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

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

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

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

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

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

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