BOSU Bicycle Crunch
A rotating bicycle crunch on the BOSU dome that loads the obliques and lower abs while the unstable base keeps the core working.
Level: Beginner
Primary: Abs
Movement: Isolation
Tags: Balance / Stability Rotational
Type: Strength (Weight Lifting)
Equipment: Balance Trainer
Target muscles
The rectus abdominis drives the curl while the internal and external obliques produce the elbow-to-opposite-knee rotation. Draping the lower back over the dome lets the spine extend slightly below flat at the bottom, so the abs are loaded through a longer arc than on the floor. The hip flexors carry the cycling legs and the deep transverse abdominis braces continuously to stop you rolling off the side.
How to perform
Setup
Sit on the centre of the dome and walk your hips back until your lumbar spine wraps the BOSU. Plant your feet, lift them to a tabletop position, and cup your hands lightly behind your ears without lacing the fingers. Pin your lower back into the dome before the first rep.
Execution
Exhale and curl your right shoulder toward your left knee as that knee draws in and the right leg extends long and low. Lead with the shoulder, not the elbow, so the rotation comes from the trunk rather than a flapping arm. Pause when your shoulder blade clears the dome, then switch sides in one continuous pedalling rhythm. Keep the tempo deliberate — a slow cycle keeps tension on the obliques where a fast one turns into momentum.
Common mistakes
- Yanking on the head and craning the neck instead of rotating from the trunk.
- Pedalling so fast the movement becomes momentum with no real spinal flexion.
- Letting the extended leg drop and arch the lower back off the dome.
- Rotating only the elbow across while the shoulders stay flat on the surface.
Progressions and regressions
Regress by keeping the extending leg higher and slower, or by performing the move on the floor until the balance demand settles. Progress by lowering the working leg closer to the dome for a longer lever, adding a two-second pause at each rotation, or holding a light plate across the chest.
Programming notes
Use it as oblique-focused accessory work near the end of a session, 2-3 sets of 12-20 reps per side. The unstable base makes sloppy high-rep grinding pointless, so stop while each rotation still reaches full range. It pairs naturally with an anti-rotation hold to round out the trunk's twisting and bracing roles.
