The Anatomy and Kinetics of the body in relation to sporting application
The Anatomy and Kinetics of the body in relation to sporting application
Introduction
I am going to be analysing the bench press action from a anatomical standpoint looking at the structure and function of the wrist, elbow and shoulder. As well as the surrounding bone/connective tissue, ligaments, tendons, muscle type and structure and neural input in relation to the movement the joint permits when performing a bench press (see appendix 1)
The main articulations involved when performing a bench press are the shoulder, elbow and wrist. The shoulder or pectoral girdle consists of articulations between the clavicle, scapula and the proximal end of the humerus. Movements at this joint are largely passive in that the occur as a result of active movements of the scapula. The glenohumeral articulation (shoulder joint) has the greatest range of motion of any joint in the body. The scapula is suspended on the thoracic wall by muscle forming a functional joint called the scapulothoracic joint. These muscles act to stabilize and to actively move the scapula. Active movements of the scapula help increase the range of motion of the shoulder joint. Articular cartilage cushions this joint by covering the head of the humerus and face of the glenoid. Stabilizing the joint is the labrum, a ring of fibrous cartilage surrounding the glenoid.
The acromion (highest point of the shoulder) is formed by the outer end of the scapula extending over the shoulder joint. This is also called the acromial process. The acromioclavicular joint is the joint between the acromion of the scapula and the clavicle.
The shoulder bones are connected by ligaments and the bones are connected to the surrounding muscles by tendons.
Two major tendons of the shoulder are the biceps tendon, which attaches the biceps muscle to the shoulder, and the supraspinatus tendon, which helps form the rotator cuff. Accessory nerve initiates the trapezius muscle, Dorsal Scapular nerve initiates the rhomboideus muscles, Long thoracic nerve initiates the serratus anterior muscle and the major nerve for this action is the axillary nerve which initiates the deltoid and teres minor muscles. (see appendix 2)
The elbow joint is formed by the articulation of the humerus (upper arm bone) with the radius and ulna (the two bones of the forearm). (The radius is located on the thumb side of the forearm, the ulna on the little finger side.) The elbow is a hinge-like joint, capable of two movements: flexion (bending) and extension (straightening).
Movements of the elbow (flexion/extension) and forearm (pronation/supination) are carried out by different muscle groups. Flexion of the elbow is produced by three muscles: biceps brachii, brachialis, and brachioradialis. In addition to elbow flexion, the biceps brachii supinates ...
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The elbow joint is formed by the articulation of the humerus (upper arm bone) with the radius and ulna (the two bones of the forearm). (The radius is located on the thumb side of the forearm, the ulna on the little finger side.) The elbow is a hinge-like joint, capable of two movements: flexion (bending) and extension (straightening).
Movements of the elbow (flexion/extension) and forearm (pronation/supination) are carried out by different muscle groups. Flexion of the elbow is produced by three muscles: biceps brachii, brachialis, and brachioradialis. In addition to elbow flexion, the biceps brachii supinates the forearm (with the help of another muscle, called supinator). Extension of the elbow is produced by two muscles: triceps brachii and anconeus. Pronation of the forearm is carried out by two muscles: pronator quadratus and pronator teres. The disc-shaped upper end of the radius is called the head. The radial head articulates with the humerus, and also with the coronoid process of the ulna. The elbow joint is bound together by several ligaments. The ulnar collateral ligament stabilizes the medial side of the joint; the radial collateral ligament stabilizes the lateral side of the joint. The annular ligament encircles the head of the radius, binding it to the ulna. The three major nerves of the upper arm (the radial, ulnar, and median nerves) pass through the elbow region on their way to the hand. The ulnar nerve passes behind the medial epicondyle, close to the surface. (See appendix 3).
The wrist joint is a very complex type of joint between the distal end of the radius, a fibrocartilaginous disc at the distal end of the ulna, the carpal bones and the metacarpal bones. These complex articulations form an synovial joint at which the movements of flexion, extension, abduction and adduction. The forearm connects the elbow with the wrist an can also be divided into two compartments: an anterior and a posterior. Muscles in the anterior compartment pronate the radioulnar joints, flex the wrist and also flex the digits. Muscles in the posterior compartment help supinate the radioulnar joints, extend the wrist and help extend the digits. Flexion of the wrist is obtained primarily through the flexor carpi radialis and flexor carpi ulnaris and secondarily by the palmaris longus and long abductor of the thumb. Where as extension of the wrist is performed primarily by the extensor carpi radialis longus and brevis and by the extensor carpi ulnaris. The extenders of the fingers assist in extension when gripping the bar to perform the bench press. Supination is performed in the forearm by the supinator muscle, extensor carpi radialis longus and the biceps brachii of the upper arm. Pronation is performed by combined action of the pronator teres, pronator quadratus, and the flexor carpi radialis, and in extremely forceful pronation of the palmarus longus. Ulnar abduction (movement towards the fifth finger) is obtained by the combined actions of the extensor carpi ulnaris and flexor carpi ulnaris. Radial abduction (movement towards the thumb side) is obtained primarily by the long abductor and short extensor of the thumb, and secondarily by the extensor carpi radialis longus and brevis, flexor carpi radialis and the long extensor of the thumb (see appendix 4) . The Volar Radiocarpal Ligament is a broad membranous band, attached above to the anterior margin of the lower end of the radius and to the front of the lower end of the ulna; its fibres pass downward and medialward to be inserted into the volar surfaces of the navicular, lunate, and triangular bones, some being continued to the capitate. The dorsal radiocarpal ligament less thick and strong than the volar, is attached to the posterior border of the lower end of the radius; its fibres are directed downward and medialward, and are fixed to the dorsal surfaces of the navicular, lunate, and triangular. The ulnar collateral ligament is a rounded cord, attached above to the end of the styloid process of the ulna. The radial collateral ligament extends from the tip of the styloid process of the radius to the radial side of the navicular. Also the synovial membrane lines the deep surfaces of the ligaments, extending from the margin of the lower end of the radius and articular disk to the margins of the articular surfaces of the carpal bones. The wrist-joint is covered anteriorly by the flexor tendons and posteriorly by the extensor tendons. In all there are eight bones making up the formation of the wrist: Scaphoid, Lunate, Triquetrum, Trapezoid, Trapezium, Capitate, Hamate and Pisiform. The bench press is executed while lying flat on the back. The agonists (prime movers) in the bench are the triceps, deltoids, pectoralis major and minor, and the latissimus dorsai. Performed properly, the bench can produce incredible muscular hypertrophy of the pressing muscles. The most active portion of the triceps is the long head, which is even more active with a narrow grip. This is true even when overhead pressing, assuming the elbows are fully adducted. This is secondary to the greater widening of elbow flexion, in which the triceps brachii functions as the agonist. The anterior deltoid will be more active the more the trunk is inclined, as well as being more active with a wider grip. This is due to the fact that the anterior deltoid is just a flexor of the humerus, but also an adductor of it. The latissimus dorsai is highly active at the initiation of the concentric phase, with greater contraction the closer the elbows are to the torso, due to the degree of adduction required. The latissimus dorsai is an extensor as well as being a humeral adductor.
As previously mentioned, there are three phases involved when performing the bench press, the static phase, the concentric phase and the eccentric phase (see appendix 1).
During the concentric contraction, the working muscle shortens, pulling the bones on either side of the joint being used closer together. At the start of this concentric contraction, only a small number of motor units are activated, generating minimal force. As more force is required, additional motor units are called upon. If the weight being lifted is relatively light, many motor units will remain inactive; only a fraction of the total muscle contracts. However, if the weight is heavy, the muscle is fatigued or both, the muscle must recruit as many motor units and fibres as possible to accommodate the demands being placed on it. The amount of force that a muscle is able to generate increases with the number of motor units that are used or called upon. Whether or not you pause at the end of the concentric half of the rep, eventually you have to return the weight to the start position. This is called the eccentric phase. During the eccentric phase, nerve impulses continue to signal motor units to fire, even though fewer motor units are being used than during the concentric contraction. As a result, more stress is placed on each of the activated muscle fibres.
Combining the concentric and eccentric phases of the action produces an exercise's range of motion. Exercising through a full range of motion is safe as long as the action is slow and under control.
The elbow, wrist and shoulder joints play major roles in all three of these phases as they permit the movement allowed to perform the action of a bench press. All these joints have similar and different anatomical structures, For example there all synovial joints and are all needed immensely by the body to carry out different movements, and in this case, the bench press. They are also very different in the fact that they all are different types of joint, the wrist is a condyloid joint, the shoulder is a ball and socket joint and the elbow is a hinge joint. Each type of articulation allows very different types of movement due to the surrounding factors involved which either help enhance the range of movement or restrict it.