I wrote this a while ago, Some of the sports flexibility theory may have changed.
Core Muscles , The Basics
Muscles and Muscular Design,
Allot of muscles play a role in the core of the body, for this purpose we will divide the body into sections and list the appropriate muscles present.
Posterior Aspect of the Core ((The Shoulders, The Upper Back, The Lower Back))
Trapezius Muscles --
Where -- Connected to the base of the skull, down the Cervical and a majority of the thoracic vertebrae in the spine, it also comes across and connects to the Clavicle and Scapula, being on the external aspect of the body, also referred to as the superficial aspect.
This muscle is present in a pair one either side of the spine, connected at the centre by ligaments combining either side of the Vertebrae.
What -- This muscle is responsible for lifting the Clavicle, pulling the head backwards and supporting the shoulder against the pull of the pectorals.
Appearance -- When thickened or built in size it tends to raise the inner edge of the shoulders and give the neck a more triangular appearance commonly seen in weight lifters.
Deltoid Muscles --
Where -- Connecting to the Clavicle and Scapula it comes down over the top of the shoulder joint and sweeps down to a point connecting to the Humerus beyond the shoulder joint again this is an external or "superficial" muscle.
This muscle comes in a pair one covering the upper side of either shoulder joint, both are isolated from each other and don't effect each other due to the spacing between them.
What -- This muscle is responsible for Abduction of the arm and also draws the arm and shoulder back and forwards. However in relation to the core the deltoid plays a role balancing the pull of several core muscles on the shoulder joints.
Appearance -- A large bulb on top of the shoulder giving it a rounded shape, easily visible as it is built in size.
Infraspinalis Muscles --
Where -- Connecting to the bottom of the Scapula and sweeping up along the back of the Scapula to the shoulder, passing under the Deltoid and connecting to the Humerus. This is an Interior or Deep muscle, which is under the Trapezius.
This muscle comes in a pair, one either side of the back covering the base of either scapula and attaching to either arm, they do not connect along the centre-line of the body.
What -- This muscle is responsible for Lateral Rotation of the Humerus and Adduction of the arm. However in relation to the core the Infraspinalis plays a role in balancing the pull of muscles on the Scapula and shoulder.
Appearance -- Due to being a "Deep" or Interior aspect muscle the appearance of this muscle on the back is difficult to see and it rarely shows any real shape change on the back unless it is enlarged to un-safe sizes.
Supraspinalis Muscles --
Where -- Connecting to the top of the Scapula bone, sweeping down in a rough triangle to the Humerus beyond the shoulder joint. This is another Interior muscle that lays under the Trapezius muscle of the shoulder and neck.
This muscle comes in a pair one either side of the back connected to either Scapula and Humerus.
What -- This muscle is responsible for Abduction of the arm, and is a supporter muscle to the deltoid. However in relation to the core the Supraspinalis plays a role in countering the pulls of the core muscles on the shoulder and Scapula.
Appearance -- As an Interior muscle the Supraspinalis rarely if ever shows up in the shape of the back, especially due to the fact it is completely covered by the Trapezius.
Teres Major and Minor Muscles --
Where -- A pair of muscles on the Posterior aspect of the shoulder joint, these connect just beyond the shoulder joint as well as coming down and attaching to the Scapula.
These two muscles appear on both shoulder joints.
What -- These muscles assist in Adduction of the arm as well as Medial and Lateral rotation and do pull on the Scapula along with many other core muscles.
Appearance -- Interior muscle again and it tends not to appear on the back or shoulder.
Rhomboid Muscles --
Where -- Connecting to the Thoracic Vertebra it sweeps down in several small muscle groups to the medial aspect of the Scapula, a small group of slightly downward angled muscles. This is an Interior muscle that lays underneath the Trapezius muscle of the spine and shoulder.
This muscle comes in two groups, one group either side of the spine connecting across the back of the vertebrae under the Trapezius muscle, connecting to the Scapula on that side of the back.
What -- These muscles play a major role in Adduction and Medial rotation of the Scapula bone and it plays a role balancing the other muscles of the Scapula and providing counter pull for other muscles.
Appearance -- An Interior muscle that lays under the Trapezius, it rarely if ever appears on the back of the body.
Subscapularis Muscles --
Where -- This is a large triangular muscle found underneath the Scapula, a very deep muscle laying under the Scapula bone. This Muscles attaches to the Scapula along the Interior aspect and then flows up to the Humerus.
This muscle comes in a pair one underneath either Scapula bone on the Posterior aspect of the body.
What -- This plays a major role in Medial rotation of the arm, but also plays a role in holding and stabilizing the Scapula.
Appearance -- This Muscle does not appear on the back due to the covering muscles and bone structures.
Levator Scapulae --
Where -- This muscle connects to the Cervical Vertebrae near the top of the spin, it moves down and thickens finally connecting with the top of the Scapula, on the upper most edge of the Scapula Ridge.
This muscle comes in a pair one either side of the neck, connecting to the respective Scapula.
What -- This muscle is responsible for lifting both the shoulder and the Scapular, as well as pulling the neck back and to the side. It plays a role in countering the pull of the other muscles in the back and countering support of its twin on the other side of the neck.
Appearance -- This is another Interior muscle under the Trapezius and so plays a minor role in forming the appearance of the neck.
Where -- This is on the underside of the shoulder joint, connecting to both the lower edge of the Scapula and the Medial aspect of the Humerus, it is a very small muscle.
What -- This plays a role in Adduction of the arm as well as flexing of the shoulder joint, however it also places a minor pull on the Scapula.
Appearance -- This muscle does not appear commonly on the surface of the body, but may become visible on the inside of the shoulder joint.
Erector Spinae --
Where -- This is three groups of Interior muscles that begin at the Cervical Vertebrae sweep down the spine, connecting to the Ribs, Iliac Crest, and Lumbar Vertebrae.
These muscles come in identical groups either side of the back.
What -- These muscles help to extend the spine and also help to hold the body in its upright position, helping to counter the pull of the stomach and chest muscles, such as the Rectus Abdominis and the Pectorals.
Appearance -- Being Interior this muscle has little effect on the shape of the back.
Latissimus Dorsi --
Where -- This muscle connects to the Thoracic and Lumbar Vertebrae and connects all the way up to the Humerus. It is a massive triangular muscle that exists on the superficial aspect of the middle and lower back.
This muscle comes in a pair, one on either side of the back.
What -- This plays a role in supporting the back, it also plays a role in pulling the arm back or inwards, and can provide downward pull on the arms, as well as countering some of the pull of the abdominals.
Appearance -- This muscle provides much of the shape and appearance of the lower back.
Quadratus Lumborum --
Where -- This muscle connects from the Illiac Crest up to the base of the ribs.
This muscle comes in a pair one either side of the back.
What -- This muscle plays a major role in Lateral Flexion of the Lumbar Vertebrae, as well as playing a role in the movement of the diaphragm, and in supporting the core of the body in the complex interplay of muscular pulls.
Appearance -- this is a deep muscle and rarely if ever plays a role in the appearance of the back.
Psoas and Iliacus --
Where -- These muscle come across the hip joint, joining both the Lumbar Vertebrae and the Iliac Crest as well as moving down to join the Femur.
These Muscles appear on both sides of the lower back joining the respective thighs.
What -- These muscles mainly play roles in the movement of the back, but also play a minor role in supporting the lower back.
Appearance -- Both deep muscles, these play nearly no role in the appearance of the lower back.
Gluteus Maximus, Medius and Minimus --
Where -- These are a group of three muscles that lay over each other like layers of fabrics, each one joins to the Iliac Crest and femur, with most connecting to the Sacrum and Coccyx as well.
These muscles appear on both sides of the Glutial aspect of the body.
What -- While these muscles play a major role only in the actions of the legs, such as medial and lateral rotation and Abduction and Adduction they do play a minor role in stabilizing and supporting the Pelvis.
Appearance -- These are the muscles that give people a curved backside, and the main muscle for this is the Gluteus Maximus.
Anterior Aspect of the Core ((The Chest, The Stomach))
Pectoralis Major --
Where -- This muscle connects to the Sternum, Ribs, Clavicle and sweeps across the chest in a large triangle passing across the shoulder joint and connecting to the Humerus.
This muscle comes in a pair one either side of the chest, joining across the centre of the sternum.
What -- This muscle plays a role in Adduction and medially rotating the arm, as well as a lesser role in drawing the shoulders forward, and curving the upper portion of the spine. It plays a major role in counteracting the pull of the back muscles.
Appearance -- This plays a large role in the appearance of the chest, providing shape and tension to the chest, it also provides support to the flesh on the front of the chest, making it just as important for the appearance of the female chest.
Pectoralis Minor --
Where -- This is an interior muscle that lays under the Pectoralis Major, it connects to the ribs and passes right around the body to connect to the Scapula at the back.
This muscle comes in a pair on either side of the chest lying under the respective Pectoralis Major.
What -- This muscle plays a major role in the anterior movement of the shoulders, as well as the downward movement of the shoulders. It plays a major role in counteracting the pull of the back muscles on the shoulders and keeping the posture of the upper back.
Appearance -- As an Interior muscle this muscle rarely shows any sign on the outside appearance of the body, however many women find this muscle plays a greater role in their appearance as it helps tone and support the flesh on and around the chest.
Serratus Anterior --
Where -- These muscle groups join to the Ribs and wraps around the body joining to the Scapula, under the level of the Pectoralis muscles it covers the lower ribs primarily.
These muscle groups are mirrored on either side of the body.
What -- These draw the Scapula down and forwards, they play a major role in pushing and in curving the shoulders inwards.
Appearance -- these cover the lower ribs and when well trained can often cause a serrated effect over the lower ribs.
External Obliques --
Where -- This is a Superficial aspect muscle on the side of the stomach, it joins the Iliac Crest, the ribs and the Linea Alba ((Tendons on the stomachs midline)). It is a large roughly trapezoidal muscle that covers part of the lower ribs.
This muscle appears in a pair one either side of the stomach.
What -- This muscle plays a role in Rotation of the Trunk as well as Lateral Flexion of the truck. It also plays a role as part of the chain for raising the leg and supports and counters the pull of its twin muscle.
Appearance -- This muscle provides much of the shape to the side of the stomach, and plays a major role in giving definition to the sides of the stomach and top of the hips.
Internal Obliques --
Where -- This is a similar shape to the External oblique, however it joins the Ribs, Iliac Crest and Linea Alba in a different pattern, it also is slightly smaller and sits under the External Oblique.
This muscle appears in a pair one either side of the stomach.
What -- This muscle plays roles in Rotation of the Trunk, Lateral Flexion, it also plays a role in the chain for raising the leg, and supports and counters the pull of its twin muscle.
Appearance -- This muscle provides little of the shape of the stomach, but does support the External oblique physical giving it some thickness.
Rectus Abdominis --
Where -- This muscle covers the entire centre of the abdomen, connecting the Pubic bone, the Sternum and the Lower Ribs.
What -- This muscle plays a major role in flexing the Vertebral column, as well as supporting the posture and countering the pull of other muscles. It also plays a major role as a sheath around the abdomen holding organs in place.
Appearance -- This muscle gives people the classic six pack, with the lowest section of the muscle that connects to the Pubic bone is not often visible.
Transversus Abdominis --
Where -- This muscle lays under the Rectus Abdominis and the Internal Obliques. It is a large muscle connecting the Iliac crest, Rib Cage, Vertebrae, Pubic bone, Sternum and Linea Alba.
This muscle comes in a pair one either side of the body.
What -- This muscle plays a major role in the Lateral and Anterior flexion of the Vertebral column, bending the body both forwards and sideways. It also Supports the posture of the body, acts in the chain for raising and holding the legs, and counters the pull of many back and leg muscles.
Appearance -- Being one of the deepest muscles on the stomach it plays little role in the appearance of the stomach.
While these are the majority of the muscles referred to as the "core muscles" due to both their actions and positions on the body, it must be remembered that very few muscles work in isolation and all the muscles of the body, including those in the neck, legs and arms are all effected by working the core muscles.
Most notably the Hamstring tendon plays a major role in core flexibility and strength.
Theories of Developing the Core for Sport
The basic theory of developing the core safely with exercises like Calisthenics is to target general areas and groups of muscles in the core rather than Isolating and working individual muscles, this often means greater weight of time spent doing individual exercises compared with overloading the limb muscles.
Problems of Developing the Core for Sport.
The complexities of developing the core for anything, but most notably for the sport, lead to it being one of the most challenging parts of the body to be developed to athlete levels. However it is also one of the most highly used part of the body that means improper training can often result in problems even for people only taking part in light core training.
One of the key problems with developing the Core muscles is that as a muscles ability increases through exercise the tendons and connective tissue of the muscles often reduces in length and thickens, in normal training of the arms and leg muscles this can cause some serious problems, but in the core muscles this can result in even more serious problems including SPINAL condition such as Lordosis, Kyosis which are both muscular and tendon associated problems causing deformation of the spine similar in basic theory to Scoliosis.
Similar to flexibility problems instability problems come about when a antagonistic and agonistic group of muscles are imbalanced. In the limbs this is often challenging, but the antagonistic and agonistic groups are often quite small and basically very isolated... however in the core the agonistic antagonistic interactions are much more complex, and each muscle's strength pulling and tensioning against another. This complex pattern of muscles creates our posture, strength and mobility, but when lost can cause many problems including back pain, spine problems and posture problems.
Benefits of Developing the Core for Sport
The core is one of the main parts of the body and it is becoming more and more commonly accepted after the recent obsession with developing arms and legs, that the core is one of the key parts of the body to develop for any sport. The core not only creates movement and force in and around itself but it is also the only route for transmission of force from one part of the body to another.
Working the Core for Flexibility
Types of Stretches --
Static Stretching -- This is a basic type of stretching where a limb or muscle is moved into a stretched position and then held for 5-20seconds and relaxed. Performing tugging or bouncing at the end of the stretch can help develop flexibility more rapidly but risks tearing the tendon or muscle being stretched and is only recommended for experienced, skilled, and well trained (in flexibility) people.
Contract and Relax Stretching -- This is a variation on the static stretch and is based upon the tensioning of a tendon. Performing a basic static stretch and then contracting the stretched muscle often by pushing against the stretch application limb for a few seconds then repeating the static stretch. This kind of stretching has many benefits on permanently tensioned muscles such as the leg or core muscles, and can help the muscle relax to make stretching more effective.
Dynamic Stretching -- This is a form of stretching that takes the body through movements in a slow and controlled manner, often using support bars of harnesses to keep the movements controlled, it moves through a range of motion and then pushes and works the end of the range of motion to increase flexibility. However without great care taken to remain gentle and controlled in the movements injury is common.
This post has been edited by Attalim: Sun Jul 11, 2010 08:42 AM