain is another common crunch problem, Chan says. As you start to tire out after a few sets, you may begin to crank your head and neck up to complete the crunch. As with hip-flexor compensations, tugging on your neck means you're not using your abs to their full potential. It can also strain your neck muscles.

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Why You Should Do More Planks

Swapping out some of your crunches for planks makes for a safer, more effective ab workout, Chan says. Unlike sit-ups and crunches, planks target muscles across the entire core, while keeping the spine in a safer position, he says. Planks also engage your shoulders, lats (upper back), quads and glutes to maintain a straight line from head to hips to heels.

But as with crunches, you'll need to maintain proper form in order to get the most out of your planks and reduce stress on your lower back. Focus on maintaining total-body tension (squeeze everything!) to keep your hips in line with the rest of your body.

Here's how to do a plank correctly:

Low Plank

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Skill Level All Levels
Activity Body-Weight Workout
Region Core
  1. Start on your hands and knees and place your forearms on the ground, elbows directly beneath your shoulders.
  2. Extend your legs straight behind you with your toes tucked.
  3. With your core braced and quads and glutes tight, press into your toes and forearms to lift your body off the ground.
  4. Keep your back flat and your body in a straight line from head to hips to heels.

Tip

"[Raising the hips] is a common compensation of the hip flexors due to weak lower abdominals," Chan says. "You can avoid this by engaging your glutes along with the abs. Think of flattening out the arch of your low back and tucking your tailbone."

Try These 4 Plank Variations for a Stronger Core

Although crunches are a one-trick pony, there are plank variations for every fitness level. You can make your plank easier by dropping to your knees, adding an incline or holding the pose for shorter periods of time. Make it more challenging but adding a leg raise or turning it into a mountain climber.

Here are a few plank exercises that will help you build a strong core.

1. Single-Leg Plank

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Skill Level Intermediate
Activity Body-Weight Workout
Region Core
  1. Start on your hands and knees and place your forearms on the ground, elbows directly beneath your shoulders.
  2. Extend your legs straight behind you, toes tucked.
  3. With your core braced and your glutes and quads tight, press into your toes and forearms to lift your body off the ground.
  4. Keep your back flat and your body in a straight line from head to hips to heels.
  5. With your body stable, raise your right leg a few inches off the ground. Pause here.
  6. Bring your leg back down and switch sides.

2. Forearm Side Plank

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Skill Level Intermediate
Activity Body-Weight Workout
Region Core
  1. Lie on your side and prop yourself up on your bottom forearm. Your elbow should be directly under your shoulder to avoid putting too much pressure on the joint. Your legs should be extended straight out with your feet stacked on top of each other.
  2. Keeping your hips square and forward, lift them off the ground. You should be able to draw a straight line from your heels to hips to head.
  3. Hold this position for as long as you can with good form, then switch sides.

3. Side Plank With Knee Tuck

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Skill Level Intermediate
Activity Body-Weight Workout
Region Core
  1. Start in a side plank balancing either on your hand or your forearm. Your elbow should be stacked directly under your shoulder. Keep your body in one straight line from your feet to your shoulder as you raise your top arm up toward the ceiling.
  2. Use your oblique muscles to bend your top knee and top arm until your knee meets your elbow.
  3. Lower your leg down and straighten your arm.
  4. Complete all your reps on one side before switching to the opposite side.

4. Side Plank With Reach Under

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Skill Level Intermediate
Activity Body-Weight Workout
Region Core
  1. Start in a side plank balancing either on your hand or your forearm. Your elbow should be stacked directly under your shoulder. Keep your body in one straight line from your feet to your shoulders as you raise your top arm up toward the ceiling.
  2. Use your oblique muscles to reach your top arm under your midsection.
  3. Pause here for a moment.
  4. Return to the starting position by extending your top arm back to the ceiling.
  5. After you've completed all your reps, repeat on the opposite side.

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