Factors Affecting Muscle Force

1
Factors Affecting Muscle Force

1. fiber type - fg, fog, so
2. of units stimulated
3. frequency of firings
4. temperature
5. elasticity

1. length/tension
2. force/velocity
3. power (PFv)
4. angle of pull

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 fibers1st 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
• exampleswindup, 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

1. sensory receptors
2. axion
3. nerve cell

12
PROPRIOCEPTORS

• internal receptors
• in and around joints
• near skin
• inner ear
• perceive bodys movements and positions

13
GOLGI TENDON ORGANS Relax, Dont Fight It

• located in ________
• stretch activates two things1.
  _____________________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