BOSU Lateral Crunch

Target muscles

The internal and external obliques drive the side-bend, with the quadratus lumborum assisting on the working side. Draping the torso over the dome lengthens those lateral fibres at the bottom, so they contract from a deep stretch up to a hard shortened squeeze. The rectus abdominis stabilises throughout.

How to perform

Setup

Lie sideways with the side of your hip and lower ribs on the dome, legs stacked or staggered with the feet braced against a wall or heavy object. Place your top hand behind your ear and let your bottom arm rest on the floor for light support.

Execution

Crunch your top elbow toward your top hip, bending the spine laterally and lifting your ribcage off the dome. Squeeze the working obliques hard at the top, then lower slowly until your trunk wraps the BOSU and you feel a clear stretch down the side. Complete all reps on one side before switching. Keep the motion purely sideways — no twisting toward the floor.

Common mistakes

• Rotating the torso instead of bending it directly to the side, which turns it into a twist and dilutes the oblique work.
• Letting the hips roll forward or back so the base becomes unstable and the lift loses its line.
• Pulling on the neck with the top hand to muscle the rep up.
• Cutting the bottom range short and skipping the stretched position where most of the value lives.

Progressions and regressions

Regress to a floor-based side crunch if balancing on the dome throws off your line. Progress by holding a light dumbbell against the top shoulder, adding a pause at the top, or slowing the lowering phase to four seconds. Keep load light — the obliques respond to range and control, not heavy weight here.

Programming notes

Program it as oblique accessory work, 2-3 sets of 12-15 per side, balanced left and right. It slots in nicely on a core day next to an anti-rotation movement so you cover side flexion and rotary stability in the same block. Keep reps even on both sides to avoid building a lateral imbalance.