Bicycle crunches
Also called bicycle crunch, bike crunches, bicycle kicks.
What is a bicycle crunches?
A bicycle crunch is an alternating floor exercise that combines a trunk curl and rotation toward one bent knee while the opposite leg extends. It trains the internal and external obliques, with the rectus abdominis assisting. The torso rotation, not merely pedalling the legs, defines the exercise.
How do you perform a bicycle crunches?
Set up
- Lie on your back, bring your thighs up with the knees bent to about right angles, and curl your shoulders lightly off the floor.
- Place your fingertips beside your head without pulling the head forward.
Execution
- Extend one leg while rotating your rib cage toward the opposite bent knee.
- Return through the centre as the legs trade positions, then rotate toward the other knee.
- Continue alternating at a pace that keeps the pelvis controlled and the shoulders lifted.
Common mistakes
Pulling on the head
Rest the fingertips lightly and let the trunk produce the curl and rotation.
Moving only the elbow
Rotate the rib cage toward the opposite knee instead of flicking the arm across a still torso.
Pedalling too quickly
Slow down or keep the extending knee more bent if the pelvis rocks or the lower back lifts.
Where it fits in a session
Alongside other trunk exercises or in a bodyweight circuit.
Count either every side or each left-right pair as one rep, but use the same convention whenever you log it.
Muscles worked
Primary
Secondary
Schematic surface view. Some muscles are partly visible or not shown.
The torso alternates rotation and flexion. The hip flexors also move the legs, but they are not promoted to a target on one exact source alone.
Variations
- Standing bicycle crunch — Alternates a standing knee lift and trunk rotation without the floor setup.
- Twisting crunch — Keeps both feet supported and rotates the trunk during an ordinary crunch.
Frequently asked questions
Does the elbow have to touch the knee?
No. Rotate the rib cage toward the opposite knee without forcing contact or pulling the head forward.
How do I count bicycle crunches?
You can count each side or count a complete left-right pair. Pick one convention and keep it consistent in your training log.
What if extending the leg makes my back arch?
Keep the knee more bent or shorten the reach until the pelvis stays controlled throughout the alternating movement.