Physiology of endurance events

Question 1

define the term performance vO2

Answer 1

the O2 consumption which can be maintained for a given period of time

the percentage of VO2 max which an athlete can run at

level of aerobic metabolism which can be maintained

Question 2

explain the concept of performance O2 deficit

Answer 2

the difference between the amount of energy required at the start of a race and the amount of energy which can be provided by aerobic metabolism

develops because aerobic metabolism is slow to switch on, so doesn’t meet race demands at the start

Question 3

explain the concept of efficiency in relation to endurance running

Answer 3

= the oxygen cost of generating a given running speed/power output

so interacts with performance VO2 to determine the speed at which the athlete can run at

lower economy/ efficiency is better!!!

Question 4

explain why the respiratory system could be considered to be a limiting factor of VO2 max when carrying out maximal exercise

Answer 4

at these intensities, elite athletes have been shown to undergo arterial desaturisation due to high cardiac output = reduced red cell transit time in the lungs

Question 5

what is the Fick equation for VO2

Answer 5

VO2 = Q x (a-v O2 difference)

Q = cardiac output

Question 6

why is cardiac output considered to be the main factor which limits VO2max

Answer 6

because the muscle’s capacity for blood flow far exceeds the hearts capacity to pump blood

Question 7

describe the study which demonstrates that CO is the limiting factor of VO2 max

Answer 7

isolated the quads and measured the change in blood flow with exercise

3kg of muscle had a blood flow of 6-7l/min

normalised this gives 200ml/kg/min of muscle blood flow

whole body exercise e.g running uses around 30kg of muscle which would require around 60l/min of blood

heart could never produce this, max around 5l

Question 8

why are metabolic processes not considered to be limiting factors of VO2 max

Answer 8

flux of pyruvate which is possible, through pyruvate dehydrogenase is sufficient to meet demands of the muscle

Question 9

how does physical training lead to gains in VO2 max?

Answer 9

increases CO

increases rate of O2 extraction from the blood

Question 10

explain the benefit of having a better running economy in two different ways

Answer 10

1) for a given speed, use less VO2 and therefore less energy
2) for a given VO2, can run at a faster speed

Question 11

give two reasons why a better running economy may lead to an increased time to fatigue

Answer 11

1) less energy required to run at a given speed therefore slower depleation of glycogen
2) less heat production for a given running speed therefore less thermal stress on the body

Question 12

define the following:
gross efficiency

net efficiency

work efficiency

delta efficiency

Answer 12

all energy expenditure including that at rest

energy expenditure - expenditure at rest

energy expenditure - rest and expenditure linked to unload pedaling

change in energy expenditure when changing work rate

Question 13

which muscle fibre type is more efficient and explain the evidence which shows this

Answer 13

type 1

athletes with a higher percentage of type 1 fibres had similar performance VO2 to those with more type 2 but had a higher performance power output

i.e higher power output for similar VO2

Question 14

can running economy be improved with training and what evidence is available to show this

Answer 14

yes can get slight improvements over long periods of time

Paula Radcliff showed a decrease in the VO2 when running at a set speed over a period of 5 years without a change in her VO2 max

Question 15

explain the current theory regarding whether or not a <2hr marathon is possible

Answer 15

yes
models suggest that a runner with a good VO2 max, who can run at a high % of this and had exceptional economy can do it

but would need exceptional values in all 3

is rare to find exceptional VO2 max and economy in the same person

Question 16

what is the most important factor for determining performance in endurance events

cite evidence from comparison between marathon runners and long distance runners which supports this

Answer 16

running economy

marathon runners have lower VO2 max but better running economy vs long distance runners

Question 17

compare the variables contributing to endurance performance in erterian vs spanish runners and explain why erterian runners perform better in marathons

Answer 17

spanish have a better VO2max and can run at a higher percentage of their VO2 max therefore can run at a faster speed when running at LT

however, at 21km/h whcih is world record pace erterian have a much better running economy