Unit 2 part 2

• Other factors influencing force generation (2)

  Muscle environment (temp, ph, hydration, energy supply)

  Muscle fiber type and muscle architecture ( connective tissue attachement influence force transmission)
• Primary factors influencing force generation (3)

  Length of the muscle fiber

  Frequency of stimulation (twitch vs tetanus types) (neural effect)

  Number of muscle fibers that have been stimulated (neural effect)
• Tension types

  Active: generated by active mechanisms like cross bridge cycling

  Passive: generated when muscle is stretched beyond its resting length due to elastic elements within the muscle/tendon tension arises in the absence of muscle contraction
• How greater ap frequency gives greater peak tension


  Muscle twitch: troponin to shift cuz of calcium release which goes back to SR almost immediately after it released

  Tetanic contractions: Aps are sent before calcium can return to SR so tropomyosin doesn't shift back resulting in my myosin binding sites, more time for cross bridge cycling and finally greater muscle tension
• Tetanus


  A maintained muscle contraction in response to repetitive stimulation

  Motor units are recruited on a Rotating basis

  Unfused: the muscle fiber has time to partially relax between contraction/stimuli

  Fused: the muscle fiber does not have time to relax between contraction/stimuli resulting in maintained muscle tension
• Summation


  The increase in muscle tensions arising from successive action potentials
• Frequency tension relationship

  Positively related

  AP last 1-2ms generated tension can last over 100ms

  The closer the action potentials the greater the resulting peak tension
• As load increases (3)

  The less the muscle can shorten

  The slower the shortening velocity d/t

  The longer the latent period
• Isotonic vs isometric

  Isotonic is concentric so muscle tension is greater than the load which results in shortening the muscle length

  Isometric is when the muscle tension and load are equal so there is no change in muscle length
• Factors effecting changes in muscle length (5)

  Weight/force of the load

  Amount of force generated by the muscle

  Initial length of the muscle fiber

  Frequency of stimulation

  Number of motor units recruited
• Load


  The force exerted on the muscle by an object (usually its weight)
• Muscle tension


  The force exerted on an object by a contracting muscle

  Can be created by force muscle
• Eccentric contraction


  muscle lengthens
• Isometric contraction


  Tense muscle in steady position
• Concentric contraction

  Muscle shortens