Muscle Tissue Properties Irritability or Excitability …to be stimulated Contractility …to contract (shorten) Extensibility …to be stretched Elasticity …return to original position after being stretched
Muscle Terminology Origin proximal attachment least moveable end closest to the midline of the body Insertion distal attachment most moveable end furthest from the midline of the body Action The movement at the joint when the muscle(s) contract
Concentric contraction Length of muscle shortens Muscle force is greater than the resistance If lifting 50 pounds and the muscle generates more than 50 pounds the muscle with shorten and move the weight. Static or Isometric contraction No change in muscle length Muscle force is equal to the resistance Lifting 50 pounds and the muscle generates 50 pounds of force Eccentric contraction Muscle lengthens Muscle force is less than the resistance Lowering 50 pounds and the muscle generates less than 50 pounds
Eccentric Contraction Used to control agonist and prevent over lengthening of the antagonist. Example: triceps lowers dumbbell while biceps ’controls’ the triceps activity (action). Causes more damage than other types Greater repair required… …producing a stronger muscle Also, results in more muscle soreness.
ROLE OF MUSCLES Agonist prime mover Antagonist action opposite to the agonist Stabilizers fixate or stabilize the joint Synergists assist or guiding
Agonist and Antagonist Antagonist Agonist Antagonist
TABLE 2.1Type of Contraction Isometric Isotonic ConcentricEccentric Agonist muscleNo changeShorteningLengthening AntagonistNo changeLengtheningShortening Joint angleNo changeDecreaseIncrease Direction of body partAgainst immovable object Against gravity or external force Consistent with gravity or external force MotionPressure but no motionCauses motion DescriptionStaticDynamic shorteningDynamic lengthening Muscle force v. Resistance F = RF > RF < R
Determination of Muscle Action Muscle location Origin and insertion What joint(s) it crosses Planes and their actions Most muscle can not perform opposite actions (e.g. flexion AND extension) Line of pull Muscles only pull on bones, they do not push bones! Insertion is pulled towards the origin
Joint Actions What joint does the muscle cross? Where does the muscle cross the joint e.g. anterior, lateral, etc. If the insertion end of the muscle is pulled towards the origin end, what action would result at the joint?