Chronic Musculoskeletal Adaptations to Exercise

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Introduction[edit | edit source]

Effects of Deconditioning[edit | edit source]

Decrease in:

  • Muscle mass (skeletal and cardiac)
  • Muscle strength (skeletal and cardiac)
  • Cardiovascular system function
  • Total blood volume
  • Plasma volume
  • Heart volume
  • Orthostatic tolerance
  • Exercise tolerance
  • Bone mineral density

Reversibility Principle[edit | edit source]

  • Benefits of training are transient and reversible
    • After 2 weeks of detraining
      • Measurable reduction in work capacity

Musculoskeletal Adaptations[edit | edit source]

Resistance Training[edit | edit source]

  • Resistance training yields substantial strength gains via neuromuscular changes
  • Important for overall fitness and health
  • Critical for athletic training programmes

Gains in Muscular Fitness[edit | edit source]

  • After 3 to 6 months of resistance training
    • Learn to more effectively produce force
    • Learn to produce true maximal movement
    • Young men experience greatest absolute gains versus young women, older men, children
    • Due to incredible muscle plasticity
  • Strength gains result from
    • ↑ muscle size
    • Altered neural control

Neural Control[edit | edit source]

  • Strength gain cannot occur without neural adaptations via plasticity
    • Strength gain can occur without hypertrophy
    • Property of motor system, not just muscle
  • Motor unit recruitment, stimulation frequency, other neural factors essential

Strength training module - add info or image?

Mechanism of Muscle Strength Gain[edit | edit source]

Motor Unit Recruitment[edit | edit source]
  • Normally motor units recruited asynchronously
  • Synchronous recruitment leads to strength gains
    • Facilitates contraction
    • May produce more forceful contraction
    • Improves rate of force development
    • Increased capability to exert steady forces
  • Resistance training leads to synchronous recruitment
  • Strength gains may also result from greater motor unit recruitment
    • Increased neural drive during maximal contraction
    • Increased frequency of neural discharge (rate coding)
    • Decreased inhibitory impulses
  • Likely that some combination of improved motor unit synchronisation and motor unit recruitment results in strength gains
Autogenic Inhibition[edit | edit source]
  • Normal intrinsic inhibitory mechanisms
    • Golgi tendon organs
    • Inhibit muscle contraction if tendon tension too high
    • Prevent damage to bones and tendons
  • Training can decrease inhibitory impulses
    • Muscle can generate more force
    • May also explain superhuman feats of strength
Muscle Hypertrophy[edit | edit source]
  • Hypertrophy = increase in muscle size
  • Transient hypertrophy (after exercise bout)
    • Due to oedema formation from plasma fluid
    • Disappears within hours
  • Chronic hypertrophy (long term)
    • Reflects actual structural change in muscle
    • Fibre hypertrophy, fibre hyperplasia, or both
Fibre Hypertrophy[edit | edit source]
  • More myofibrils
  • More actin, myosin filaments
  • More sarcoplasma
  • More connective tissue
  • Resistance training → ↑ protein synthesis

Resources[edit | edit source]

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References[edit | edit source]