Having a solid understanding of muscles, their movements and function in relation to yoga poses is essential to better understanding the movement of the body and the relationship between the muscles, the tendons and the skeletal structure. This knowledge is invaluable in helping to prevent injury to oneself or students during practise.
There is a common language of terms used in the sport and medical fields which describe the movement and the resulting action of the muscles. Below are the more common terms in use with a brief description of the movement.
Abduction: this describes the moving of a body part away from the mid-line of the body or from another part of the body.
Adduction: this describes the moving of a body part towards the mid-line of the body or towards another part of the body.
Extension: this describes the action of straightening a body part.
Extensor: this refers to any muscle that extends (straightens) a body part away from the body.
Flexion: this describes the action of bending of a joint.
Flexor: this refers to a muscle that reduces the angle between two bones for example bending the arm at the elbow or raising the thigh towards the stomach.
Retraction: the describes the movement of a body part in the posterior (backwards) direction. For example when the shoulder blades (scapular bones) are pulled back.
Protraction: this describes the movement of a body part in the anterior (forwards) direction. This is the opposite of retraction.
Rotator: a group of muscles that enable the rotation of a joint. For example, the hip and the shoulder.
Vertical plane: the imaginary vertical line that runs from head to toe when standing upright.
Lateral: this describes an area on the side of the body or a sideways movement. For example, to describe something located on the sides or extending towards the sides, away from the body.
Medial: this describes an area located on the middle of the body or extending towards the middle of the body.
Profile: to view a part of the body from the side.
Neutral position of the spine: this refers to a position of the spine that resembles an S-shape when viewed from the side (in profile).
Isotonic: these are contractions that cause the muscle to change in length as it contracts to cause movement in the body part. The two types of contraction are Concentric and Eccentric.
Concentric: this type of contraction causes the muscle to shorten as it contracts and is the most common type of contraction. For example, bending the elbow from straight to fully flexed causes a concentric contraction of the Biceps Brachii muscle.
Eccentric: these contractions are the opposite of concentric contractions and occur when the muscle lengthens as it contracts. For example, when kicking a ball, the Quadriceps contracts concentrically to straighten the knee whilst the Hamstrings contract eccentrically to slow the motion of the lower leg.
Isometric: these are contractions that occur when there is no change in the length of the contracting muscle. For example, holding still in Utthita chaturanga dandasana pose (extended/high Plank). The muscles of the core, back, legs and arms are all engaged to hold the position but without causing any movement of the limbs or joint. This strengthens and stabilizes the muscles being used.
Lisa Harte – Tirisula 200 TT Blog 2 – 19th May 2017