There are more than 640 muscles in our body and these make up more than half of our total weight. We can categorise our muscles as either voluntary or involuntary. As the name suggests we have very little power over the involuntary muscles, therefore it is the voluntary muscles which a yoga practice mostly addresses. The voluntary muscles are called skeletal muscles because without them the skeleton would neither be able to move or stand upright. These muscles effect movement and posture.
Postural muscles are important because they keep your body upright while standing or sitting. Strong and flexible postural muscles are energy efficient for the body and they make less strain on the joints and ligaments. With the support of the postural muscles the joints are less likely to degenerate and contract painful conditions like arthritis. Yoga poses firstly address correct alignment of our joints and then by holding this alignment for a length of time we build up strength in the postural muscles.
At the end of each of our skeletal muscles are tendons which attach to our bones. Therefore to create a movement we simply need to contract (shorten) the muscle that attaches to the particular bone that we want to move. Ideally muscles need to be strong and flexible to allow effective and easy movement. For example, if you build up your bicep (upper arm) muscle but neglect to stretch it as well it will be very hard or impossible to straighten your arm. Yoga poses build strong lean muscles because they lengthen and strengthen. Yoga poses add to the strength of the muscles isometrically by using the body weight to work against gravity as in the Plank Pose and isotonically by dynamic movements as in Sun Salutations.
Muscles work in pairs, as one muscle contracts on one side of a joint there must be its counterpart on the other side lengthening to allow the movement. For example, in order to come into a standing forward bend we need to contract our abdominal muscles to bring the torso closer to the legs and at the same time we need to have sufficient length in our back muscles to allow the body to bend. For friction free action both pairs of muscles need to be well-matched in length and in strength.
In our everyday life we tend to perform repeated movements which can lead to certain muscles becoming dominant and thus expose the joints to wear and tear, the muscles or tendons can become inflamed and too painful to stretch. Yoga addresses imbalances in strength and flexibility in the right and left sides of the body, the upper body and lower body and the front and the back of the body.
As we hold an asymmetrical yoga pose such as the Lateral Angle Pose we keep our attention on the joints, muscles and breath. We notice if the breath is laboured meaning that we need to ease off and slowly build up our muscular endurance. We notice if our joints feel compressed meaning that we need to engage our postural muscles and lift up out of the joint. We notice how much length we have in our muscles to allow us to stretch into the pose. We notice all this on one side of the body and then compare it to the other side and with this knowledge we can work on equalising the strength, length and endurance of our muscles.
One of the key features of yoga poses is we build complete awareness of how our body and mind is acting and reacting and adjust our practice accordingly. This is called listening to your body.