Plank With One Knee Bent

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Plank with one knee bent

Try plank with one knee bent if planking or other ab exercises cause soreness or discomfort in your lower back. This exercise allows to strengthen the abdominal muscles while avoiding hurting the lower back.

You see, very often when training abs hip flexors kick in and do the job your abs are supposed to do. Once hip flexors start to dominate the ab exercise it can cause lower back pain. That’s because muscle like Psoas Major that starts in the upper front leg and attaches to the spine gets too tight and pulls lumbar vertebrae.

To avoid this from happening take the hip flexors out of the equation by bending the knee. It really helps to take the strain of the hip flexors thus eliminating the lower back pain and a chance to hurt the low back.

Recommended For You If…

  • You feel a discomfort in your lower back when performing regular plank variations or other abs exercises.
  • Your lower back gets sore before your abs do when you do train them.
  • You have tight hip flexors.
  • You have weak abdominal muscles.
  • You have an anterior pelvic tilt (aka “Donald Duck” butt)
Main Target: All abdominal area.
Equipment needed: None.

How To Do Plank With One Knee Bent Correctly

Similarly to the other plank variations this one is very easy to screw up as well. If your back gets sore or hurts when planking more likely your form needs to be improved. To do plank with one knee bent with a correct technique follow the description below.

STEP 1: First get in a regular plank position with your forearms on the floor.

To do so lay down on a floor. Place your elbows directly below the shoulders and ground your toes into the floor. Lift your body from the floor and form a straight line. Contract your ab muscles so hard as Bruce Lee was going to punch you in the guts.

STEP 2: Then simply bend one leg and place the knee on the floor. Nothing else moves or changes. Now hold the position as long as you can without compromising the perfect form.

Once your form start to suffer, know that your abdominal muscles have used all their strength and a lot of pressure goes to your lower back. That’s the moment when to stop the exercise to avoid hurting your lower back.

Still Feel It In Your Lower Back?

If you still feel the strain or discomfort in your lower back when performing plank with one knee bent then put both knees on the floor. This will reduce the tension in the lumbar spine region while still leaving enough work for your abs to do.


  • Perform the exercise next to the mirror so you can see your form.
  • Alternate the knee you bend on each set or in the middle of the exercise.
  • Draw in the navel and breathe deeply through the belly.
  • Once you master this exercise try Bench Plank or regular Plank on forearms.

Common Mistakes:

  • arching and rounding the back.
  • lifting the butt up too high.
  • looking around.
  • Pushing past the lower back pain.
  • Elbows not aligned directly below the shoulders.
  • Sagging in shoulders.
About Matiss Bartulis

Sweets and pizza addict. Online and real-life fitness coach. Author of the "From Fat To Six Pack" E-mail training course. You can find him on Google+ and Facebook.