The core or trunk is the axial (central) part of an

organism In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and ...

body Body may refer to: In science * Physical body, an object in physics that represents a large amount, has mass or takes up space * Body (biology), the physical material of an organism * Body plan, the physical features shared by a group of anima ...

. In common parlance, the term is broadly considered to be synonymous with the

torso The torso or trunk is an anatomical term for the central part, or the core, of the body of many animals (including humans), from which the head, neck, limbs, tail and other appendages extend. The tetrapod torso — including that of a huma ...

, but academically it also includes the head and neck. 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 (not the shoulders), and peripherally include the hips, the shoulders and the neck.

Muscles

Major muscles included are the

pelvic floor The pelvic floor or pelvic diaphragm is composed of muscle fibers of the levator ani, the coccygeus muscle, and associated connective tissue which span the area underneath the pelvis. The pelvic diaphragm is a muscular partition formed by the lev ...

muscles,

transversus abdominis The transverse abdominal muscle (TVA), also known as the transverse abdominis, transversalis muscle and transversus abdominis muscle, is a muscle layer of the anterior and lateral (front and side) abdominal wall which is deep to (layered below) t ...

multifidus The multifidus (multifidus spinae : ''pl. multifidi'' ) muscle consists of a number of fleshy and tendinous fasciculi, which fill up the groove on either side of the spinous processes of the vertebrae, from the sacrum to the axis. While very th ...

internal Internal may refer to: *Internality as a concept in behavioural economics *Neijia, internal styles of Chinese martial arts *Neigong or "internal skills", a type of exercise in meditation associated with Daoism *''Internal (album)'' by Safia, 2016 ...

and

external oblique The abdominal external oblique muscle (also external oblique muscle, or exterior oblique) is the largest and outermost of the three flat abdominal muscles of the lateral anterior abdomen. Structure The external oblique is situated on the lateral ...

rectus abdominis The rectus abdominis muscle, ( la, straight abdominal) also known as the "abdominal muscle" or simply the "abs", is a paired straight muscle. It is a paired muscle, separated by a midline band of connective tissue called the linea alba. It exte ...

, erector spinae (sacrospinalis) especially the

longissimus thoracis The longissimus ( la, the longest one) is the muscle lateral to the semispinalis muscles. It is the longest subdivision of the erector spinae muscles that extends forward into the transverse processes of the posterior cervical vertebrae. Stru ...

, and the diaphragm. The lumbar muscles, quadratus Lumborum (deep portion), deep rotators, as well as cervical muscles, rectus capitus anterior and lateralis, longus coli may also be considered members of the core group. Minor core muscles include the latissimus dorsi, gluteus maximus, and

trapezius The trapezius is a large paired trapezoid-shaped surface muscle that extends longitudinally from the occipital bone to the lower thoracic vertebrae of the spine and laterally to the spine of the scapula. It moves the scapula and supports th ...

Functions of the core

The core is used to stabilize the thorax and the pelvis during dynamic movement and it also provides internal pressure to expel substances (vomit, feces, carbon-laden air, etc.). *Continence :Continence is the ability to withhold bowel movements, and urinary stress incontinence (the lack of bladder control due to

dysfunction) can result from weak core musculature. *Pregnancy :Core muscles, specifically the

, are used during labor and delivery. *Valsalva maneuver :Core muscles are also involved in the

Valsalva maneuver The Valsalva maneuver is performed by a forceful attempt of exhalation against a closed airway, usually done by closing one's mouth and pinching one's nose shut while expelling air out as if blowing up a balloon. Variations of the maneuver can ...

, where the

thorax The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the cre ...

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

posture Posture or posturing may refer to: Medicine * Human position ** Abnormal posturing, in neurotrauma ** Spinal posture ** List of human positions * Posturography Posturography is the technique used to quantify postural control in upright stance in ...

. 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 The rib cage, as an enclosure that comprises the ribs, vertebral column and sternum in the thorax of most vertebrates, protects vital organs such as the heart, lungs and great vessels. The sternum, together known as the thoracic cage, is a semi- ...

, and pelvis of a person to resist a specific force, whether static or dynamic. Guide to building a strong core
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Static core function

Static core functionality is the ability of one's core to align the skeleton to resist a force that does not change. Medicine Ball Plank

= Example of static core function

= An example of static core function is firing a rifle in the

prone position Prone position () is a body position in which the person lies flat with the chest down and the back up. In anatomical terms of location, the dorsal side is up, and the ventral side is down. The supine position is the 180° contrast. Etymolo ...

. To maintain accuracy, the shooter must be able to transfer their body weight and the weight of the rifle into the earth. Any attempt of the shooter to create a dynamic motion of the sights (muscle the sights onto the target vs. allowing the posture to aim) 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 (and therefore the sights) 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 The axial skeleton is the part of the skeleton that consists of the bones of the head and trunk of a vertebrate. In the human skeleton, it consists of 80 bones and is composed of six parts; the skull (22 bones), also the ossicles of the middle ...

(skull, spine, and tailbone) 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 (side to side), Sagittal (forward and behind the anatomical position). Human anatomy planes, labeled

Dynamic core function

The nature of dynamic movement must take into account our skeletal structure (as a lever) 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 the 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 (quickness of a contraction), motion (reaction time of a contraction), and power (amount of resistance resisted in a period of time).

= 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.