Effects of deconditioning on type 2 / FT fibres

• Effects of deconditioning on type II / fast twitch fibres:

  • results in loss of force production
• Detraining / Deconditioning:

  • Atrophy: main cause of deconditioning in type 2 fibres - Affects both type 1 & type 2 fibres
• Atrophy:

  • net deficit of contractile proteins
  • this causes fibre shrinkage
  • reducing muscle mass
  • causing a decrease in force
  • leading to functional implications
• • human muscle produces 3 to 8kg force /cm^2
  • Less mass = less cm^3 = less force output
• Effects of deconditioning on type 2 fibres:

  • main effect is atrophy: a decrease cross sectional area leading to a decrease in force capacity
  • fibre population shift from type 2a to type 2x fibres
• Functional problems:

  • difficulty generating significant force fast enough e.g in response to balance disturbance - increasing risk of falls
• Atrophy & disuse v. pathology:

  • Disuse is a primary cause of atrophy, but pathological causes exist too
  • There are a number of pathologies which tend to promote atrophy
  • Thought to be linked to the inflammatory components of the disease process
  • Atrophy a common component of chronic conditions such as chronic heart failure, COPD, renal failure, obesity, hypertension and type 2 diabetes
  • Atrophy is also end result of inadequate calories – link to social economics status in elderly or eating disorders