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
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
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
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
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)