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The linea alba is a white, fibrous band that is made of the bilateral rectus sheaths that join at the anterior midline of the body. These enclose the rectus abdominis muscles (a pair of long, linear muscles, commonly called the “sit-up” muscles) that originate at the pubic crest and symphysis, and extend the length of the body’s trunk. Each muscle is segmented by three transverse bands of collagen fibers called the tendinous intersections . This results in the look of “six-pack abs,” as each segment hypertrophies on individuals at the gym who do many sit-ups.
The posterior abdominal wall is formed by the lumbar vertebrae, parts of the ilia of the hip bones, psoas major and iliacus muscles, and quadratus lumborum muscle. This part of the core plays a key role in stabilizing the rest of the body and maintaining posture.
If you injured your shoulder while you were kayaking, the first thing a physical therapist would do during your first visit is to assess the functionality of the joint. The range of motion of a particular joint refers to the normal movements the joint performs. The PT will ask you to abduct and adduct, circumduct, and flex and extend the arm. The PT will note the shoulder’s degree of function, and based on the assessment of the injury, will create an appropriate physical therapy plan.
The first step in physical therapy will probably be applying a heat pack to the injured site, which acts much like a warm-up to draw blood to the area, to enhance healing. You will be instructed to do a series of exercises to continue the therapy at home, followed by icing, to decrease inflammation and swelling, which will continue for several weeks. When physical therapy is complete, the PT will do an exit exam and send a detailed report on the improved range of motion and return of normal limb function to your doctor. Gradually, as the injury heals, the shoulder will begin to function correctly. A PT works closely with patients to help them get back to their normal level of physical activity.
The muscles of the chest serve to facilitate breathing by changing the size of the thoracic cavity ( [link] ). When you inhale, your chest rises because the cavity expands. Alternately, when you exhale, your chest falls because the thoracic cavity decreases in size.
| Muscles of the Thorax | |||||
|---|---|---|---|---|---|
| Movement | Target | Target motion direction | Prime mover | Origin | Insertion |
| Inhalation; exhalation | Thoracic cavity | Compression; expansion | Diaphragm | Sternum; ribs 6–12; lumbar vertebrae | Central tendon |
| Inhalation;exhalation | Ribs | Elevation (expands thoracic cavity) | External intercostals | Rib superior to each intercostal muscle | Rib inferior to each intercostal muscle |
| Forced exhalation | Ribs | Movement along superior/inferior axis to bring ribs closer together | Internal intercostals | Rib inferior to each intercostal muscle | Rib superior to each intercostal muscle |
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