Limits to exercise tolerance 1 Flashcards
What is fatigue?
The inability to maintain power output or force during repeated muscle contractions
Which test could be done to assess exercise performance?
VO2max or VO2peak
Which test could be done to assess exercise capacity?
Time to exhaustion
What are the three exercise intensity domains?
Moderate, heavy, severe
What level of exertion is moderate?
Anything below lactate threshold/gaseous exchange threshold
When is lactate threshold reached?
When the production of lactate is occuring at a faster rate to the removal rate
What intensity of exercise is heavy?
Between lactate threshold and critical power/critical speed
What intensity exercise is severe?
Anything above critical power/critical speed
How is critical power tested?
VO2max test, record highest power output (wattage) from that. Then have them do several time to exhaustion tests with the resistance of the bike being different %s (500, 100, 50 etc) of their VO2max test. Measure the time they can go until exhausiton against these different %s. Can plot a curve which will flatten (after going down). Flattened curve is intensity that the person can maintain for a long period of time
What are the likely fatigue mechanisms for moderate exercise?
Hyperthermia, mental fatigue and muscle damage
What are the likely fatigue mechanisms for heavy exercise?
Glycogen depletion and hyperthermia
What are the likely fatigue mechanisms for severe exercise?
Depletion of finite energy stores (W’)
Which three elements dictate performance velocity or power?
Performance VO2, Performance O2 deficit, Gross mechanical efficiency
What can limit performance VO2?
Lactate threshold, muscle capillary density
What can limit lactate threshold directly?
Maximal oxygen consumption, aerobic enzyme activity, distribution of power output
What can limit maximal oxygen consumption directly?
Muscle capillary density, stroke volume, max heart rate, hemoglobin content
What directly influences performance O2 deficit?
Total buffering capacity and distribution of power output
What is total buffering capacity?
How good our muscles are at buffering acidosis
What is acidosis?
Acid build up in the muscles as a result of exercise
What can affect performance O2 deficit and performance VO2?
Distribution of power output
How can total buffering capacity be changed?
Training status and nutrition
Which compound can improve total buffering capacity during exercise?
Sodium bicarbonate
Why can taking sodium bicarbonate help with high intensity exercise?
It can help with buffering of acidosis
What can influence gross mechanical efficiency?
% slow twitch (type I) muscle fibres, anthropometry and elasticity
Which type of muscle fibre is more efficient?
Slow twitch (type I)
If two athletes were the same height but one had longer legs, which one would be more efficient?
One with longer legs
Is it better to have stiffer or more relaxed tendons?
Stiffer as energy can be transferred more efficiently
Which type of athlete has the highest VO2max?
Endurance
What sports do “endurance athletes do?
Cross country skiing, running
Why do cross country skiers have a higher VO2 max than marathon runners?
They use both their arms and their legs
Highest every VO2max?
93-95mL/kg/min
Which type of marathon does VO2max correlate best with?
It correlated with normal marathon better than ultra marathon
Why does VO2max correlate better with a normal marathon than an ultramarathon?
Ultramarathons have a slower pace and so are less reliant on VO2 for performance
How does VO2max correlate with health/age?
It declines as you get older
What age related issues can VO2max be used to predict?
Mortality and post surgery outcomes
What is the Fick equation?
VO2 = Q (a-v O2diff)
Q is cardiac output
a-v O2diff is the muscle O2 extraction
How is cardiac output measured?
Stroke volume * heart rate
What is a-v O2diff in the fick equation?
The amount of oxygen in the artery going to the muscle minus the amount of oxygen in the vein leaving the muscle–> bigger means muscle is extracting more O2 from the blood
In what ways can the a-v O2diff be limited?
Either a limitation in the limitation in the delivery of the oxygen to the muscle, or a limitation in the muscle itself and its ability to extract oxygen
How is muscle VO2 measured?
Catheters are inserted into different blood vessels in the body.
What are the main key steps in O2 transport?
Lungs, respiratory muscles, heart, muscle, mitochondria
