Training and Re-conditioning Type 2 fibres

• De-conditioning is reversible

  Provided an adequate physiological stress / challenge is presented
• What counts as an appropriate Physiological stress for FT fibres?

  • F = 2 to 3 times per week
  • I = 60% to 80% 1RM for 8 to 12 reps
  • T = 2 to 4 sets
  • T = resistance
• Type II training effect:

  • hypertrophy
  • hyperplasia
  • fibre conversion from type 2x to 2a
  • increase glycogen stores
  • increase glycolytic enzymes
• Hypertrophy

  • increase in fibre size = increase in muscle bulk (cross sectional area)
  • increase in synthesis of contractile proteins = an increase in volume of actin & myosin
  • leading to more crossbridge formations
  • higher force capacity
• • human muscle produces 3-8kg force /cm^2
  • increasing mass/cross sectional area = increased force output
• Hyperplasia

  • is the increase in fibre numbers
  • Due to splitting of pre-existing fibres or creation of new fibres following damage
  • Any new fibres can then be hypertrophied
  • Unlikely to happen to the vast majority of people
• Use of anabolic steroids can enhance physiologically gained hypertrophy & underpin hyperplasia - however the following may also occur:

  • men: sperm count, infertility, shrunken testes, baldness, breast development, increase risk Ca prostate, splayed teeth, forehead overgrowth, severe acne
  • women: facial / body hair, loss of breasts, swelling of the clitoris, a deepened voice, increased sex drive, dysmenorrhoea, headhair loss, severe acne
• In addition, both men and women who take anabolic steroids have increased risk of:

  • heart attack or stroke
  • liver or kidney tumours
  • Hypertension
  • thrombi
  • fluid retention
  • high cholesterol
  • Psychological effects e.g aggressive behaviour, mood swings, mania, hallucinations, delusions
  • addictions
• Fibre transformation:

  • Possible – but likely to be limited
  • Majority of response to conditioning occurs via hypertrophy rather than by conversion
  • Mainly because:
  • The correct prescription for conversion not known – so prescription difficult
  • And fibre plasticity is genetically determined so response to any prescription will be varied
• Time Frames:

  • Any sudden increases in ability to do a strength task is likely to be due to motor learning
  • For hypertrophy to be significant it takes ~ 8 weeks /52 of resistance training