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Lecture Notes - W. Nov 20

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York University
Kinesiology & Health Science
KINE 2031

Lecture – November 20, 2013 Muscles Smooth muscle •Not give a striated appearance •Individual fibers are not parallel •You find these smooth muscles around fluid structures over the body •Glands, GI track, anytime there is compression to move fluid Cardiac Muscle •Striated •Non parallel muscle fibers •Fiber arrangement similar to smooth muscle •Ends are called intercalated discs Skeletal muscle action •Movement or non movement - two distinct types •Isometric - no movement •Concentric - movement: shortening contraction o origin muscle tendon attaches to our trunk o Insertion: distal attachment of the muscle o The distance between origin and insertion has decreased •Eccentric - movement: lengthening contraction o There will be a question on THIS! o Understanding this concept is important •When your shortening your biceps (elbow flexion/concentric) and then when you do elbow extension - its NOT triceps which controls the movement it is the BICEPS lengthening o Gravity makes up for the extension o So you have shortening contraction - concentric o Lengthening contraction - eccentric •Another example: When you elbow extend initially you are shortening triceps and when you do elbow flexion you are lengthening triceps o You have to think of the types of resistance and who is producing movement Levers •A lever has mass, and gravity would want to pull it down, it has length and can rotate o Mass, length, rotate •Fulcrum is what the lever rotates on •Three classes of levers: o Teeter totter - First class lever • Fulcrum in the middle, force is mass, resistance due to gravity • Fulcrum in the length of the lever not in the end • Resistance has a center of gravity • Effort is the action of the muscles • We define distance from the fulcrum • Effort arm - distance from fulcrum from the application of effort • Resistance arm - distance from fulcrum from the resistance • Example: head resting on the cervical vertebrae , the front of your head muscles is the resistance and the force applied in the back - thus the head is elevated • Not many examples of this on your body o Wheel barrow - second class lever • Fulcrum is at the end of body • Resistance in the middle • Effort to elevate past the resistance - further way from the fulcrum • Example: foot in standing position and your are going up in your toes  So the fulcrum on your toes, mass is the leg • Not many examples of this o Third class lever • Fulcrum again in the end of the lever • Effort is in the middle • Example: arm the center of gravity is somewhere in the fore arm  Effort tends to be close to fulcrum • Example: hip flexion • Mechanical advantage o Amount of force you apply, times distance over the lever where the force is applied (force arm) which equals resistance times, resistance arm o F x FA = R x Ra o You can actually calculate the numbers of what will happen - will learn in another class • Lever system in our arm o Levers are your long bones - limbs
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