Core · Spinal flexion
Bicycle Crunches
The bicycle crunch is a floor exercise where you alternate bringing each elbow towards the opposite knee while cycling your legs. It combines spinal flexion with rotation, so it trains the rectus abdominis and the obliques together, and it consistently ranks near the top of abdominal activation comparisons.
Also known as: Bicycle crunch, Air bike, Cross-body crunch
- Muscle group
- Core
- Movement pattern
- Spinal flexion
- Type
- Isolation
- Equipment
- Bodyweight
- Difficulty
- Beginner
What muscles does the bicycle crunches work?
Primary movers
- Rectus abdominis
- Obliques
Assisting muscles
- Hip flexors
- Transverse abdominis
Two actions are combined here. The rectus abdominis flexes the spine, pulling the ribcage towards the pelvis, and the obliques rotate the trunk so one shoulder travels towards the opposite knee. Most ab exercises train one or the other, not both.
The internal oblique on one side and the external oblique on the other work together to produce each rotation. That pairing is why the movement alternates: each side gets its turn as the rotating side and then as the resisting side.
A frequently cited study from the American Council on Exercise found bicycle crunches produced the highest rectus abdominis activation of the thirteen exercises it tested. That finding is often overstated, since activation is not the same as growth, but it does indicate the exercise loads the abs meaningfully.
The hip flexors are more involved than in a standard crunch, because the legs are cycling in the air rather than resting on the floor. This is part of why the exercise fatigues quickly, and part of why letting the legs drop too low makes the lower back the limiting factor.
The transverse abdominis works throughout to keep the pelvis and ribcage connected while the legs move. Keeping the lower back in contact with the floor is the practical sign that it is doing its job.
How to do the bicycle crunches
Setup
- 1
Lie on your back with your hands lightly touching the sides of your head, fingertips only.
- 2
Lift both feet off the floor with knees bent to about 90 degrees.
- 3
Press your lower back into the floor and exhale to bring your ribs down.
- 4
Lift your head and shoulder blades slightly off the floor before starting.
- 5
Keep your elbows wide rather than pulled in towards each other.
Execution
- 1
Rotate your torso to bring one shoulder towards the opposite knee as that knee draws in.
- 2
Extend the other leg out straight at the same time, keeping it above the floor.
- 3
Turn from the ribcage rather than yanking the elbow across. The shoulder should travel, not just the arm.
- 4
Pause briefly at the point of full rotation before switching sides.
- 5
Switch smoothly to the other side, keeping both shoulder blades off the floor throughout.
- 6
Keep the extended leg high enough that your lower back stays pressed into the floor.
Common bicycle crunches mistakes
Pulling on the head and neck
Lacing the fingers behind the head and hauling on it to rotate, which strains the neck and lets the arms do work the abs should be doing.
The fix: Rest your fingertips lightly at the sides of your head, with your thumbs behind your ears. If your hands are pulling, uncross them and put them across your chest instead.
Cycling too fast
Racing through reps so momentum carries the legs and torso. It raises the heart rate and lowers the work the abs actually do.
The fix: Slow down and pause at the top of each rotation. Twenty controlled reps beat sixty rushed ones, and the difference is obvious within a set.
Dropping the extended leg too low
Letting the straight leg approach the floor when the abs cannot hold the pelvis, which pulls the lower back into an arch and shifts load onto the hip flexors and lumbar spine.
The fix: Keep the leg higher. The correct height is the lowest point at which your lower back is still touching the floor, and it rises as you fatigue.
Moving only the elbow
Swinging the arm across the body without rotating the torso, so the obliques barely engage and the rep becomes an arm movement.
The fix: Think about bringing the shoulder and ribcage towards the knee. The elbow arrives because the torso turned, not the other way round.
How many sets and reps?
| Goal | Sets | Reps | Load | Rest |
|---|---|---|---|---|
| Hypertrophy | 3 | 10–15 per side | Bodyweight, slow tempo | 45–60 s |
| Endurance | 3 | 30–45 s | Bodyweight | 30–45 s |
| Circuit finisher | 2–3 | 20 per side | Bodyweight | 30 s |
Bicycle crunches are a good general ab exercise and need no equipment, which makes them easy to keep in a programme. Three sets of 10–15 slow reps per side, two or three times a week, is enough. The main thing that undermines them is speed, so if you find yourself doing sets of fifty, slow the tempo rather than adding reps. They pair well with an anti-extension exercise like the plank or dead bug, since those cover the bracing function that this exercise does not.
Running the bicycle crunches in your next block? Hercules logs every set, shows last session's numbers before you lift, and suggests when to add weight.
Get it on Google PlayBicycle Crunches variations and alternatives
Crunches
EasierRemoves the rotation and the leg movement, leaving straightforward spinal flexion. A sensible starting point.
Slow Tempo Bicycle Crunch
HarderThree seconds per rep with a pause at full rotation. Far harder than it sounds and the most useful way to progress without equipment.
Russian Twist
AlternativeTrains trunk rotation from a seated position and is easy to load with a plate or medicine ball.
Hanging Leg Raise
HarderA substantially harder movement that loads the lower portion of the abs through a longer range.
Side Plank
AlternativeTrains the obliques isometrically to resist side bending rather than to produce rotation. Complementary work.
Frequently asked questions
Are bicycle crunches good for abs?
Yes. They combine spinal flexion with rotation, so the rectus abdominis and obliques are trained in one movement, and they need no equipment. A widely cited ACE study ranked them highest for rectus abdominis activation among the exercises tested, though that is one measure and not a guarantee of superior growth.
How many bicycle crunches should I do?
Three sets of 10–15 slow reps per side is a reasonable target. If you can do far more than that, the reps are almost certainly too fast. Slowing the tempo and pausing at full rotation makes the same rep count considerably more demanding.
Do bicycle crunches burn belly fat?
No. Fat loss comes from an overall energy deficit, and it is not possible to direct it to a particular area by training the muscle underneath. Bicycle crunches build the abdominal muscles, which is what becomes visible once body fat is low enough.
Why does my neck hurt during bicycle crunches?
Almost always because you are pulling on your head with your hands. Keep your fingertips resting lightly behind your ears and lead with the ribcage, not the elbow. If it persists, crossing your arms over your chest removes the option of pulling entirely.
Should my legs touch the floor?
No. The extended leg should stay above the floor throughout, and high enough that your lower back stays pressed down. Lower is harder, but only up to the point where the back lifts. Past that you are training your hip flexors and loading your lumbar spine instead.
Hercules tracks every bicycle crunches you log, shows you last session's numbers before you lift, and flags when your progress stalls.
Get it on Google Play