Name of Exercise —Bent knee sit-up

Type of Exercise —Multi-joint

Muscles Used —Abdominals

Starting Position

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  • Lie face up on an exercise mat.
  • Bend your knees so that your feet are flat on the floor, or put your lower legs up on a bench while maintaining a 90° angle at the hip and knee.
  • Place your arms across your chest or down at your sides.

Upward Movement

  • Lift your head off the floor but avoid pulling yourself up by your neck.
  • Curl your upper body off the floor toward your thighs until your upper back is off the floor.
  • Exhale during the upward movement.

Downward Movement

  • Lower your shoulders down in a controlled manner while keeping your feet on the floor or your lower legs on the bench.
  • Inhale during the downward movement.

Trainer Tip

It is important to perform a posterior pelvic tilt prior to performing the crunch. To do this, press your lower back into the floor while curling your pelvis slightly upward. This will engage your abdominal muscles from the start and make the movement more efficient. Place your hands across your chest or down at your sides rather than behind your head.


National Association for Health and Fitness

President's Council on Fitness, Sport & Nutrition


Canadian Society for Exercise Physiology

Health Canada Physical Activity


10 steps to perfect sit-ups. HubPages website. Available at: Updated April 23, 2013. Accessed August 8, 2016.

Bent-knee sit-up/crunches. American Council on Exercise website. Available at: Accessed August 8, 2016.

Last reviewed August 2016 by Michael Woods, MD  Last Updated: 8/8/2016