The best teachers can simplify the most complex concepts, and Coach Greg Glassman always did so by including a session at the whiteboard before workouts at the original CrossFit gym in Santa Cruz.
Back in front of the board, Coach Glassman and Tony Budding discuss the basic concepts that hold up CrossFit’s definition of core strength. A line—the midline—can be drawn through the integration of the pelvis and the spine, and this line is profoundly important to functional movement.
“Lack of movement around that line while engaged in functional movement is core strength,” Coach explains.
All the movements in the CrossFit protocol have an immense impact on the midline, and using these functional movements is one reasonable measure of core strength. Midline stability allows success when performing functional movements, and increased capacity in those movements therefore should indicate an increase in core strength.
Additional reading: The Moves by Greg Glassman, published April 1, 2004.