part7b1A

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part7b1A

  1. 1. CHAPTER 11<br />MUSCLE<br />
  2. 2. MECHANICS OF SINGLE-FIBERCONTRACTION<br />GROUP 2 YA<br />
  3. 3. TENSION – is the force exerted on an object by a contracting muscle<br />LOAD - the force exerted on the muscle by an object<br />Muscle tension and load are opposing forces.<br />
  4. 4. ISOMETRIC - are contractions in which<br />the muscle is developing force but not shortening and no visible movement is seen<br />e.g. weight lifting, sprinting<br />ISOTONIC - a muscle is generating a<br />constant force to move a load<br />e.g. jogging, dancing, aerobics<br />
  5. 5.
  6. 6. TWO TYPES OF ISOTONIC CONTRACTION<br />CONCENTRIC ISOTONIC - the muscle is shortening while it is contracting<br />e.g. picking up an object<br />ECCENTRIC ISOTONIC - the muscle is lengthening while it is contracting<br />e.g. lowering the object back to place<br />
  7. 7. TWITCH CONTRACTION<br />TWITCH - is a single stimulus contraction–relaxation sequence in a muscle fiber<br />
  8. 8. THREE PHASES OF TWITCH CONTRACTION<br />1. LATENT PERIOD - lasts about 2 msec (milliseconds)<br />and is the time between stimulation of muscle cells and force generation<br />2. CONTRACTION PERIOD - lasts about 10–100 msec<br />and is the period during which force (measured in grams) is increasing<br />3. RELAXATION PHASE - the period when force is <br />decreasing; lasts 10–100 msec<br />
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  10. 10.
  11. 11.
  12. 12. Isotonic twitch depends on the magnitude<br />being lifted<br />Heavier loads:<br /><ul><li>Latent period is longer
  13. 13. Velocity of shortening is slower
  14. 14. Duration of a twitch is shorter
  15. 15. Distance shortened is less</li></li></ul><li>
  16. 16. LOAD-VELOCITY RELATION<br />Velocity at which a muscle fiber shortens decreases<br />with increasing loads<br />
  17. 17. The shortening velocity is maximal when there is no<br />load<br />Zero when the load is equal to the maximal isometric<br />tension<br />Loads greater than the maximal isometric tension, the<br />fiber will lengthen at a velocity that increases with load<br />

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