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

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

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

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

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)