Equine Exercise Physiology

Question 1

splenic contractions do what for the horse during exercise?

Answer 1

increase hematocrit from 35 to as high as 65

Question 2

the relationship between heart rate and speed is _____. If the line is steeper it means ____, and if the line is not as steep it means____

Answer 2

linear

the horse is less fit

the horse is more fit

Question 3

what does a normal ECG of a horse during exercise look like?

Answer 3

it is all QRS complexes with no P waves because the heart is going so fast

Question 4

is an arrhythmia in horses common?

Answer 4

yes, especially when recovering from the race

Question 5

what is AV block?

Answer 5

there is not a QRS complex for every P wave so the SA and AV nodes are not communicating properly

Question 6

what is ventricular premature contraction?

Answer 6

an early heart beat originating from the ventricle and you get a wide or abnormal looking QRS complex. the ventricle goes rouge and doesn’t listen to the pacemaker. this is the one where if it happens several times in a row it can be super bad

Question 7

what is atrial fibrillation?

Answer 7

irregularly regular so you can’t predict when the next heartbeat is

Question 8

how do you test for damaged cells in the heart?

Answer 8

measure troponin levels in the blood and if there is more than normal in the blood it probably means there is something wrong with the cells of the myocardium

Question 9

when do you want to use the cardiac troponin test? (hscTnT)

Answer 9

2-6 hours after the race, peaking at around 4 hours

Question 10

______ are released during exercise which dilates the nasal cavity

Answer 10

catecholamines

Question 11

why does the head extend when galloping?

Answer 11

so there are fewer bends in airways between external nares and lungs

Question 12

where does most of the resistance come from in the airways? what is the greatest point of resistance?

Answer 12

from the nasal cavity

inside the nares at the nasal valve

Question 13

what is the guttural pouch used for?

Answer 13

it cools the blood going to the brain

Question 14

what cranial nerves are passing through the guttural pouch?

Answer 14

9, 10, 11, and 12

Question 15

horses experience ____ and _____ during intense exercise especially in thoroughbreds

Answer 15

hypercapnia, hypoxemia

Question 16

horses can’t increase ventilation after a certain point because

Answer 16

there is a coupling of ventilation and stride frequency

Question 17

what are the 3 forces associated with exercise helping to generate airflow?

Answer 17

visceral piston

concussive limb impact transmitted to the thorax

lumbosacral flexion pressurizing abdominal cavity

Question 18

the oxygen pressure in thoroughbreds is around what?

Answer 18

68mmHg

Question 19

what is the main cause of exercise hypoxemia?

Answer 19

diffusion limitation! the blood doesn’t have time to become fully oxygenated because the blood is moving so quickly

Question 20

how do horses deal with high CO2 levels in the blood?

Answer 20

they have a good buffering system to manage the high CO2 levels

Question 21

why doesn’t training help with hypoxemia?

Answer 21

Because the heart is now bigger and can pump more volumes of blood more efficiently, and if the blood is pumping faster it has no time to become saturated with oxygen in pulmonary capillaries

Question 22

what is exercise-induced pulmonary hemorrhage?

Answer 22

when there is bleeding from the lungs during exercise usually paired with poor athletic performance

Question 23

what causes the lungs to bleed during exercise?

Answer 23

There is a rupture in the alveolar capillary membranes and there is a leakage of blood into the alveolar spaces. In the pulmonary artery, there is such a high pressure, and in the alveoli there is a lot of negative pressure (vacuum), creating a huge pressure difference so the capillary wall breaks and blood can then get into the lungs