Exercise Phy. week 7

winniesmith2's version from 2018-01-10 19:02

Section 1

Question Answer
Mechanisms of respiratory regulations• Central chemoreceptors and Peripheral chemoreceptors .
Central chemoreceptorsStimulated by CO2 ↑ in cerebrospinal fluid  Rate and depth of breathing ↑  remove excess CO2 from body
Peripheral chemoreceptorsIn aortic bodies (where all the blood goes through) carotid bodies (all the blood that goes through is to the brain) – Sensitive to blood PO2, PCO2, H+ . These receptors ALONE protect the organism against reduced oxygen pressure in inspired air!
the increased ventilatory drive at altitude is due to Ventilation is increased when PO2 ↓. . Driven by less oxygen in the air
Regulation of pulmonary ventilation• Body must maintain homeostatic balance between blood PO2, PCO2, and pH • Requires coordination between respiratory and cardiovascular systems. Coordination occurs via involuntary regulation of pulmonary ventilation.
Ventilation and acid-base balancePulmonary ventilation removes H+ from blood. (Muscle) H+ + HCO3- (bicarbonate, main buffer) <--> Carbonic acid (H2CO3) <--> CO2 + H20 (lung). The more heavily i breath the less protons that can be found in the system.
Increased ventilation helps to maintain a stable pH Increased ventilation helps to maintain a stable pH • H+ is buffered by bicarbonate: H+ + HCO3 -  CO2 + H2O • “Excess CO2“ stimulates central and peripheral chemoreceptors -> ventilation increases. – Increased ventilation results in CO2 exhalation • Reduces blood PCO2 and H+ concentration (pH increase). – Decreased ventilation results in build-up of CO2 • Increases blood PCO2 and H+ concentration (pH decrease).
What is ventilatory thresholds Point during exercise when ventilation increases disproportionately to oxygen consumption. Break point is not driven by getting more oxygen, it is driven by getting rid of C02.
Aerobic ventilatory threshold: Excess CO2Determination of the aerobic ventilatory threshold using the V slope method
Ventilatory equivalent for oxygen• The ratio between ventilation (VE) and VO2 • Example: VE = 80 L/min; VO2 = 2.0 L/min  Ventilatory equivalent for oxygen (VE/VO2)= 40.0
If ܄VE = 60 L/min; ܄VO2 = 1.6 L/min and V CO2= 1.7 L/min, the ventilatory equivalent for O2 and CO2 are:B. 37.5 and 35.3
Ventilatory equivalent for oxygen and the aerobic ventilatory thresholdVE/VO2 remains relatively constant over a wide range of submaximal exercise levels and starts to increase at the aerobic ventilatory threshold (reason: oxygen demand keeps increasing linearly, whilst there is a break point in VE)- has a break point to get CO2 out of system
Lactate threshold – ventilatory threshold. The aerobic ventilatory threshold is found at approximately the same intensity lactate begins to accumulate in the blood (=lactate threshold) – WHY?B. Hydrogen ions are formed and buffered, the resulting CO2 needs to be blown off

Section 2

Question Answer
The respiratory compensation point• Recap maximal lactate steady state (MLSS): Highest intensity at which lactate production = lactate removal -> at higher intensities, progressive lactate accumulation and enhanced CO2 production (H+ + HCO3 - -> CO2 + H2O)  ventilation further increased ->second break point in ventilation curve: Respiratory compensation point.
Determining the respiratory compensation point- Up to RCP, ventilation increases linearly with CO2 - After RCP, “less efficient” ventilation (less CO2 exhaled per litre of ventilated air)
two thresholds, many names; aerobic ventilatory threshold – Ventilatory threshold – Aerobic threshold – Aerobic gas exchange threshold – Ventilatory threshold 1
two thresholds, many names; respiratory compensation point – Anaerobic ventilatory threshold – Anaerobic gas exchange threshold – Ventilatory threshold 2
The respiratory compensation point (RCP)…C. …occurs at a similar intensity as the lactate turnpoint
overview page 4
training zones with typical values can keep going above intensity of VT and RCP but have to go at intervals . page 4
key paper faude et al 2009, page 4
Practicalities of ventilatory thresholds for training prescriptionadavn; no blood sampling. disad; mask needed, expensive equipment,
Effects of training on ventilatory thresholds• “The better trained, the higher the threshold” – absolute VO2 in L/min ↑ – %VO2max at which threshold occurs ↑. ex. page 5
Ventilatory thresholds to track performance• Similar to blood lactate thresholds, better predictors of performance than VO2max VO2max may remain constant, whereas aerobic ventilatory threshold and RCP increase during season: • by 8% (VT) and 6% (RCP) in world class cyclists • by 10% (VT) in top-class endurance runners

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