Muscle Mechanics

Question 1

Isometric Contraction

Answer 1

• means “Same Length”
• Contraction at same length: muscle ends are fixed
• Holding weight w/o moving
• Small stim: small # contracting fibers
• Big Stim: large # contracting fibers
  
  • B/c electricity stims more fibers
• Max force is when all fibers stimulated
• Twitches can sum

Question 2

Tetanus

Answer 2

• Unfused
  
  • Multiple stim can build up force in cyclical fashion
  • stim spaced farther apart in time
• Fused:
  
  • Multiple rapid stimulation causes smooth increase to max force

Question 3

Isotonic Contraction

Answer 3

• “Same Force”
• Allow ends of muscle to move
• Movement depends on initial length and load
• Takes longer to generate force to move heavier afterload
  
  • Slower and less far
  • Due to loss of cross bridges
  • As muscle shortens # of cross bridges decreases and only goes until unough to support the load
    
    • Takes more to support bigger load so can’t go as far before losing necessary # of cross bridges

Question 4

Slow Oxidative Muscle Fibers

Answer 4

• Low slow myosin ATPase activity
• High oxidative capacity (many mitochondria)
• Fatigue resistant: sustained contraction
• Postural muscles
• Red colored

Question 5

Fast Glycolytic

Answer 5

• High fast myosin ATPase activity
• High Glycolytic activity
• Fast fatiguing
• Short duration high force contractions
• Non-postural: ex. weight lifting
• Used intermittently
• Light/white colored

Question 6

Fast Oxidative

Answer 6

• Characteristics b/t slow ox and fast glyco
• High fast myosin ATPase activity
• Moderate oxidative capacity
• Moderate fatigue resistant
  
  • fatigue faster than slow ox
  • fatigue slower than fast gly