Bodyweight or plate
Rotating the trunk side to side while seated leaned back trains the obliques in rotation.
| Muscle | Role | Action |
|---|---|---|
| External oblique | Primary | Rotates the trunk to the opposite side and bends it to the same side; compresses the abdomen |
| Internal oblique | Primary | Rotates and laterally flexes the trunk; compresses the abdomen |
| Rectus abdominis | Secondary | Flexes the trunk and braces the abdomen |
| Iliopsoas | Secondary | Flexes the hip and the trunk |
Primary muscles are the prime movers; secondary muscles assist or stabilise. The balance shifts with grip, stance, range of motion and technique.