Kaminoff’s Yoga Anatomy discusses anatomical concepts as they apply to asana practice. The first five chapters discuss the mechanism and action of breath, spinal structure and movements, joint actions across the skeletal system, some basic properties of muscles and their interactions, and the general approach used during the individual asana discussions later in the book. In this essay, I will summarize and comment on those aspects of the first five chapters that I have found most important for my personal and teaching asana practice.
Chapter One describes the process of breathing. The authors note that the relationship between the thoracic and abdominal cavities, separated and shaped by the diaphragm, a parachute shaped muscle that can push down to expand the lungs and, via pressure gradient, move fresh air from outside into the lungs. There are two main actions that can be affected by diaphragm contraction: bulging of the belly, and expansion of the lower ribs. I was most interested in the connections drawn between the spine, posture, and breathing. Because breathing is ultimately the result of expansion of the thoracic cavity, it is fundamentally impacted by the shape of the spine and ribs which encapsulate it. Spinal extension eases inhalation, whereas spinal flexion eases exhalation. Related to this idea, posture dramatically impacts the depth and quality of our breath. The chapter continues to discuss the accessory muscles which can impact breathing, although these are less effective than the diaphragm. I would be interested to examine yoga poses which require stretching or contracting these accessory muscles, and examining the effects on the breath. This chapter allowed me to draw a connection between active breathing and the muscular action that enables a certain pose, as well as the connection between spinal integrity and breath. When yoga teachers cue to sync breath with poses, from now on, I will think about the shape and angles of my thoracic and abdominal cavities, the expansion or contraction in my lower ribs, and the shape of my spine.
Chapter Two explains the origin, function, and articulation of the spine. The authors begin by giving an extremely brief discussion of evolutionary history, with the conclusion that the human spinal curves developed for their specific functions: the thoracic curve for an arching support, since arches are more stable than straight lines; the cervical curve, which gives us greater mobility in the head, which contains the primary senses; and the lumbar curve, which allows us to stand upright and use our upper limbs for a variety of tasks. This evolutionary history is paralleled by early childhood development of the spine. The spine is constructed of 24 vertebrae, intermediate cartilage discs, and intertwining ligaments, which combine to give us a combination of supportive structure and flexibility. There are five types of spinal movement: flexion, extension, axial rotation (twisting), lateral flexion (side bending), and the somewhat less common axial extension. The chapter goes on to describe the difference between each of these actions and simply changing position in space. I will take great care to watch and address this concern in my teaching practice.
Chapter Three describes the skeletal system, and in particular, the joint actions at play during asana practice. Synovial joints are the most mobile, and contain a capsule filled with synovial fluid separating and lubricating a small space between two bones, each coated at their articulating surface with a cushy hyaline cartilage. The bulk of the chapter contains a list of joint actions in a specific set of limbs. The main takeaway that I got from this chapter was that a single joint action cannot be isolated from the entire movement of the body, and that the whole body must be studied in its entirety, rather than focusing on a single joint action.
Chapter Four is concerned with the muscular system. There are three basic muscle types: skeletal, smooth, and cardiac. Skeletal muscles are the most relevant to yoga since they are able to be consciously controlled. Muscles may contract in one of three ways: concentric, eccentric, or isometric contraction. Concentric contraction is a shortening of the muscle, eccentric contraction is a lengthening of the muscle, and isometric contraction occurs when the muscle is actively working, but doesn’t actively move the body in any way. Each muscle has a pairing muscle; these are called agonist-antagonist pairs. For example, the bicep and the tricep are such a pair. As the bicep undergoes concentric contraction, the tricep necessarily undergoes eccentric contraction, and vice versa. In the case of pulling an object up towards you, the bicep would be the primary mover, and as such, is considered the agonist for that action. Reciprocal inhibition is a process wherein when one muscle contracts, its antagonist pair receives neural signals prompting it not to exhibit the same type of contraction. We can take advantage of this in yoga to deepen relaxation of certain muscles in stretching exercises. There can also be synergistic action wherein different muscles move in conjunction to create a specific action. Several principles of skeletal muscles are laid out in this chapter. The one I found most interesting was the distinction between tone and sensitivity. In this case, tone means the readiness to respond to a stimulus, whereas sensitivity means the likelihood that a stimulus will be perceived.