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

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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).

http://www.youtube.com/watch?v=_b0AZmmLgi0&feature=related

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 lungs.

Locomotory respiratory couplingInhalation – thoracic unloading phase

Exhalation – thoracic loading phase

• A – inhalation• B - exhalation

The responses of the respiratory system to training

• 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 rate.

• 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

breathing.

Responses to training

• Training increases maximal oxygen uptake (VO2max) due to an increase in cardiac output / efficiency of O2 extraction from the air breathed.

• 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 workload.

• 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

capacity.• Where no gas exchange occurs its called anatomical dead space.

• 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 & expiration.

• 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

1. What is the normal rate of breathing in an average adult horse at rest?

2. How high can the breathing rate go during strenuous exercise?3. Why does the breathing need to increase during exercise?4. Describe the relationship between breathing rate and stride in

canter & gallop.5. What is the overall aim of training in relation to the respiratory

system?6. What is alveolar recruitment?7. How does muscular development with training aid the adaptation

of the respiratory system?8. What is Vo2 max.?