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Muscle Anatomy 101 Pt2
Muscle Anatomy 101 Pt2
Muscle Anatomy 101 Pt2
Muscle Anatomy 101 Pt2
Muscle Anatomy 101 Pt2
Muscle Anatomy 101 Pt2
Muscle Anatomy 101 Pt2
Muscle Anatomy 101 Pt2
Muscle Anatomy 101 Pt2
Muscle Anatomy 101 Pt2
Muscle Anatomy 101 Pt2
Muscle Anatomy 101 Pt2
Muscle Anatomy 101 Pt2
Muscle Anatomy 101 Pt2
Muscle Anatomy 101 Pt2
Muscle Anatomy 101 Pt2
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Muscle Anatomy 101 Pt2

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  • 1. Muscle Anatomy 101 Part II
  • 2. Muscle Contraction <ul><li>Huxley Sliding Filament Theory </li></ul><ul><li>Briefly- actin slides over myosin causing the z-lines to pull together; thus shortening the sarcomere </li></ul>
  • 3. <ul><li>Action potential travels to neuromuscular junction </li></ul><ul><li>Acetylcholine (Ach) is released </li></ul><ul><li>Sarcolema is depolarized </li></ul><ul><li>Muscle fiber is excited </li></ul><ul><li>Ca++ is released from sarcoplasmic reticulum </li></ul><ul><li>Ca++ binds to troponin </li></ul><ul><li>Myosin heads bind to actin </li></ul><ul><li>Powerstroke occurs </li></ul><ul><li>ATP binds to crossbridge </li></ul><ul><li>Myosin detaches from actin </li></ul><ul><li>If Ca++ and ATP are present cycle occurs again if physically possible </li></ul>
  • 4. Muscle Contraction <ul><li>Relaxation occurs when stimulus stops </li></ul><ul><li>Ca++ is actively pumped back into SR </li></ul><ul><li>ATP is required for excitation and relaxation </li></ul>
  • 5. Size Principle <ul><li>“Motor units are recruited from the smallest to the largest based on the force demands placed on the muscle.” </li></ul><ul><li>Smaller (lower threshold) units are recruited first (predominately Type I) </li></ul><ul><li>Based on force demands larger (higher threshold) units are recruited (predominately Type II) </li></ul>
  • 6. Size Principle <ul><li>*Important Training Concept* </li></ul><ul><li>Low resistance = smaller units = 12-15RM </li></ul><ul><li>High resistance = larger units = 1-5RM </li></ul><ul><li>*Only recruited units benefit from training* </li></ul>
  • 7. All-or-None Law <ul><li>“When a specific motor unit reaches its threshold level for action, all of the muscle fibers in that motor unit are activated fully.” </li></ul><ul><li>-Refers to individual unit NOT entire muscle </li></ul><ul><li>-Variation of force </li></ul>
  • 8. Muscle Activation & Training <ul><li>Different loads recruit different types and numbers of motor units </li></ul><ul><li>Heavier loads recruit more units </li></ul><ul><li>Exception to size principle: High velocity movements </li></ul>
  • 9. Muscle Activation & Training <ul><li>Recruiting low threshold first delays muscular fatigue for submax exercise </li></ul><ul><li>Neurons of high threshold units ability to recover quickly allows them to be activated quicker in repeated actions </li></ul>
  • 10. Muscle Activation & Training <ul><li>-To achieve training effect of Type II there must be high power output demands </li></ul><ul><li>-Recruitment order is generally fixed, may change due to body position </li></ul><ul><li>-exercising at various angles? </li></ul>
  • 11. Muscle Actions <ul><li>Concentric: active shortening (m. force > resistance) </li></ul><ul><li>Eccentric: lengthening (m. force<resistance) </li></ul><ul><li>Isometric: static (m. force=resistance) </li></ul>
  • 12. Muscle Actions <ul><li>Ascending Curve: force gets greater throughout ROM </li></ul><ul><li>Descending Curve: force greatest at beginning </li></ul><ul><li>Bell Curve: force greatest in middle </li></ul>
  • 13. Length-Tension (Force) Curve <ul><li>Optimal length at which muscle can generate force </li></ul><ul><li>Optimal length: maximal crossbridge interaction </li></ul>
  • 14. Force Velocity Curve <ul><li>“As the velocity of muscular movement increases, the force a muscle is able to develop concentrically decreases” </li></ul><ul><li>-The greater the force the slower the movement (concentrically) </li></ul><ul><li>*Opposite true for eccentric muscle actions </li></ul>
  • 15. Force Velocity Curve <ul><li>High force development is related to tissue damage </li></ul><ul><li>-Muscle soreness after eccentric exercise </li></ul>
  • 16. Questions?

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