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Muscle fiber dysfunction

Muscle Fiber Dysfunction - a general term used to encompass all commonly noted changes resulting from excessive stress to a muscle fiber, and the clinically observable phenomenon that result from those changes.
  • The term "muscle fiber dysfunction" has been chosen to describe this is a neuromyofascial phenomenon to separate the subject matter from information that may explain dysfunction originating from damage to a joint (e.g. arthritis), damage to a nerve (e.g. neuropraxia) or damage to fascia (e.g. fasciitis).
Observable Phenomena Associated with Muscle Fiber Dysfunction:
  • Increased tone (over-activity)
    • General increase in tissue density
    • Resistance to stretch
    • Changes in EMG activity
    • Changes in muscle spindle activity (H-reflex)
    • Twitch response
  • Taut bands
  • Palpable nodules
  • Myalgia
    • Pain upon deep palpation
    • Latent trigger points (tender points)
    • Active trigger points
    • Referral pain
    • Diffuse myofascial pain and allodynia
  • Centralization
    • Whiplash syndrome
    • Chronic low back pain
    • Fibromyalgia syndrome

Pathobiology of Muscle Fiber Dysfunction:

  1. Excessive Stress
    • Acute tissue trauma
    • Continuous low-load activity
      • Postural dysfunction
    • Eccentric contractions
  2. Insufficient blood flow
    • Capillary restriction (especially during isometric contraction)
    • Insufficient recovery (cycling of motor units is insufficient)
  3. Metabolic crisis
    • Hypoxia
    • cytochrome c oxidase deficiency
    • Mitochondrial, sarcotubular system and cell membrane changes
    • Moth-eaten fibers and degeneration
  4. Muscle fiber changes
    • Taut bands and palpable nodules
    • Type I fiber hypertrophy
    • Increase in Type IIA fibers
    • Increase in transitional fibers
    • Preferential loss of Type I and/or Type II motor units
    • Infiltration of adipose and/or connective tissue
  5. Chemical change
    • Markers of inflammation and pain
    • Acidity (pH)
    • Excessive Ca2+
    • Excessive acetylcholine (ACh)
  6. Nervous system adaptation
    • Altered reflex sensitivity
    • Dorsal horn reorganization
    • Hippocampus inhibition
    • Autonomic system involvement
  7. Centralization