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Knee In and Out Crunch

Step by step instructions, muscle activation and variants for the Knee In and Out Crunch.

EasyAbs

About this exercise

A floor abdominal exercise that combines a crunching motion with simultaneous knee-tuck movements, creating constant tension through the entire core. Drawing the knees in and extending them out while crunching activates the rectus abdominis and hip flexors together in a coordinated, rhythmic movement.

How to Perform

  • Lie flat on your back with hands lightly behind your head or at your temples and legs extended
  • Lift your shoulder blades off the floor, keeping your lower back pressed into the ground
  • Simultaneously draw both knees toward your chest while crunching your torso forward
  • Briefly pause when your knees are near your chest and elbows near your knees
  • Extend both legs back out to the starting position while lowering your torso slightly — but do not let your shoulders or feet touch the floor
  • Repeat the crunch-and-draw motion continuously in a controlled rhythm
  • Breathe out as you crunch in and breathe in as you extend out

Muscle Activation

Primary
Abs
Secondary
CoreObliques

About the Knee In and Out Crunch

The Knee In and Out Crunch is a foundational movement that builds strength and muscle through controlled, progressive overload. Train it 1 to 2 times per week with 3 to 5 working sets per session, gradually adding weight or reps as form holds up.

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