In common parlance, the core of the body is broadly considered to be the torso. Functional movements are highly dependent on this part of the body, and lack of core muscular development can result in a predisposition to injury. The major muscles of the core reside in the area of the belly and the mid and lower back, and peripherally include the hips, the shoulders and the neck.
Core muscles are also involved in the Valsalva maneuver, where the thorax tightens while the breath is held to assist, often involuntarily, in activities such as lifting, pushing, excretion and birthing.
Anatomical posture and support
The core is traditionally assumed to originate most full-body functional movement, including most sports. In addition, the core determines to a large part a person's. In all, the human anatomy is built to take force upon the bones and direct autonomic force, through various joints, in the desired direction. The core muscles align the spine, ribs, and pelvis of a person to resist a specific force, whether static or dynamic.
An example of static core function is firing a rifle in the prone position. To maintain accuracy, the shooter must be able to transfer his or her own body weight and the weight of the rifle into the earth. Any attempt of the shooter to create a dynamic motion of the sights will result in a jerky posture where the sights do not sit still on the target. For the shooter to maintain accuracy, the muscles cannot exert force on the rifle, and the skeleton must be aligned to set the rifle onto the target. The core, while resting on the ground and relatively far away from the rifle, is nevertheless aligning the spine and pelvis to which the shoulder and arms and neck are connected. For these peripheral elements to remain static, and not move unnecessarily, the spine, pelvis, and rib cage must be aligned towards this end. Thus the core muscles provide support of the axial skeleton in an alignment where the upper body can provide a steady, solid base for the rifle to remain motionless.
Resistance: Gravity
Plane of movement: Coronal, Sagittal.
Dynamic core function
The nature of dynamic movement must take into account our skeletal structure in addition to the force of external resistance, and consequently incorporates a vastly different complex of muscles and joints versus a static position. Because of this functional design, during dynamic movement there is more dependence on core musculature than just skeletal rigidity as in a static situation. This is because the purpose of movement is not to resist a static, unchanging resistance, but to resist a force that changes its plane of motion. By incorporating movement, the bones of the body must absorb the resistance in a fluid manner, and thus tendons, ligaments, muscles, and innervation take on different responsibilities. These responsibilities include postural reactions to changes in speed, motion and power.
Example of dynamic core function
An example of this is walking on a slope. The body must resist gravity while moving in a direction, and balancing itself on uneven ground. This forces the body to align the bones in a way that balances the body while at the same time achieving momentum through pushing against the ground in the opposite direction of the desired movement. Initially, it may seem that the legs are the prime movers of this action, but without balance, the legs will only cause the person to fall over. Therefore, the prime mover of walking is achieving core stability, and then the legs move this stable core by using the leg muscles.
