Air Bike
The air bike — the bicycle crunch — pedals your legs while you rotate elbow toward opposite knee. It is the rare bodyweight ab movement that trains flexion and rotation in the same rep, and its whole value depends on going slowly enough that the obliques, not momentum, move you.
Own the movement
Set up first, then execute. Every cue below is something you can check on your next set.
Before the first rep
- Lie on your back and press your lower back flat into the floor before you lift anything. That contact is the standard for the whole set.
- Rest your fingertips lightly behind your ears. Do not lace your fingers behind your head — that is where the neck pulling starts.
- Lift both feet so your knees stack over your hips and your shins sit parallel to the floor.
- Curl your shoulder blades off the floor and keep them off for every rep of the set, not just the crunching one.
Every rep
Breathing & tempo — Exhale as you rotate and reach, inhale as you switch sides. Roughly a two-second count each way, with a brief hold at the top of each twist.
Sets, reps & load
Where to start, and what to change when it stops being hard.
Bodyweight only. Progress by lowering the extended leg closer to the floor and by adding a one-second pause at each twist rather than by chasing rep counts. When 20 slow reps per side stop being difficult, move to a loaded or hanging movement instead of extending the set past two minutes.
What goes wrong
The errors that show up most often, and the cue that fixes each one.
Rest fingertips behind the ears and keep a fist-sized gap between chin and chest. If you cannot reach without pulling, stop rotating so far and shorten the range.
Slow to roughly two seconds per side with a pause at the twist. Cut the rep target in half; you will find it harder than the fast version was.
Raise the angle of the extended leg until your back stays down. Lower it a few degrees each session as your control improves.
Stay curled up for the whole set. The upper abs should be under continuous tension from the first rep to the last.
Why bother
Two things happen at once here. The extended leg pulls your pelvis into an anterior tilt, so the lower abs have to fight to keep your lower back pressed into the floor, while the twist toward the bent knee loads the obliques on the opposite side. Most crunch variations give you one of those; this gives you both, which is why it is worth keeping despite how often it is done badly.
Speed destroys it. Done fast, the rotation comes from throwing the elbow and the legs cycle on momentum, and the set becomes a mildly out-of-breath arm swing. Done at roughly two seconds per side, with the shoulder blade actually leaving the floor, twenty reps is genuinely hard.
Where it fits
End of a session, two or three times a week, alongside an anti-extension movement like a rollout or a plank. It needs no equipment and no floor space beyond your own length, which makes it a reasonable choice for travel or home training when a cable stack is not available.
If this one isn't it
No kit, too hard, or too easy — here's where to go instead.
Same job, different kit
Start here instead
When this gets easy
Asked and answered
Is the bicycle crunch really the best ab exercise?
That claim comes from a small EMG study, and EMG measures muscle activation over a few reps, not growth or strength over months. It is a good movement because it combines flexion and rotation cheaply, but it will never load your abs the way a weighted crunch or a rollout does. Use it alongside those, not instead of them.
Will this burn the fat off my waist?
No. Spot reduction is not a thing — where you lose fat is decided by genetics and overall energy balance, not by which muscle you train. Air bikes build the obliques and deep flexors; whether you can see them is settled in the kitchen and by your total training volume.
How low should the extended leg go?
As low as you can hold while your lower back stays pressed into the floor. For most people starting out that is around 45 degrees; with practice it comes down toward 20-30 degrees. The moment your back arches, you have handed the work to your hip flexors.
My hip flexors get tired before my abs. What is wrong?
Usually nothing is wrong — the psoas works hard in any leg-extension movement. But if the burn is entirely in the front of your hips, you are likely swinging the legs and not curling the ribcage toward the pelvis. Focus on the rotation and the shoulder blade lift, and keep the legs slower and higher.