This is an excerpt from Winning Jumps and Pole Vault by Ed Jacoby.
Core Strength and Stabilization
The human body is a unique structure. The skeletal system provides support and a point of origin and insertion for muscles. Yet despite its strength, the skeleton would collapse into a useless pile of bones if the muscles and connective tissues were not providing support and stability. Just standing in place requires a great deal of stability within the system. Imagine the stability needed when sprinting and then jumping!
The pelvic girdle is the critical stabilizing joint. The pelvis can rotate somewhat freely both forward and back and side to side. Without stabilization of the pelvic girdle during sprinting, the hip flexors would pull the pelvis forward, thus limiting knee lift and range of motion. This, in effect, would minimize elastic force generation, which is critical to running at high velocity.
Posture is also related to stability and has a direct bearing on movement efficiency. Both general posture and dynamic posture must be addressed on a daily basis when training elements that build stability in the system. Core, or pillar, training is a primary way to do this. The exercises in this section should be done at some level every day. They can be done at the beginning or end of the session. The load can be increased by increasing the number of repetitions or the amount of time.