Factors Affecting Muscle Force 1.fiber type - fg, fog, so 2.# of units stimulated 3.frequency of firings 4.temperature 5.elasticity 6.length/tension 7.force/velocity 8.power (P=Fv) 9.angle of pull

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

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

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

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

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

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

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

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

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

SENSORY UNIT 1.sensory receptors 2.axion 3.nerve cell

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

GOLGI TENDON ORGANS “Relax, Don’t Fight It”  located in ________  stretch activates two things: 1. _____________________ 2. _____________________  PNF involves Golgi Tendon Organs Proprioceptive Neuromuscular Facilitation

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