Adaptations to Resistance Training

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Adaptations to Resistance Training
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Motor Unit

• One motor neuron and all the muscle fibers it
  innervates
• Types
• ST
• FTa
• FTb
• Order of recruitment

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Overview of Adaptations
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Increase IEMG

• IEMG integrated electromyography
• Increase in IEMG due to an enhanced ability to
  recruit motor units.
• Changes are greater with eccentric training

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Increase Motor Unit Firing Rate
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Recruitment of High-Threshold (FT) Motor Units

• Enhanced recruitment of high-threshold motor
  units
• Increased time that high-threshold motor units
  can be activated

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Motor-Unit Coordination

• Neural Facilitation of Movement
• develop reflexes to sudden high stretch loads
• Co-contraction of antagonists
• control of flexors and extensors

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Motor-Unit Coordination

• Synchronization of MU firing rates
• Cross-training
• contralateral limb
• 36.4 increase in trained limb ? 24.7 increase
  in inactive limb
• Neural disinhibition
• Golgi tendon organ
• Hypnosis
• Injury and surgery

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Contractile Components of Strength

• Whole muscle hypertrophy
• Muscle fiber hypertrophy (95-100 of whole muscle
  hypertrophy)
• Increase in number of myofibrils
• Muscle fiber hyperplasia (0-5 of whole muscle
  hypertrophy)
• Muscle fiber pinnation angles

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Myosin Heavy Chain IIb

• Conversion to slower fiber type (IIb to IIx or
  IIx to IIa)
• More economical. Fewer cross-bridge cycles or
  power strokes per fiber contraction.

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Aerobic Capacity

• Same number of mitochondria in a larger fiber ?
  decrease mitochondrial density
• Also, a decrease in capillary density slower
  substrate delivery (oxygen, glucose, etc.)

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Anaerobic Capacity

• Increase glycogen, PCr, ATP, and ADP
• No change in enzyme concentration but there is an
  increase in enzyme activity

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Muscle Elastic Component of Strength

• Stretch shortening cycle
• Series - tendons and cross bridges
• Parallel - membranes
• Stretch shortening cycle and performance
• Muscle fatigue is accompanied by a decrease in
  the performance of the stretch shortening cycle

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Coordination

• Neural-motor
• Contractile
• Elastic

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Delayed Onset Muscle Soreness

• Damage
• Edema and inflammation
• Increased cell tension from edema, prostagladins
  and histamine
• Additional muscle tissue breakdown due to
  proteases, phospholipases and oxygen radicals
• Cell repair formation of protective proteins
  that prevent muscle soreness during subsequent
  workouts.