Respiratory Control and Responses to Exercise

8/3/2019 Respiratory Control and Responses to Exercise

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Respiratory Control and Responses toExercise

SR1018 Scientific

Principles


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Aims of the Session

To identify responses of the respiratory system

to acute exercise.


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Respiratory

Regulation


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Ventilatory Response to Exercise

Two Stage

Response


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Minute Ventilation (VE)

VE = Breathing rate x Tidal Volume

e.g. 12 breaths/min x 0.5L

= 6.0L/min-1

In our practical we collect air samples for 1

minute, so bag volume = VE


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Minute Ventilation (VE)

QUESTION:

Two identical people have an identical VE.

Does the same amount ofoxygen necessarilyreach their lungs?


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VE

, AlveolarVentilation & AcuteExercise

Volume inspired per breath = 500ml

Breaths per minute = 10

Dead space=

150ml

Minute volume (VE) = volume/breath x breaths/minute

= 500ml x 10

= 5 L/min

TASK: HOW MUCH AIR WILL REACH THE ALVEOLI?

Alveolar ventilation = (inspired vol dead space) x breaths/min

= 350ml x 10

=3.5L/min


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VE

, AlveolarVentilation & AcuteExercise

Volume inspired per breath = 1000ml

Breaths per minute = 5

Dead space=

150ml

Minute volume (VE) = volume/breath x breaths/minute

= 1000ml x 5

= 5 L/min

TASK: HOW MUCH AIR WILL REACH THE ALVEOLI?

Alveolar ventilation = (inspired vol dead space) x breaths/min

= 850ml x 5

=

4.25L/min


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VE & Acute Exercise

Low intensities tidal volume.

Higher intensities breathing frequency


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VE & VO2 During Exercise

You could plot

a similar

graph, e.g:

VO2 on the x

axis.

VE (bagvolume) on the

y axis.

55 70%of

VO2max


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Ventilatory Break Point/Threshold

Disproportionate increase in VE with increased

exercise intensity.


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Ventilatory Equivalent for Oxygen

Volume of air ventilated (VE)

Volume ofO2 used (VO2)

Rest = 20 25L of air per L ofO2

Strenuous = 30 40L of air per L ofO2

Activity


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Ventilatory Equivalent for Oxygen(VE/VO2)

TASK: Calculate The ventilatory equivalents for thefollowing exercise intensities

VEL.min VO2L.min VE/VO2

35 1.5

48 2.0

62 2.5

90 3.0

23.3

24

24.8

30.0


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Ventilatory Equivalent for Oxygen(VE/VO2)

You could

calculate VE/VO2from your

practical results


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Mechanism forVentilatoryEquivalent for Oxygen (VE/VO2)

CO2 production:

Metabolic CO2C

6H12O6+O2p CO2 +H2O+ 38ATP

Extra non-metabolic CO2 is also producedthrough lactate buffering.

This causes the disproportionate rise in VE


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Electron Transport Chain

O2

H+ (Hydrogen)

Krebs

Cycle

PATHW

AY BLO

CKE

D

X


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Formation of Lactic Acid

Pyruvic Acid + 2H Lactic Acid

So nowwhat happens to the lactic acid?


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Buffering of Lactic Acid

Lactic acid +NaHCO3 Na Lactate +H2CO3

H2CO3 H2O+ CO2


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Exercise Intensity and BloodLactate Accumulation

Ventilation (VE)


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Fuel Use - Respiratory ExchangeRatio (RER)

C6H12O6+ O2p CO2 + H2O + 38ATP

C6H12O6+ 6O2p 6CO2 + 6H2O + 38ATP

RER = VCO2/VO2 RER = 6CO

2

/6O2

= 1.0 38 molecules of ATP produced/6 molecules ofO2 are required.

38/6 = 6.3 molecules of ATP produced for every molecule ofO2


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C16H32O2 + O2 p CO2 + H2O + 129ATP

C16H32O2 + 23O2 p 16CO2 + 16H2O + 129ATP

RER = VCO2/VO2 RER = 16CO

2

/23O2

= 0.7 129 molecules of ATP are pr oduced/23 molecules of O2

required.

129/23 = 5.6 molecules of ATP produced for every molecule ofO2


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0.7 = 100% fat.

0.85 = 50% fat, 50% CHO. 1.00 = 100% CHO.


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Recovery and Blood Lactate Levels


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Respiratory Limitations to PerformanceRespiratory muscles may use more than 15% of totaloxygen consumed during heavy exercise and seem to bemore resistant to fatigue during long-term activity thanmuscles of the extremities.

Pulmonary ventilation is usually not a limiting factor forperformance, even during maximal effort, though it canlimit performance in highly trained people.

Airway resistance and gas diffusion usually do not limit

performance in normal healthy individuals, but abnormalorobstructive respiratory disorders can limit performance.


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Key Points

The respiratory centers in the brain stemset the rate and depth of breathing.

Chemoreceptors respond to increases in

CO

2 andH+

concentrati

ons

or todecreases in blood oxygen levels by

increasing respiration.

Pulmonary Ventilation

(continued)

Ventilation increases upon exercise due toinspiratory stimulation from muscle activity

which causes an increase in muscletemperature and chemical changes in thearterial blood (which further increaseventilation).


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Key Points

Breathing problems associated withexercise include dyspnea, hyperventilation,and the Valsalva maneuver.

During mild, steady-state exercise,ventilation parallels oxygen uptake.

PulmonaryV

entilation

The ventilatory breakpoint is the point atwhich ventilation increases though oxygenconsumption does not.

Anaerobic threshold is identified as thepoint at which VE/VO2 shows a suddenincrease, while VE/VCO2 stays stable. Itgenerally reflects lactate threshold.

. .. .


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Recommended Reading

Baechle, T. R., Earle, R.W. (eds) (2000) Essentials ofstrengthtrainingandconditioning. 2nd ed., National

Strength and Conditioning Association. Champaign, Ill.:Human Kinetics.

Marieb, E.N. (2000) Essentials ofhumananatomyandphysiology. 6th ed., Addison Wesley, Longman.

McArdle, W.D., Katch, F.I., Katch, V.L. (2006)

Essentials ofexercise physiology. 3rd

ed., London:Lippincott, Williams & Wilkins.

Wilmore, J.H. & Costill, D.L. (2004) Physiologyofsportandexercise. 3rd ed., Champaign, Ill.:Human Kinetics.

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Respiratory Control and Responses to Exercise