Limits to exercise tolerance 3 Flashcards
How does a nasoesophageal catheter work work?
It goes up the nose, down the throat and into the stomach where there is two pressure transducers, one in the stomach and one in the oesophagus. WHen diaphragm contracts it moves down which increases stomach pressure and decreases esophageal pressure
What is the respiratory metaboreflex?
When respiratory muscles become fatigued, it sends a signal that changes blood flow to other muscles
What is observed regarding leg blood flow when work of breathing is increased?
It decreases
When using a nasoesophageal catheter, where are the pressure transducers?
Stomach and oesophagus
What is observed regarding leg VO2 when work of breathing is increased?
It decreases
How efficient is muscle O2 extraction?
Very
Why is muscle oxygen extraction unlikely to limit VO2max?
At high intensity exercise the difference in oxygen conc between the artery entering the muscle and the vein leaving the muscle is high meaning it is very efficient
What explains most of the variance in VO2max between people?
Cardiac output
What explains the early increase in VO2max with exercise training?
Plasma volume
What is observed in the blood in the first week after beginning training?
Rapid increase in plasma volume
How to artificially increase plasma volume?
Dextran infusion
What is observed in the VO2max of people who have had their blood plasma volume artificially increased as a result of a dextran infusion?
An increase of ~4%
How does dehydration affect performance?
It leads to a lower plasma volume which leads to lower blood flow and stroke volume
In most people, what is the correlation between VO2max and performance time in a a marathon?
High
In elite athletes, what is the correlation between VO2max and performance?
Not as strong as in the general population
Why may the VO2max of elite athletes not perfectly correlate to performance?
other factors such as mechanical efficiency, running economy etc
Which test could be better than VO2max for elite athetes?
Lactate threshold
What was observed regarding time to fatigue differences at 70%VO2max in low, mixed and high CHO diets?
The low CHO diet performed the worst with around 1 hr, the high performed the best between 2 and 5 hrs
Correlation between CHO content in diet and muscle glycogen levels?
Higher CHO content in diet means a higher muscle glycogen content
What was observed when looking at the time when muscle glycogen depletion occurs in placebo and CHO-fed groups during exercise?
They reach muscle glycogen depletion at the same time (3hrs)
Why could CHO-fed people exercise for longer than placebo despite reaching muscle glycogen depletion at the same time?
Taking on more CHO means it no longer becomes a reason for fatigue
What role can muscle glycogen have other than a fuel?
A signalling molecule
Subsarcolemmal region meaning?
Below the sarcolema
Which type of muscle glycogen storage is most closely associated with fatigue?
Intramyofibrillar
How does a lack of muscle glycogen affect calcium?
It affects its release rate
Which out of glycogen, glucose, FAs can generate ATP the fastest?
Glycogen
What is McArdles disease?
Lack of enzymes required to break down muscle glycogen
Which fuel is more efficient, carbs or fats?
Carbs
