Exercise Physiology Flashcards
Explain the effects of exercise and training on the equine respiratory system
Aim is to have more oxygen in an to rid of the excess CO2
Increased respiratory rate and tidal volume
At walk, trot, & slow canter horses increase their breathing rate
At slow/medium canter horses increase their breathing rate and depth of breathing
At gallop horses increase their depth of breathing only
Hypoxaemia (pa02 is 60mmHg -horse gets close to this)
Hypercapnia
This is down to a number of factors:
-piston pendulum theory
-Blood gas membrane
-Speed= stride length x stride frequency (stride length typically increase for possibly deeper breathing)
-Significant shortening of the transit time for blood in pulmonary capillaries as CO increases)
Measuring:
Oxygen uptake V02 during exercise using breath by breath or open flow approaches
Explain the effects of exercise and training on the cardiovascular system
Aim is to increase blood flow to the limbs
1) Increase cardiac output (product of heart rate & stroke volume)
2) Increase oxygen carried in blood (more O2 or red blood cell (blood doping/ high altitude>2weeks)s;
3) Redistribute blood flow (i.e. to muscles needing it [not GIT])
Outline how increasing cardiac output assist equine exercising
Increase size of heart (Concentric hypertrophy)
-typically athletic horses will have larger heart masses due to this
Q = cardiac output (HR x stroke volume)
Systolic blood pressure shouldn’t alter during exercise as the cardiovascular system will counter the increase CO
Describe the importance of the spleen and changes in packed cell volume in oxygen delivery during exercise in the horse
Increasing Oxygen Carried in the Blood
-Release of red blood cells from the spleen increases oxygen carriage (but also viscosity)
-Spleen as proportion body weight – high in horse
(variation within species - The more athletic the animal the better it is at releasing splenic Hb)
Explain what blood doping is
Drugs developed to treat anaemia in people (e.g. with renal disease)
Erythropoietin (EPO)
-Recombinant human EPO
-‘Natural’ nutraceutical
Stimulates production of RBCs
‘oxygen in a pill’
Drug that inhibits hypoxia-inducible factor (HIF) prolyl hydroxylase
HIF is a positive regulatory protein for EPO gene expression
At high [O2], HIF prolyl hydroxylase targets HIF for destruction
Because of inhibition of prolyl hydroxylase, HIF isn’t broken down, thus the RBC production continues even when the body isn’t starved of oxygen
Erythrocythaemia – consequences?
List disorders of the equine respiratory system which limit performance
Resistance to airflow in the nasal cavity
Laryngeal Hemiplegia
Dorsal Displacement of Soft Palate (DDSP)
Recurrent Airway Obstruction (RAO)
Exercise-Induced Pulmonary Haemorrhage (EIPH)
Explain how performance can be limited by resistance to airflow
Equine species are obligate nose breathers
Meaning pulmonary resistance more than doubles during heavy exercise despite nares dilation, full laryngeal abduction and bronchodilation
In circumstances of pulmonary diseases such as asthma, COPD air resistance is further increase due to reduced diameter of conducting airways
Explain how performance can be limited by laryngeal hemiplagia
Partial paralysis of larynx
Inadequate gas exchange
Surgical treatment
Hence importance of pre-sale endoscopic examinations
Lead to ‘roaring’
95% of time left hand side – unsure why
Explain how performance can be limited by dorsal displacement of soft palate (DDSP)
Choking down” “gurgling”
Loud, expiratory gurgling noise in ~2/3rd of cases
Diagnosis by endoscopy and nasal occlusion
Severely reduces VO2max….
Explain how performance can be limited by recurrent airway obstruction (RAO)
Such as COPD (lower airway inflammation) from environmental factors, hyper-responsiveness, bacteria, mycoplasma, parasites, viruses, and allergies
Explain how performance can be limited by Exercise induced pulmonary haemorrhage (EIPH)
Haemorrhage into the airways that occurs in horses that are exercising at high intensity
How is EIPH identified?
Blood present in airways after exercise
How is EIPH diagnosed?
Based on post-exercise endoscopy
Typically treated with furosemide, ‘Lasix’ but is illegal in UK
List systemic disorders of the equine respiratory system which limit performance
Bacterial Infection (more common than viral)
Equine Influenza
(LRT affected more than LRT by diseases)
Explain how performance can be limited by equine influenza
Destruction of ciliated epithelium disrupts mucociliary elevator
Leads to ulcerations it RT reducing diameter
Build up of mucus which horse has to cough to remove
List external factors which limit equine performance
Incline
Ground conditions
Thermal environment
Rider to horse weight
Heat
Explain how performance can be limited by incline
~12% increase in workload per 1% increase in gradient
