Functions during exercise

1
Functions during exercise

• stroke volume - amount of blood pumped during
  each systole
• 33 increase during exercise
• maximal stroke volume and maximal heart rate do
  not always coincide
• ? intense exercise

2
Cardiac output/blood pressure

• amount of blood pumped by the heart each minute
• HR X SV Q
• majority of increase in Q is due to increased HR,
  small increase in SV
• blood pressure varies
• HR
• blood volume
• ventricular contraction
• resistance of blood flow
• normal systemic blood pressure in horse
• 135/95 to 155/110
• pulmonary blood pressure much lower
• less force of contraction, less resistance to flow

3
Total Blood Volume

• critical index of a horses fitness
• factors contributing to total blood volume and
  hemoglobin
• breed, age, bodyweight, training sex
• training
• sprint trained animals have lower Hg levels and
  PCV than endurance trained animals
• ? - more aerobic work stimulates more production
  of RBC by bone marrow

4
Blood Circulation

• onset of exercise
• some plasma diffuses from blood to tissue
• blood becomes more viscous
• high PCV
• O2 carrying capacity increases due to increased
  of RBC per unit of blood
• shift of blood from other body parts to
  exercising muscle tissue
• 15 to 85 to muscle
• assists in thermoregulation
• diaphragm

5
Effects of Conditioning

• cardiovascular changes occur quite rapidly (2
  months)
• resting HR - no change
• maximal HR - no change
• heart rate lower following conditioning to do
  same workload as unconditioned
• HR returns to resting value faster with
  conditioning
• endurance conditioning increases plasma volume
  20 and hemoglobin concentration 34 (increased
  SV)
• sprint conditioning - greater increases in PCV,
  RBC, and hemoglobin then endurance conditioning
  (resting)