Physiological effects of training

The cardiovascular system

The cardiovascular system

• Thought to have the most influence on performance of an athlete.

• Primary function is to transport O2 from lungs to blood & CO2 from tissues to lungs.

Splenic reserve• Horse have high O2 consumption, greater than other animals

due to large splenic reserve of red blood cells.• Adrenaline stimulates the spleen during exercise & RBC are

quickly added to circulation.• This gives extra haemoglobin & oxygen capacity.• Makes for an efficient athlete.

Response of the heart to exercise

• Stroke Volume• = volume of blood ejected from the cardiac

ventricles with each contraction (vol of blood leaving the heart per beat).

• Increase in cardiac output is main way horse increases O2 uptake during exercise.

• Resting stroke vol. is about 800-900ml. Can increase to 1700ml in fit TB’s in maximal work.

The heart• Trained horse has a

larger heart mass, as training causes hypertrophy of the heart muscle.

• Hypertrophy is rapid response occurring within 2 months of training.

• Training any longer than this makes no difference to heart size.

Cardiovascular responses to training

• Increase in heart size.• Adaptation of the working heart rate. • Training believed to result in faster heart rate recovery

after work• Increase in total RBC vol. occurs, creating greater potential

for O2 transport capacity – due to splenic reserves• Increased plasma volume.• Blood pressure is lower during exercise because CV system

does not work so hard to get the same result• Increase in capillarisation of the muscles.

Revision Questions – cardiovascular1. What is the normal heart rate for an average adult horse at rest?2. What is the maximum heart rate of a horse?3. What happens to blood flow priorities during exercise?4. What demands are placed on the cardio-vascular system with an

increase in work?5. How does the heart adapt to training?6. Define “stroke volume”.7. Define “cardiac output”.8. What changes occur in the capillaries and why?9. What can happen to the plasma & blood cell volume with training?10. As the horse gets fitter, what changes will occur to his heart &

respiratory rate during work?11. What will the changes be after work in the fitter horse?12. What happens if not enough oxygen can be provided to the muscle

cells?13. What is the effect of lactic acid in the muscles?