Essentials: Anatomy & Physiology

Every load carried, pulled, or pushed with the hands transmits its weight to the axial skeleton and then the ground through the shoulder skeleton and musculature. You can’t pull a weight off the ground without shoulder muscle contribution. You can’t push overhead without significant shoulder contribution. Even something as simple as holding a bag of groceries recruits the muscles of the shoulder.

The musculature of the shoulder joints is structured and oriented in a manner to provide mobility in every direction around the ball-and-socket joint. It also provides stability, given the relative lack of bony support in the joint.

There are three layers of posterior vertebral muscles overlaying the vertebral column, and each layer affects vertebral position in postural stability and movement. The anterior musculature is also organized in an approximation of a three-layer structure. When considering gross movement of the vertebral column, vis-à-vis arching and rounding, we often only think of the erector spinae as driving arching and the rectus abdominis as driving rounding. However, movement into those positions is complex and requires more than the action of the prime movers.

Many muscles act upon the lumbar vertebrae during anterior flexion, rotation, and lateral flexion. What we commonly refer to as abdominal muscles carry a major role in lumbar movement. Some of these muscles attach to and act directly upon the lumbar vertebrae. Others that are not attached to the vertebrae act indirectly through moving bones that are.

As with musculature in other segments of the vertebral column, the lumbar muscles have attachments in the segments above and below. These muscles contribute to respiration, posture, and the mobility of the vertebral column.

Many muscles in the thoracic segment contribute to respiratory function by moving the costals. Examples of this are the external and internal intercostals, which are found circumferentially around the thoracic cavity — posterior, lateral, and anterior. The transversus thoracis and diaphragm also contribute to respiration.

The thoracic segment of the body is home to the thoracic vertebrae, the ribs (costals), and numerous muscles that move the vertebral column, ribs, and structures attached to the thoracic skeleton. Deep muscles that arise and act primarily within the thoracic generally have contractile functions in respiration (breathing) and maintaining vertebral column posture.

The cervical vertebral skeleton serves as an attachment point for a large number of muscles, creating a complex set of moving connections between the skull, vertebrae, scapulae, clavicles, sternum, and ribs.

The cervical vertebral skeleton serves as an attachment for a large number of muscles that create a complex set of moving connections between the skull, vertebrae, scapulae, clavicles, sternum, and ribs.

Atrophy is a simple and opposing process to hypertrophy. Just as exercise can drive an adaptive increase in muscle mass, lack of exercise can cause a reductive adaptation or loss of muscle mass. As one would expect, the entire muscle may shrink in size such that it is easily and visually detectable, but atrophy occurs at every level of muscular organization, beginning with the molecular.

The physiological process of increasing the size of an entire muscle is known as hypertrophy. Human muscle has a huge capacity for hypertrophy and is able to increase in size by 200% or more. A person maintains this ability throughout his or her lifespan.

When muscles contract, the brain or a reflex mediated by the autonomic nervous system sends a signal out along a motor neuron (a nerve feeding information to a muscle). The neural signal hits the muscle cell, which triggers chemical events inside the cell. Those chemical events yield a binding of contractile proteins — actin to myosin — energy gets expended, myosin changes shape, causing sarcomere and cell shortening, and thus results in a production of force. No fewer than 20 muscle proteins and multiple other biochemicals are involved.

We often think of muscles only in the context of biceps, triceps, pecs, and quads, but to do so ignores the fact that there is more than one type of muscle cell in the human body. There are, in fact, three types of muscle cells: skeletal, cardiac, and smooth muscle cells. Skeletal muscle cells drive movement, cardiac muscle cells circulate blood, and smooth muscle cells move things like blood and waste through the vascular system and intestines.

Scoliosis involves the presence of abnormal curvatures along the vertebral column. The degree of scoliosis may vary dramatically from mild imperceptible curves to severe and physically perceptible deformations that limit movement capacity. Physicians diagnose any lateral deviation greater than 10 degrees from vertical as scoliosis. In the gym, it manifests as a hip or shoulder tilt when athletes should be maintaining a neutral position, level and parallel to the floor.

Osteoporosis is a disease in which loss of bone mineral content leads to a weakening of the microarchitecture of bone, making it susceptible to fracture from external forces. Think of it as porous bones (osteo = bone, porosis = more porous). Normal bone is much like limestone, a substance strong enough to serve as building material for huge structures. Conversely, diseased, extremely osteoporotic bone is much like blackboard chalk and easy to break.

The ankle joint (talocrural joint) is formed by the articulation of the tibia and fibula with the talus bone, one of the tarsals of the foot. During standing and ambulation, the weight of the body is borne by the tibia and transferred through the foot. The distal ends of the tibia and fibula, where they articulate with the talus, are the hard bumps we usually point to as the ankle bones. They form the widest point of the ankle joint. The talus sits in a groove formed underneath and within this structure.

The shoulder joints and their attachments to the axial skeleton are often referred to as the “shoulder girdle.” It is also common to refer to the whole structure as the “shoulder joint,” but it is important to note that the shoulder is not just a single joint. It is formed of two direct articulations and one indirect articulation. The anatomically correct names of these three joints are the glenohumeral, acromioclavicular, and sternoclavicular joints. Together, structurally and functionally, they form the freely moving joint system we call the shoulder.

Effective coaching requires efficient communication. This communication is greatly aided by coach and athlete sharing a terminology for both human movement and body parts. We’ve developed an exceedingly simple lesson in anatomy and physiology that we believe has improved our ability to accurately and precisely motivate desired behaviors and enhanced our athletes’ understanding of both movement and posture.

The vertebral column has two types of curves: kyphotic (an anterior arch) and lordotic (a posterior arch). A degree of kyphosis and lordosis is necessary to provide ergonomic support for the internal viscera and the body as a whole. Too much rounding (rolling the shoulders forward) or too much arching (pulling the shoulders back and pushing the gut forward) makes the vertebral column behave much like a shock absorber and dampens force transfer.

The sacrum sits below the lumbar vertebrae in the stack of bones we call the vertebral column (or spine in an anatomically incorrect nomenclature). When viewed from the back, it presents as a roughly triangular-shaped bone with four sets of foramen (the sacral foramen), which are aligned roughly vertically. Just inferior to the sacrum is the coccyx or tailbone. This fusion of four or five vertebrae is the termination of the axial skeleton.