BOSU Crossover Crunch

Target muscles

The obliques are the focus here, twisting the ribcage toward the opposite hip while the rectus abdominis flexes the spine. Wrapping the lower back over the dome lengthens the abdominal wall at the bottom, so the crossover starts from a stretched, loaded position rather than a slack one. The transverse abdominis braces to keep you balanced on the curved surface throughout.

How to perform

Setup

Drape your lower back over the centre of the dome with feet planted hip-width. Bring one ankle up to rest across the opposite knee in a figure-four, and place the hand on the working side lightly behind your head with the elbow wide.

Execution

Exhale and curl that elbow up and across toward the raised knee, rotating through the waist rather than just poking the elbow forward. Feel the oblique on the working side shorten as your shoulder blade lifts off the dome. Pause at the top, then lower slowly until your back wraps the dome again and the abs re-lengthen. Complete your reps on one side or alternate, keeping the motion controlled so the twist comes from the trunk.

Common mistakes

• Pulling the head with the hand and straining the neck instead of rotating the torso.
• Throwing the elbow across with momentum rather than curling and twisting the ribcage.
• Sitting too far back so the hips, not the spine, do the work.
• Skipping the full lower-down that gives the oblique its stretch.

Progressions and regressions

Regress to a floor crossover crunch or reduce the range until balance is comfortable. Progress by adding a pause at peak contraction, holding a light plate to the working shoulder, or extending the bottom leg straight for a longer lever.

Programming notes

Slot it in as oblique accessory work, 2-3 sets of 12-15 reps per side, late in a session after the heavy compounds. Keep the load light and the reps clean — the obliques respond to controlled range, not to hauling. Pair it with a direct rectus-abdominis move and an anti-rotation hold for balanced trunk training.