Yoga: Why does it feel so good? Part 3 – Skeletal and muscular systems
Skeletal and muscular systems
The spine is fascinating in the way that it has evolved in order to maintain the upright stance of the body. It is curved the entire length and the primary curve is the shape the spine exhibits in the womb and after birth into adulthood, it changes so that we have secondary curves too. The primary curve is primarily in the thoracic spine but it also moves below the lumbar region into the sacrum.
When we experience spinal flexion, the spine is increasing in length in the primary curves and decreasing in the secondary for example, during the cat asana. For spinal extension, there is an increase in length in the secondary curves and a decrease in the primary for example, during the cow asana.
When our spine changes shape and length, our breathing adapts accordingly. When we flex our spine, our body naturally inhales and naturally it exhales on extension. Due to these curves, and the closely knit nature of the vertebrae of the spine and separated by cartilaginous discs, held together with ligaments, there are some limitations on the range of movement. For the spine to twist and bend laterally, the hips must be unrestricted to allow that movement to be mirrored in the lumbar spine. During axial extension, all curves are reduced at once which goes against the natural movement of the spine. Axial extension can only be accomplished consciously. In axial extension, the breath volume lowers but the length of breath increases. By combining the three bhandas with axial spinal extension, we are merging the asana practice with pranayama – the ultimate accomplishment. The asana which demonstrates this most obviously is mahamudra.
The spine has an intrinsic equilibrium which means that if all other muscles were taken away from the spine, it would still remain upright. Spinal movement produces energy which causes it to return to its neutral position.
Yoga helps release the stored potential energy of the axial skeleton by identifying and releasing the less efficient muscle effort which gets in the way of the elements of the skeleton (pelvis and rib cage) which work intrinsically. By allowing these elements to work independently as they should, we stop over exerting ourselves by using less muscles to perform the same task.
The skeleton forms part of all other systems – bones secrete hormones (endocrine) which affects metabolism, the marrow produces red blood cells and calcium assists the work of the neurons which are part of the nervous system. Where one bone meets another, you will find a joint. In yoga, we are primarily concerned with the synovial joints. These are composed of bones articulating with each other that have synovial fluid in between. They have the biggest range of motion.
The body never moves only one joint nor does it only perform one joint action. As a result, success in an asana should be measured by how much balance or intrinsic equilibrium there is through the whole body rather than being measured by the range of motion in a single joint. The job of the skeletal system is to transfer weight and force by way of the ligaments, through bones, in any way the joints allow. The muscles move the bones into place, as directed by the nervous system, to enable this to happen. Muscles create movement, joints enable movement and connective tissue translates movement from tissue to tissue. Bones absorb and transmit movement and nerves do the organizing and co-ordination.
– muscles don’t work as discrete units, they work together
– different muscles can create different movements for different people
– a muscle doesn’t always function better simply because it’s toned.
– there isn’t always a correct set of muscles for executing a moment.
We have muscles which work without conscious direction, powered by the autonomic nervous system – the heart for example, and those which we consciously move. The diaphragm works both autonomically and consciously and is linked to over 100 joints in the body.
Muscle tone is important because if a muscle or group of muscles is too low, when a muscle is needed to participate in a task, it might not be readily available and other muscles must compensate. This leads to injury. Nerve endings in the muscles help calibrate their tone to a sophisticated degree. Yoga however, helps to ensure that the right muscles are toned to the right level to optimise movement in the body and ensure that the stress of movement is distributed effectively, helping to prevent injury. In the majority of situations, flexibility is not determined by the actual physical length of the muscle or the muscle fibres that compose it by set by the proprioceptive nerve endings in the muscle. This setting is established in the nervous system through previous experiences regarding what is appropriate, safe and functional. Additionally, by working the muscles, we are improving blood flow around the body.
Increasing flexibility and strength is as much about re-educating the nervous system through conscious attention and practice as it is about stretching and repetitions. An asana is a container for an experience. It is not an exercise for strengthening a particular muscle or muscle group.
The whole experience of asana practice is greater than the sum of its parts. How we move into and through an asana depends on our starting condition e.g. someone with very open shoulders might need to internally rotate the humerus relative to the scapula in adho mukha svanasana. A person with the opposite may be doing all they can to open their shoulders. Both actions could be functional because the point is not to do it ‘right’ but to find the relationship between all the parts of the body that will let the experience of the asana resonate through the whole body – cells, tissues, fluids and systems.