CoreBW
A foundational FMS/Gray Cook drill teaching the core to keep the lumbar spine flat against the floor while opposite arm and leg move through space. Trains anti-extension control and contralateral limb coordination simultaneously — often the very first core drill taught to novice lifters.
Demo: Functional Movement Systems
Sets
3
Reps
8-10 per side
Rest
30s
Contraindications
None significant — this is often used as a low back pain rehab exercise itself (McGill, FMS).Setup
Lie on your back, hips and knees bent to 90 degrees, arms reaching straight up toward the ceiling.
Execution
- 1Press the low back flat into the floor and maintain that contact throughout
- 2Slowly extend one arm overhead and the opposite leg out straight
- 3Lower both just above the floor without letting the back arch
- 4Return to the start position with control
- 5Alternate sides for the set
Key cues
- Low back never leaves the floor
- Move slow, this isn't a race
- Exhale as the arm and leg extend
- Opposite arm, opposite leg
Common faults
- Low back arching off the floor as the limbs extend (most common fault)
- Moving too fast and losing control
- Extending the leg too low too soon
- Holding breath instead of exhaling on the extension
- Same-side arm and leg moving together instead of contralateral
Tweaks
- Reduce range of motion (only lower the leg, not the arm) as a regression
- Add a 2-second pause at full extension
- Progress to banded or weighted versions once mastered
Regressions
Progressions
Muscles
Primary: Transverse Abdominis, Rectus Abdominis
Secondary: Hip Flexors, Obliques
Notes
ANTI-EXTENSION. Difficulty 1 — the canonical entry-level core drill in the FMS system; widely prescribed by physical therapists and strength coaches alike.
Sources
Attribution: Gray Cook / FMS