Physiological response to training - respiratory

Physiological effects of training
The respiratory system
Cast of
equine lung
(A) Trachea
B) Cartilage
C) Vocal cord
D) Epiglottis
1) Buccal cavity 2) Nasal Cavity (open to pharynx) 3) Inferior maxillary sinus 4)
Superior maxillary sinus 5) Frontal sinuses 6) Guttural pouch 7) Pharynx
8) Trachea 9) Bronchus 10) Alveolus 11) Lungs 12) Larynx
Respiratory System revision
Primary function – gas exchange.
Provides O2 to tissues & removes CO2.
Resting respiratory rate = 8-16 breaths / minute.
During intense exercise this can increase up to
35 x normal rate.
• Respiratory system is a limiting factor for
maximal performance.
Anatomy affecting performance
• Larynx – regulates airflow into trachea.
• Laryngeal displacement (swallowing the
tongue) can affect performance.
• Whistlers / roarers can not open left vocal
chord effectively due to nerve degeneration.
• Surgical procedures are an option if
performance is compromised (hobdays,
tiebacks, tubing).
Locomotory-respiratory coupling
• In canter & gallop, stride matches breath 1:1.
• Each phase of the stride corresponds to each phase of
respiratory cycle.
• Piston-pendulum effect.
• Inspiration – horses raises neck & forelegs ,guts move
back allowing diaphragm to move back.
• As scapula moves forward, serratus ventralis pulls ribs
up & open.
• When forelimb lands (deceleration phase), gust move
forwards & push on diaphragm, making air leave the
Locomotory respiratory coupling
Inhalation – thoracic
unloading phase
Exhalation – thoracic loading
• A – inhalation
• B - exhalation
The responses of the respiratory system to
• During exercise the respiratory rate can increase to 120bpm
to cope with oxygen demand.
• At canter & gallop, the respiratory rate is locked to the stride
• Training can increase ability to supply & utilise oxygen.
• Training clears the alveoli of mucous, increasing the functional
capacity of the lungs.
• Known as alveolar recruitment.
• The capillaries surrounding these alveoli proliferate.
• Leads to greater surface area for increased gaseous exchange.
• Chest / diaphragm muscles development aids efficient
Responses to training
• Training increases maximal oxygen uptake
(VO2max) due to an increase in cardiac output /
efficiency of O2 extraction from the air
• Recovery rate of respiration after exercise
improves with training.
Increase O2 intake
With exercise the respiratory/ventilation rate changes.
Can increase to 120 bpm in faster paces with max being 180 bpm.
At canter & gallop, the respiratory rate is locked to the stride rate.
Exercise increases depth of breathing.
Average horse lung holds 4-7 litres of air – exercise can raise this capacity
to 10 litres.
• Rate of diffusion of the alveoli increases due to greater demand for O2 by
the tissues.
• Maximal rate of O2 is called VO2max.
• Occurs when O2 upload does not increase any further despite increase
• When workload is greater than provided by VO2max horses demand
exceeds aerobic capacity & horse has to provide energy anaerobically.
Alveolar Recruitment
• Resting horse does not need to use entire air space or lung
• Where no gas exchange occurs its called anatomical dead
• Alveoli that are not perfused with blood are called alveoli
dead space.
• At rest dead space accounts for 70% of the tidal volume &
30% of the alveolar volume.
• More alveoli are required as work intensity increases.
• Training stimulates debris collected in alveoli of resting
horses to be removed & alveoli are ‘recruited’.
Pulmonary Capillarisation
• Training causes increase in No. of capillaries
surrounding alveoli.
• Results in greater proportion of oxygen
breathed in being transported to the muscles.
Gaseous exchange
Proportion of O2 breathe din being transported to muscles.
Muscular Development
• Diaphragm &
skeletal muscles
associated with
inspiration &
exhalation undergo
hypertrophy in
response to training.
• This results in
increased efficiency
of inspiration &
The technique we use to measure respiratory mechanics requires the determination of the intrathoracic
pressure and the flow of air in and out the respiratory system. A tube positioned in the esophagus (similar
to nasogastric tubes used to administer mineral oil in a horse with colic for example) measures the
pressure within the thorax; at the end of tube, a measuring device called pressure transducer is placed.
The tube is small and its placement is well tolerated by horses. A device call a "pneumotacograph" placed
on a facial mask measures the flow of air.
These two signals, allow the calculation of various respiratory parameters such as tidal volume (quantity of
air inspired during a breath), minute ventilation (volume of air inhaled per minute), airway resistance (the
resistance offered by the respiratory tract preventing the movement of air; horses with COPD have an
obstruction of the airway which impairs airflow), airway compliance (measures the elasticity of the lung;
also abnormal in horses with COPD), inertance. The calculation of inertance provide information on the
elasticity of the lung.
Revision - respiratory
What is the normal rate of breathing in an average adult horse at
How high can the breathing rate go during strenuous exercise?
Why does the breathing need to increase during exercise?
Describe the relationship between breathing rate and stride in
canter & gallop.
What is the overall aim of training in relation to the respiratory
What is alveolar recruitment?
How does muscular development with training aid the adaptation
of the respiratory system?
What is Vo2 max.?

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