Respiratory responses to exercise

How do central chemoreceptors work?

• Stimulated by increase in CO2 in the cerebrospinal fluid

• This will cause an increase in depth and rate of breathing, and remove excess CO2 out of the body

How do the 2 peripheral chemoreceptors work?

Carotid bodies = found in the neck, detecting levels of O2, CO2, H+ going to the brain

Aortic bodies = found in the heart, detecting levels of O2, CO2, H+ going to the heart

What happens to ventilation as altitude increases?

• As altitude increases the partial pressure of oxygen decreases

• Therefore ventilation rates increase in order to maintain homeostasis

• This coordination occurs via involuntary regulation and pulmonary regulation

How does increased breathing rate remove more CO2?

• Intense exercise will produce lactate and protons due to anaerobic work

• Bicarbonate buffer will combine with these protons to form carbonic acid

• Carbonic acid then travels into the blood, and falls apart into CO"2 and water

• CO2 will be removed as breathing occurs

What is ventilatory threshold?

• The point where minute ventilation increases disproportionately to oxygen consumption (i.e. breathings increases faster than VO2 uptake)

What is VT1?

Ventilatory threshold 1 signals the shift from fat to carb fuel usage

What is VT2?

Ventilatory threshold 2 signals the transition to unsustainable high intensity exercise

What is ventilatory equivalent for oxygen?

The amount of ventilation needed to take in 1 litre of oxygen

e.g. ventilation of 80L and VO2 of 2L, means ventilatory equivalent is 40L

What causes the ventilatory equivalent for oxygen to increase at VT1?

• As intensity increases the blood H+ increases, producing more CO2

• The increased CO2 causes ventilatory responses (e.g. increased breathing rate) to remove it

• Therefore ventilation increases to reduce blood CO2 rates

What is the respiratory compensation point (RCP)?

• After MLSS CO2 and lactate levels will increase, causing ventilation to further increase

• This steeper rise is called the RCP, and is at the same point as VT2

What other factors cause increased ventilation?

• Increased core temperature

• Increased potassium levels

• Mechanical receptors in muscles

What are the typical values with different training zones?

What are the advantage for finding a persons ventilatory threshold?

• Can help to prescribe training plans

• Not invasive (e.g. don’t have to prick and remove blood from athlete)

What are the disadvantages for finding a persons ventilatory threshold?

• Equipment is more expensive than other methods, such as blood lactate test

• Face and nose mask can still be uncomfortable, and cause hyperventilation

What are the effects of training on the VT1 and VT2 of an athletes VO2 Max

• Endurance training increases VT1 and VT2 as a percentage of VO₂max, allowing athletes to exercise at higher intensities before lactate accumulation and respiratory compensation occur,

• VO₂max remains relatively unchanged.