Swimming Anatomy полностью

The elbow divides the arm into an upper and lower component. The elbow is a hinge joint restricted to two movements, extension and flexion. Elbow extension occurs when you straighten your arm, moving the forearm away from the upper arm. Elbow flexion is the opposite, involving bending the forearm toward the upper arm. The structural framework of the upper arm is the humerus. The lower arm, typically called the forearm (figure 2.1, a-b), is supported by the radius and ulna. These three bones are the major attachment sites and levers upon which the muscles of the arm and forearm originate and act on. The two primary muscle groups in the arms that are the target of the strengthening exercises in this chapter are the elbow extensors and elbow flexors. Both contribute to the maintenance of proper arm position and propulsion during each of the four competitive strokes.

Figure 2.1 Forearm: (a)front and (b)back.

The primary elbow extensor is the triceps brachii (figure 2.2). Tricepsrefers to its three heads of proximal attachment, and brachii refers to its origination in the arm. The medial and lateral heads arise from attachment sites on the humerus, and the long head crosses the shoulder joint and arises from the scapula (shoulder blade). The three heads unite to form the tendon that crosses behind the elbow joint and inserts onto the olecranon process of the ulna. The olecranon process forms the tip of the elbow when it is bent to 90 degrees. A much smaller triangular muscle called the anconeus assists the triceps in extending the elbow joint and is important as an elbow stabilizer. The anconeus is intimate with the lateral head of the triceps brachii; sometimes the fibers of the two muscles blend into one another.

The primary elbow flexors are the biceps brachii and the brachialis (figure 2.3). As the name implies, the biceps has two heads, a long and a short, both of which cross the shoulder joint and attach to the scapula. The two heads fuse to form a common tendon that crosses the front of the elbow joint to attach to the radius approximately 1.5 inches (4 cm) past the elbow. Besides being an elbow flexor, the biceps brachii contributes to the forearm movement of supination, which is the position when the palm is facing up. Your hands would be in this position to carry a bowl of soup. The brachialis lies beneath the biceps brachii and arises at the midpoint of the humerus. It attaches to the ulna just after it passes anteriorly to (in front of) the elbow joint. A smaller muscle that at times contributes to elbow flexion is the brachioradialis. This muscle arises from the lateral aspect of the humerus just above the elbow and travels along the outer part of the forearm to attach to the radius just above the wrist joint.

Despite difference in stroke mechanics, freestyle, butterfly, and backstroke have similar activation patterns of the elbow flexors and extensors during the pull phase. As the swimmer progresses through the catch, the elbow moves from full extension to a position of 30 to 90 degrees of elbow flexion at midpull, depending on the stroke and the swimmer’s mechanics. The primary muscles responsible for generating the change in elbow position and, when necessary, maintaining the elbow in a fixed position of flexion are the biceps brachii and brachialis. After the elbow reaches a point of maximal flexion during the midpull, it progresses into an extended position during the remainder of the pull phase. This action aids in generating propulsive forces and is brought about primarily by active recruitment of the triceps brachii. The degree of the propulsive force generated depends on the point in the pull phase at which the swimmer removes the hand from the water to initiate the recovery phase. In freestyle and butterfly many coaches are now teaching their swimmers to begin the recovery process as the hand reaches the hip, before the elbow is fully extended. Meanwhile, backstroke mechanics involve the catch phase, terminating with full extension of the elbow joint.

Figure 2.2 Triceps brachii.

Figure 2.3 Biceps brachii, brachialis, and brachioradialis.

Unlike in the other strokes, during the initial portion of the pull phase of the breaststroke the triceps brachii is the primary muscle that is active at the elbow joint, functioning to maintain the elbow in a position near full extension. As the hands begin to turn inward marking the transition from the outsweep to the insweep, the muscle activation patterns at the elbow begin to change. The elbow flexors (biceps brachii and brachialis) activate to bring the elbow into a flexed position, a movement that aids in the generation of propulsive force. As the swimmer transitions into the recovery phase, the recruitment pattern changes again. The triceps brachii becomes activated to extend the elbow joint, thereby straightening the arm and preparing the swimmer to begin the next pull phase.