Midline stabilization is essential for effective functional movement. Kelly Starrett, of San Francisco CrossFit, explains the essential anatomy and physiology of it in this excerpt from his one day seminar at CrossFit Santa Cruz on November 9, 2008.

The midline is the entire spine, and its stability is dependent not just on the core, but also on all the prime movers of the body, including the hip, glutes, and hamstrings. Excessive tightness in any of the prime movers will affect the core muscles, often resulting in low back pain.

In this part 6, Kelly explains that the hamstring is a two joint muscle, and must be treated from both ends (knee and hip). He shows a few tools to assess hamstring length. A shortened hamstring is a brake on full range movement. Extending the length of the hamstring removes that brake and improves performance.

This is the sixth of a series from Kelly on the theory and practice of stabilizing the midline in functional movement.

Watch this video in the CrossFit Journal here.