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