Limits to exercise tolerance 2 actually Flashcards
Arguments against lungs being a limiting factor in VO2max?
Alveolar area is v large, ventilation increases more than oxygen uptake, pp of oxygen in alveoli and arteries is maintained at VO2max
Arguments in favour of lungs being a limiting factor in VO2max?
At normoxia, the oxygen saturation of haemoglobin declines as the intensity of exercise does, hypoventilation, mechanical constraints
What is hyperoxia?
Atmospheric oxygen partial pressure is higher than usual
What is normoxia?
Atmospheric oxygen partial pressure is the same as usual
What is hypoxia?
Atmospheric oxygen partial pressure is lower than usual
What is hypoventilation?
breathing that is too shallow
How can hypoventilation be a limitation of VO2max?
Someone may have the capacity for a certain oxygen uptake but arent sensitive enough to the stimuli (exercise) to increase the ventilation rate
What are the axis of a flow volume loop?
Flow rate in L/s on Y axis, volume in L on the x axis
How to create a flow volume loop?
Maximal inspiration then forcefully expire all air in lungs as quickly and as hard as possible
How can we test whether lung function is a limiting factor of VO2?
Changing density of inspired air
What was observed as a result of changing the density of inspired air to see whether lungs are limiting or not?
Less dense air overcomes the limitation of lungs reaching expiring capacity
What is pulmonary oedema?
Swelling in the lungs
How does pulmonary oedema negatively affect gas exchange in the lungs?
The swelling causes the interstitial space between the alveoli and capillary to increase thus gas exchange takes longer
How can alveolar capillary diffusion limit VO2max?
Only one RBC can pass through a capillary at a time. In untrained this is 0.4-0.5s whereas in trained it is <0.4. Longer means more time to take oxygen to blood so lower VO2max
Are lungs a limiting VO2max factor in untrained individuals?
Not a huge amount of evidence to support it
Are lungs a limiting VO2max factor in trained individuals?
Some evidence that this may be true
What is hyperpnea?
Increased ventilation
What is the cost of exercise hyperpnea?
Respiratory muscles have a power output of around 50 watts
WHat is unique about respiratory muscles?
They can produce a lot of force relative to their size
What is proportional assisted ventlation?
Participant begins inhaling–> rest of air is forced into lungs via machine
What is RPE?
Rating of perceived exertion
What happens to leg RPE in unloaded (proportional assisted ventilation) condition?
It is a lot lower than load or control
How to load inhalation?
Have the participant lift a small weight when they breathe in–> lungs and respiratory muscles have to work harder
What is an MIP?
Maximum inspiratory mouth pressure test
