How does this differ from a standard bicycle crunch?

The splinter sit-up utilizes a larger range of motion by bringing the torso higher off the ground and starting from a dead-stop flat position. This increases the demand on the hip flexors and the entire abdominal wall compared to the rapid cadence of bicycle crunches.

Is this exercise safe for people with lower back pain?

Individuals with active lower back issues should proceed with caution as the movement involves significant spinal flexion and rotation. Focus on keeping the eccentric phase slow and ensure the lumbar spine is supported by the floor at the start of every rep.

How many repetitions should I perform for core definition?

Aim for 12 to 15 controlled repetitions per side. Quality of contraction and rotational depth are more important than high volume for targeting the external obliques effectively.

Splinter Sit-ups Guide | Oblique Rotation Technique

Master the splinter sit-up with our expert guide. Learn the proper form to target your obliques and build a stronger, more stable core.

How to Perform

Lie flat on your back on a firm surface with your legs extended straight and arms resting at your sides.
Engage your core to lift your upper back off the floor while simultaneously pulling one knee toward your chest.
Rotate your torso to bring the opposite elbow toward the rising knee, meeting in a controlled crunch at the center of the movement.
Squeeze your obliques at the peak of the contraction for one second while maintaining a neutral neck position.
Lower your leg and torso back to the starting position with control, ensuring your lower back remains pressed against the floor.
Repeat the motion on the opposite side to complete one full repetition.

Common Mistakes

Pulling on the back of the neck during the upward phase
Using momentum or swinging the legs to lift the torso
Allowing the lower back to arch off the floor
Rushing through the rotation without a full contraction

Muscles Worked

Primary movers

Obliquus externus abdominis

Stabilizers

Rectus abdominis
Iliopsoas
Transverse abdominis

Related Guides

3008 Abdominal Crunch — Core
Ab Roller — Core
Ab wheel — Core

Obliquus externus abdominis · Core