Muscle Fiber Dysfunction

Muscle Fiber Dysfunction: Muscle fiber dysfunction isa 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 as 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
   
   
   

For more information, please refer to our course and systematic review -
Muscle Fiber Dysfunction and Trigger Points