Muscular Fatigue

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Muscular Fatigue

• reduces pool of fibers available to contract and
  force
• 1. lactate accumulation
• 2. glycogen depletion
• lactate accumulation
• high intensity exercise
• increased muscle lactate
• reduces pH (acidic)
• muscles fail to contract
• decreases rate of energy production
• lactate accumulation in FG fibers first
• reduction of power
• light exercise hastens removal

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• glycogen depletion
• not the fatigue factor for high intensity work
• low intensity work
• depletion reflects recruitment pattern
• ST - first to fatigue
• FOG fibers second
• FG may eventually deplete
• as one fiber type is depleted the next is
  recruited
• fibers dependent on fats for energy
• decreased rate of energy production
• must slow speed
• fatigue before completely out of adipose tissue
• repletion of glycogen
• 2 days
• reverse order of recruitment

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• ability to perform is limited by onset of fatigue
• impairment of muscle function
• depletion of substrate
• disruption of energy production
• electrolyte gradients
• alteration of calcium uptake and release by SR
• decrease blood flow and/or too much temperature
  increase in muscles

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Diseases

• muscle strain
• over-stretched muscle
• increases heat (increased blood flow)
• swelling from fluid accumulation
• pain
• rest and cold hydo-therapy
• recovery time
• days to weeks
• test for muscle damage
• CK

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• Exertional Rhabdomyolysis- tying up, azoturia
• exercise induced damage to muscle
• mild cramping to inability to move
• common conditions
• well conditioned horse
• after day or two rest and full feed
• over exercised
• fluid/electrolyte imbalance- dehydration
  (decreased chloride and calcium)
• deficiency of selenium and /or Vit E
• hormonal effect
• high strung
• female
• genetic predisposition

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• symptoms
• stiff gait to not moving at all
• if down, unable to get up
• muscles of hind quarters and back most affected
• shoulder muscles
• muscle feel rigid deep palpation causes pain
• distressed, sweating, increased temperature,
  increases RR and increases HR

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• treatment
• limit muscle damage
• restore fluid and electrolytes
• relaxants/pain relievers
• keep warm and still
• mild cases - walk
• prevention
• change diet
• training
• often reoccurs