How to Do Knee Crunches

Method 1

Method 1 of 3:

Doing an Elbow-to-Knee Crunch

For the sake of comfort, lie on a carpeted section of floor or on a yoga mat. Bend your legs and draw up your knees until they’re directly over your pelvis. Bend your knees at a 90-degree angle so that your feet are sticking straight out.^{[1] X Research source}
This style of elbow-to-knee crunches are great to use if you’re a beginner to fitness and exercising. They’ll build up your abdominal muscles but aren’t particularly challenging to learn.

To get your torso into position for elbow-to-knee crunches, stretch your arms up behind you. Then, bend your elbows and hold both hands behind your head. Bend your neck so that you are looking down your body towards your belly button.^{[2] X Research source}
Try interlocking your fingers behind your head to support your head and keep your hands in place.

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Keep your chin down and tense your abdominal muscles. Keep your abs activated the whole time while you're doing the exercise.^{[3] X Expert Source Dean Theriot
Personal Trainer Expert Interview. 22 January 2021.} To do a crunch, keep your elbows in place and lift your knees upward until your elbows and knees touch. You should feel a slight burn in your lower abs as you touch your elbows and knees together.^{[4] X Research source}
Make sure that you’re engaging your stomach muscles and not just pulling on your head with your hands. You can damage your neck if you pull your head up rather than using your abdominal muscles.

After you’ve completed 1 crunch, slowly relax your abdominal muscles and lower your head back down to the ground. Also lower your knees until they’re again directly above your pelvis.^{[5] X Research source}
Relaxing your body slowly will keep your abdominal muscles engaged for longer than they would be if you quickly relaxed your muscles.

After laying back flat on the ground, again clench your abdominals and bring your knees up to your elbows. Complete 9 more crunches in a row to do a set of 10. If you’re just starting out and don’t have very strong abdominal muscles, 1 full set might be as much as you can do. As you gain muscle, try completing 2, 3, or even 4 sets.^{[6] X Research source}
Take a 60-second break between each set of crunches to allow blood and oxygen to return to your abs.

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Method 2

Method 2 of 3:

Performing Knee Pull Crunches

Interlace the fingers of your hands and place them behind your head. Lie back on a soft, flat surface like a yoga mat or carpeted section of flooring. Extend both legs in front of you and cross your right ankle over your left.
Wear flexible clothing while doing knee pull crunches. For example, yoga pants or sweat pants would work well.

Engage your abs and bring your head up so you’re looking down at your stomach. Separate your legs (don’t keep your knees together) and bring both knees up until they’re almost touching your chest. Hold the pose for 3–5 seconds and then relax back to your starting pose. This is a great workout for your lower core.^{[7] X Research source}
Unlike elbow-to-knee crunches, your elbows and knees do not touch each other during knee pull crunches.

Begin each crunch from your starting position: flat on your back with ankles crossed. Tense your abs, keep your legs apart, and draw your knees up to your chest. As your perform the crunches, you should feel the burn in your lower abs and core muscles. Give yourself at least 1–2 minutes between each set of crunches so your muscles can relax.
If you’re new to fitness and exercise, you may find that you can only manage to do 1 full set at first.

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Method 3

Method 3 of 3:

Doing Cross-Body Crunches

Do this on a surface that won’t hurt your back, like a yoga mat or a bed. Interlace your fingers and use both hands to support your head. This exercise is a variation on the standard knee crunch and works your obliques more than other varieties of knee crunches do.^{[8] X Research source}
Your obliques are part of your abdominal muscles. They’re located on the outer sides of your torso and run from your waist to just under your armpits.

Lift up your knees so that your legs are bent at a 90-degree angle at your hips. Extend your lower legs out in front of you so that your calves are parallel to the ground and your feet are in midair.^{[9] X Research source}
This is the starting position from which you’ll begin doing crunches. You’ll also return to this position after every crunch.

Bend your left knee so that your calf and thigh touch and fully extend your right leg. Flex your abdominal muscles and bring your left knee up to touch your right elbow. Keep your shoulders low to the ground as you’re bringing your knee to your elbow, so that all of the work is being done by your abs and core muscles. Hold the crunch for 2–3 seconds.^{[10] X Research source}

Return to your starting pose after touching the knee to the elbow.

Keep your lower back pressed flat against the ground. You shouldn't have any space between your lower back and the floor.^{[11] X Expert Source Dean Theriot
Personal Trainer Expert Interview. 22 January 2021.}

This time, bend your right knee and bring it up towards your chest. Fully extend your left leg. Flex your abs and rotate your core to the right so that your left elbow touches your right knee. Hold the crunch for 2–3 seconds and then return to the starting pose.^{[12] X Research source}

You should feel a slight burn on your sides as your perform the crunches.

Try performing 10 crunches in a row. To give your obliques a good workout, do 2 or 3 sets of 10 crunches each.^{[13] X Research source}

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