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Factors Affecting Muscle Force

fiber type - fg, fog, so # of units stimulated frequency of firings temperature elasticity. length/tension force/velocity power (P=Fv) angle of pull. Factors Affecting Muscle Force. 1. MUSCLE FIBER TYPES. FG - fast glycolytic - HIGH Force, low aerobic

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Factors Affecting Muscle Force

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  1. fiber type - fg, fog, so # of units stimulated frequency of firings temperature elasticity length/tension force/velocity power (P=Fv) angle of pull Factors Affecting Muscle Force

  2. 1. MUSCLE FIBER TYPES • FG - fast glycolytic - HIGH Force, low aerobic • FOG - fast oxidative glycolytic - HIGH Force, medium aerobic • SO - slow oxidative - low force, HIGH aerobic

  3. 2. # OF UNITS STIMULATED • Force increases as the number of motor units being stimulated increases • Standard order of recruitment of fibers:1st SO, 2nd FOG, last recruited are FG

  4. 3. FREQUENCY OF FIRING • Generally, as the frequency of nerve stimuli increases in the motor units, the Force increases • Highest level of Force achieved in long-length muscles at lower levels of firing frequency

  5. 4. MUSCLE TEMPERATURE • Warmth deep in the muscle allows for faster contractions as well as faster relaxation • Warm muscle has less resistance to quick changes in length

  6. 5. ELASTICITY 1st tension developed in muscle 2nd muscle is quickly stretched then shortened • Net Result = INCREASED Force • examples:windup, impact on landing before takeoff

  7. 6. LENGTH/TENSION • Direct relationship • resting length or slightly stretched =  Force • shortened state =  Force (less F generated)

  8. 7. FORCE/VELOCITY • Indirect relationship • as speed of contraction increases • Force of contraction decreases

  9. 8. POWER • P = Fv • trade-off between F and v • approx. 30% of max. contraction speed results in most power

  10. 9. ANGLE OF PULL • 90º angle = 100% rotary • less than 90º angle = more stablizing • more than 90º angle = more dislocating

  11. SENSORY UNIT • sensory receptors • axion • nerve cell

  12. PROPRIOCEPTORS • internal receptors • in and around joints • near skin • inner ear • perceive body’s movements and positions

  13. GOLGI TENDON ORGANS“Relax, Don’t Fight It” • located in ________ • stretch activates two things:1. _____________________2. _____________________ • PNF involves Golgi Tendon OrgansProprioceptive Neuromuscular Facilitation

  14. MUSCLE SPINDLES • Located ______________________ • stretch = promotes contraction of agonist = inhibits antagonist contraction • e.g. “Knee Jerk”, Windup in throwing/striking

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