As human body and performance instructors, it is important to understand not only the parts of the body, but how those parts function together to work as a whole. Functional anatomy is defined as “anatomy studied in its relation to function”. In lay terms, this often gets used amongst human performance and therapy experts to talk about how the body moves and is shaped. This includes the fields of kinesiology (study of mechanics of body movement) and biomechanics (the study of the mechanical laws relating to the movement or structure of living organisms). All of these terms overlap and some will claim they are very distinct while others will adamantly refute that.
For our purposes, we will use the definition of “the study of the systems that affect the visible body in motion and rest.” Though the human body is fully integrated and the argument can be made that every system affects the visible body in motion and rest, we will focus in a bit on the more prominent systems that affect movement and posture. The classical systems that are taught in anatomy classes that comprise the components of movement are the muscular and skeletal systems.
Most every book on body movement that you see will focus on the names and locations of bones in the skeletal system and the names, locations, attachment points, and theoretical actions of muscles in the muscular system. Focusing on these two systems is at best incomplete and at worst egregious. Recent anatomical research in the last twenty years has focused on two very important systems that pertain directly to functional anatomy – the nervous system and the fascial system.
The nervous system is the obvious next system that directly innervates (controls) the contractions of skeletal muscles, causing tension to be created through shortening of the muscle fibers (cells). However, the incorrect assumption is that this tension is solely focused on the ends of the muscles where they attach to the bones via tendons or direct muscle fiber insertion. It also does not take into account the other half of the function of the nervous system in body movement, which is picking up sensory inputs like touch and proprioception (balance and position in space) that is processed to influence and control the motor output (muscle contraction).
So let’s talk about the four major systems and also connections involved in controlling movement and posture of the body:
Compression rods serve as solid objects to which tension can be anchored in multiple directions.
The skeletal system is typically viewed through the lens of levers moving around a pivot point (articulation) that get manipulated by a force (skeletal muscle). Though this is not completely wrong, it does not take into account the various different vectors (directions) of forces at work throughout the body. A better model would be to consider the skeleton as the compression rods or rigid parts of a tensegrity model. This is a model in which you see self-contained areas of tension (muscles, fascia, other connective tissue) pulling on areas of compression (bones). With this perspective, you can appreciate all of the forces at work. The compression rods now serve as anchor points for tension to be developed between multiple regions.
A tensegrity model also helps us to better understand why bones end up with the shapes they have. Lumps, bumps, grooves, ridges, holes, and lines on bones are all created by tension forces through tendons and ligaments pulling on them during development as well as spaces left open for communication systems (e.g. nerves, arteries, and veins) to pass through. This model also helps us to explain why forces generated in far off places in the body can have an affect in a seemingly unrelated place.
The classical view of the muscular system again involves the overly simplistic view of muscle cells generating tension by contracting and pulling on tendons, which in turn pull on bones. The challenge with this model is that it limits us to the knowledge that each individual muscle cell is wrapped in connective tissue fibers, which in turn are bundled and wrapped in fibers, which are subsequently all wrapped together in another set of fibers. We now know that forces generated by muscle tension are also distributed across another layer of connective tissue called fascia that completely engulfs entire muscles. Fascia is then arranged in patterns like rivers throughout the body that are pinned down at specific parts of bones, but also distribute force more evenly across the entire pattern, often from one end of the body to another.
Another shortcoming of the traditional study of the muscular system is the theoretical actions that the muscles perform at joints. For instance, we learn that the prime mover (main muscle) of elbow flexion is the brachialis muscle and that the biceps brachii acts as a synergist (helps) and the triceps brachii acts as the antagonist (works against). Newer studies reveal that in order to produce elbow flexion, we have to take in to consideration many points of stabilization and distribution of forces to allow the arm to stand still while the forearm moves around the elbow to produce that flexion. Functionally, this means that some fraction of many muscles are coordinating contractions (controlled by the nervous system), while applying those stabilizing forces through fascial rivers, in order to create the tension and resistance to allow compressive circular movement around the elbow joint.
Muscle and Deep Fascia
We now know this picture is very incomplete when it comes to the connective tissue and fascia between muscles and bones.
The yellow neurons are vital part of our understanding of functional anatomy.
One of three major communication systems in the body, the nervous system follows a model of input, processing and output to govern all of our actions. Our input, or sensory nervous system, is comprised various types of neurons (individual cells) that pick up information from both the world around us (exteroceptors) and the environment inside our bodies (interoceptors). We actually use different neurons for the sensations of light touch, deep touch, pressure, pain, and temperature. Another type of sensory input that is prominent in our discussion of functional anatomy is proprioception. Proprioception is our sense of body positioning. Like a GPS system, proprioceptors lets our brain know where various body parts are in relation to each other. For instance, if you close your eyes and hold your hands far out to the side without touching anything, you brain will know that your hand is far away.
Though this sounds ridiculously simple, it is a very important sensation for coordination of movement. Proprioceptors are concentrated in key areas in the body, such as surrounding our movable joints between bones (synovial joints) and areas key to spatial orientation and balance such as our ankles (standing upright) and base of our skull in the neck (position of head, especially eyes). These proprioceptive inputs are sent to the central nervous system (brain and spinal cord) hundreds of times a second from millions of different locations for processing. Our central nervous system then does an amazing job of very quickly processing this information and coordinating muscle contractions to create balance in various body positions (walking, standing, moving, etc.).
We are born with the coordination of some movements, but others develop after birth. Some develop early in life while others, like athletic or musical motor skills, may take years of conscious practice to refine. Regardless, coordinated movements take practice and time. If these connections and memorized coordinated patterns are disrupted or damaged, they have to be retrained, sometimes as if a baby learning to walk again. Body movement practitioners (yoga instructors, martial arts instructors, personal trainers, athletic trainers, etc.) inherently see these movement patterns develop over time and at different rates in their clients and students.
Gaining prominence in only the last twenty years or so, the fascia (organized connective tissue) between the various layers of skin, muscle, bones, and other organs turns out to be one of the most vital components of communication, coordination, and control in the body. It is our entire structure. It is the framework that not only creates the shapes of organs and holds them all together, it also helps various parts of the body communicate with each other much like the vibrations in a spider web alerting the distant spider to its prey. This tugging and pulling on long stringy protein fibers such as collagen are then translated to signals to the inside of the cells, which then affect genetic expression and enzyme activity.
More careful dissections with regard to the connective tissue has led to the discovery of organized fascial sheets or anatomy trains (as coined by Thomas Myers). Though a relatively new concept and much argument to be had over definitions and boundaries, the framework of looking at muscles, bones, and joints as overlapping organized sets of tensegrity structures creates a much better paradigm for studying movement in the human body.
The “stuff” we used to cut away to get to the interesting organs turns out to be the most important parts of the body.