1. Functions during exercise èstroke 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 èamount of blood pumped by the heart each minute èHR X SV = Q èmajority of increase in Q is due to increased HR, small increase in SV èblood pressure varies –HR –blood volume –ventricular contraction –resistance of blood flow ènormal 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 ècritical index of a horses fitness èfactors contributing to total blood volume and hemoglobin –breed, age, bodyweight, training & sex ètraining –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 èonset of exercise –some plasma diffuses from blood to tissue –blood becomes more viscous high PCV –O 2 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 ècardiovascular changes occur quite rapidly (2 months) èresting HR - no change èmaximal HR - no change èheart rate lower following conditioning to do same workload as unconditioned èHR returns to resting value faster with conditioning èendurance conditioning increases plasma volume 20% and hemoglobin concentration 34% (increased SV) èsprint conditioning - greater increases in PCV, RBC, and hemoglobin then endurance conditioning (resting)