respiratory control and responses to exercise
TRANSCRIPT
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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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Mechanism forVentilatoryEquivalent for Oxygen (VE/VO2)
Electron Transport Chain
O2
H+ (Hydrogen)
Krebs
Cycle
PATHW
AY BLO
CKE
D
X
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Mechanism forVentilatoryEquivalent for Oxygen (VE/VO2)
Formation of Lactic Acid
Pyruvic Acid + 2H Lactic Acid
So nowwhat happens to the lactic acid?
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Mechanism forVentilatoryEquivalent for Oxygen (VE/VO2)
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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Fuel Use - Respiratory ExchangeRatio (RER)
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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Fuel Use - Respiratory ExchangeRatio (RER)
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.