Muscle Review Lecture PDF

Muscle Review PT 8361 CCI Dr. Hiser, PT, DPT, PhD Thanks to Dr. Maring for original slide deck. Session Objectives 1. Describe various roles/terminology related to muscle function. 2. Practice applying the roles and terminology to specific movements. Muscle Cla...

Muscle Review PT 8361 CCI Dr. Hiser, PT, DPT, PhD Thanks to Dr. Maring for original slide deck. Session Objectives 1. Describe various roles/terminology related to muscle function. 2. Practice applying the roles and terminology to specific movements. Muscle Classification Skeletal: Voluntary; striated; act on bones to which they are attached to create forces necessary for human movement. Cardiac: Involuntary, striated and found in the walls of the heart (myocardium). Self- contracting and must be regulated to contract in a rhythm generated by pacemaker cells. Smooth: Involuntary, non- striated, moves internal organs such as the bowels and vessel walls. Under autonomic nervous system control. Clinically Oriented Anatomy. Moore, Dalley, Agur. 8 th Ed. 2018. Skeletal Muscles Origin: Muscle attachment that moves the least, generally more proximal. Insertion: Muscle attachment that moves the most, generally more distal. Movement: Muscles can contract in many different ways. We will initially focus on movements that occur when the insertion moves towards the origin. The bone or skeletal system can be considered a lever system; the muscles produce the force required to move the levers. Guyton and Hall. Medical Physiology. 14 th ed. 2021 Muscles – classified by number of joints they cross One joint muscle: covers one joint and therefore has an effect over that single joint. (e.g. vastus medialis) Two joint muscles: covers two joints (e.g. rectus femoris or biceps) and therefore has an effect on two joints. Multi joint muscles: covers multiple joints and therefore has an effect over several joints. (e.g. finger flexors). Guyton and Hall. Medical Physiology. 14 th ed. 2021 Muscle attachments Brachialis originates on the humerus and inserts on the ulna. So, what happens when it contracts or shortens? Roles of Muscles Agonist: A muscle that causes the motion. Also sometimes referred to as the prime mover. Antagonist: A muscle that moves the joint in the opposite direction than the movement caused by the agonist. Going back to the brachialis: For what motion is it an agonist? During what movement would we consider it an antagonist? Muscle Roles Synergist: muscles that help to create the movement either by assisting with the movement, neutralizing, or by stabilizing around a joint when a muscle is moving. In movements, you can talk about the prime mover(s) or the agonist versus synergist muscles. 1. When you flex the elbow with the forearm in supination, the biceps brachii is the prime mover. What muscles might assist with the motion and be synergistic? Muscle Roles (cont.) Synergist muscles may: Act conjointly (see previous example) Act as a neutralizer (e.g. cancel or prevent the undesired action of either the prime movers or secondary movers when performing an action). E.g. Contract the fingers with wrist extended or in neutral; internal rotators of the hip may fire to counter act the external rotation component of the sartorius during hip flexion. Act as a stabilizer or fixator. For example, the rotator cuff during shoulder movements contract to stabilize the head of the humerus while other muscles (e.g. deltoid) contract to move the humerus. Co contraction: sometimes the agonist and antagonist muscles around a joint fire simultaneously. Types of Contraction Isotonic: (same tone) Muscle tension remains unchanged and the muscle length changes. Concentric: tension remains the same and the muscle shortens (origin and insertion moves closer together). Eccentric: tension remains the same and the muscle lengthens (origin and insertion move apart). For example, during “lowering movements” in the direction of gravity. Isometric: (same length) Muscle fires but there is no movement at the joint and no change in the length of the muscle. Isokinetic: (same speed). Muscle contracts and shortens at a constant rate of speed. Usually requires special equipment that allow you to set the speed in degrees of motion per unit of time. Guyton and Hall. Medical Physiology. 14 th ed. 2021 Try this Perform a concentric contraction of your quadriceps (knee extension) Now contract your quadriceps eccentrically. Contract your quadriceps isometrically. Stand up, bend down and touch your toes. What muscles were firing – was it your abdominals or your back extensors?