How To Do A Crunch, Explained In Detail + 6 Crunch Variations To Try

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A crunch is an abdominal exercise that primarily works your upper “six-pack” ab muscles, the rectus abdominis, and your obliques if you switch it up and do specific crunch variations.

As a crunch only targets your abs, it is not a compound functional exercise like a plank but an isolation exercise focusing only on one specific muscle group.

This guide will look at the fundamentals of a crunch, how to do it properly, its benefits, and six different variations you can try out in your strength training sessions.

A crunch exercise.

How To Do A Basic Crunch 

  1. Lie on your back, feet flat on the floor at hip-width apart and knees bent.
  2. Place your hands behind your ears or across your chest.
  3. Engage your abs and lift your shoulder blades off the floor, really contracting your abs.
  4. Bring your shoulders back to the floor.
  5. Repeat for the desired number of reps. 

The crunch seems like an easy enough exercise, but in reality, if you don’t use the proper technique, a few things could go wrong, and you could even face the risk of injury by straining your neck or back. To avoid this altogether, let’s take a look at some tips to ensure you are performing this exercise correctly and safely. 

Tips To Perform A Crunch Correctly 

  • Keep your head and neck relaxed at all times to avoid any straining. 
  • Use your core to lift yourself off of the ground. Your hands are placed behind your ears but are not there to pull on your head or neck in any way. If you tend to do this, cross your arms across your chest instead until you have mastered the movement. 
  • As with most exercises, perform crunches in a slow, controlled manner. Engage your abs and exhale while you contract, then inhale as you lower yourself back down to the floor.

Now that we have the technique down let’s look at the sister exercise to the crunch, the sit-up. 

Sit-Ups Vs Crunches

A sit-up differs from a crunch mainly because the range of motion is more extended. In a crunch, your lower back should always be on the floor; however, with a sit-up, your entire torso comes off the ground as you must raise yourself up to an almost seated position.

Therefore, a sit-up works a wider variety of muscles, in addition to the rectus abdominis.

The muscle groups worked during a sit-up include the abs (rectus abdominis and transverse abdominis), obliques, hip flexors, and even your lower back. Since there is more movement, more muscle groups are recruited during the sit-up than when doing a crunch.

How To Do A Basic Sit-Up

Like the crunch, ensure you do not pull on your head or neck or use momentum to lift your body off the floor. You must engage your core to roll yourself up.

If you need a bit of extra help, approach the sit-up the same way in this video, arms extended next to your body. It makes the exercise more achievable if you don’t have quite enough core strength to get yourself up easily just yet.

  1. Lie on your back, feet flat on the floor at hip-width apart and knees bent.
  2. Place your hands behind your ears, across your chest, or by your sides.
  3. Engage your core, exhale, and lift your upper body off the floor, bringing it to your bent knees.
  4. Inhaling, lower yourself back down to the floor in a controlled manner.
  5. Repeat for the desired number of reps. 

Benefits Of Sit-Ups Vs Crunches

A person doing a sit-up in a gym.

Crunches strengthen your abdominal muscles and can improve muscular endurance, which helps to improve posture and perform daily activities where core muscles need to be recruited.  

Sit-ups recruit more muscle activation as you must pull yourself up to a seated position and work on your core stabilization. They can also help improve your posture.

Now that you have the basic instructions to perform a sit-up and crunch properly let’s check out some variations that you can add to your strength training to spice your workouts up a bit! 

6 Crunch Variations 

#1: Straight Leg Crunch

This first variation is similar to the basic version of this exercise, but instead of bending your knees with your feet flat on the floor, you extend them straight out in front of you. 

  1. Lie on your back, legs extended, and heels on the floor.
  2. Place your hands behind your ears or across your chest.
  3. Engage your abs, lift your shoulder blades off the floor, and contract your abdominal muscles. 
  4. Bring your shoulders and torso back to the floor.
  5. Repeat for the desired number of reps. 

You can also increase the difficulty by extending your legs straight up, perpendicular to the floor. This will engage your lower abs even more.

#2: Bicycle Crunch

After you’ve mastered the basic version of this exercise, why not take it up a level and increase the muscles activated with a bicycle crunch? 

Here, you will really feel your obliques as you rotate your torso from side to side. You will also get your legs involved with this particular variation. 

  1. Lie on your back, feet flat on the floor at hip-width apart and knees bent.
  2. Place your hands behind your ears.
  3. Engage your abs. 
  4. Lift your shoulder blades and feet off the floor until your lower legs are parallel to the floor, your knees at 90 degrees.
  5. Staying in this position, rotate your torso and bring your right elbow to your left knee while simultaneously extending your left leg out straight. 
  6. Switch sides and bring your left elbow to your right knee while simultaneously extending your right leg out straight. 
  7. Continue switching sides for the desired number of reps.

Note: Ensure you rotate your core and do not pull on your neck or head.

#3: Reverse Crunch 

This is an excellent crunch exercise if your neck tends to bother you while performing crunches because it stays on the ground for the duration of this particular movement. 

  1. Lie on your back, with your arms by your sides, or just under your glutes for more support.
  2. Engage your core.
  3. Bend your knees to 90 degrees and raise your legs so your knees are directly above your hips, lower legs parallel to the floor.
  4. Keeping your back flat on the floor, engage your core and bring your knees toward your chest, raising your hips off the floor and reaching your toes straight up toward the ceiling.
  5. Slowly bring your hips back down to the floor and your legs back to their starting position. 
  6. Repeat for the desired number of reps. 

Note: The further away you position your arms from your body, the more challenging the exercise will become.

#4: Scissor Crunch

With the scissor crunch, you will also engage your legs, mainly your quads and glutes.

  1. Lie on your back with your arms behind your head or by your sides and your legs extended. 
  2. Engage your core and lift your shoulder blades and legs off the floor. 
  3. Flutter” kick your legs as if you were swimming, keeping your core engaged at all times.
  4. Repeat for the desired amount of time.

For the following two variations, we have increased the difficulty by quite a bit, turning our basic isolation crunches into awesome compound crunch core exercises. 

Check them out for a total-body workout focused on the core: 

#5: Side Plank Crunch 

This exercise mixes a side plank and a crunch, where your entire body will be called on to work. You will need to use your balance, stability, and strength to master this one.

  1. Begin in a side elbow plank position with your feet stacked one on top of another and your upper arm stretched above you. 
  2. Bring the elbow from your extended arm and the knee of your top leg together in a crunch. 
  3. Return your arm and foot to their starting positions, trying not to rest the upper leg on the lower one but maintaining tension in your core and hovering over your lower foot.
  4. Repeat for the desired number of reps.
  5. Repeat on the other side. 

Now, that was a challenge, wasn’t it? 

Note: If your hips begin to sag during this side plank hold, adjust them and bring them back up in line with the rest of your body.

#6: Bird Dog Crunch 

Like our last crunch variation, we will be in a different starting position than our basic crunch.

  1. Begin on all fours in a tabletop position; your palms, knees, and toes are the points of contact with the ground.
  2. Lift your right foot and left hand off the ground and bring your right knee and left elbow together, crunching your core. 
  3. Then extend your right leg out in back of you and your left arm in front of you.
  4. Repeat this movement for the desired number of reps. 
  5. Repeat on the other side.

Note: Be sure to keep your body as solid as possible throughout the movement. Also, perform this movement slowly as it works your balance, stability, and strength all in one.

There you have it! The crunch exercise and some of its most popular variations that you can add to your workouts. If you are looking for even more core workouts, take a look at our plank guide, complete with step-by-step instructions and variations to try!

A scissor crunch.
Photo of author
Katelyn is an experienced ultra-marathoner and outdoor enthusiast with a passion for the trails. In the running community, she is known for her ear-to-ear smile, even under the toughest racing conditions. She is a UESCA-certified running coach and loves sharing her knowledge and experience to help people reach their goals and become the best runners they can be. Her biggest passion is to motivate others to hit the trails or road alongside her, have a blast, and run for fun!

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