Biochemistry of the Middle Distance Athlete

Question 1

What is the critical power concept?

Answer 1

That every individual has a different power-duration relationship that produces a different hyperbolic curve and a distinct critical power.

Question 2

In an endurance type athlete what type of expression do they have of muscle fibres compared to a sprint type athlete?

Answer 2

Low type 2

Question 3

Which type of athlete, endurance or sprint, has a better developed anaerobic energy provision pathway?

Answer 3

Sprint

Question 4

Which type of athlete, endurance or sprint, has a higher critical power asymptote?

Answer 4

Endurance

Question 5

What does the critical power asymptote denote?

Answer 5

The upper limit for the attainment of steady state.

Question 6

What is the length of a middle distance sporting event?

Answer 6

~2-30 minutes

Question 7

What is the power-duration relationship equation?

Answer 7

W’ = Tlim x (W-CP)

Question 8

What two parameters does the power duration relationship equation describe the tolerable duration of a constant power output in?

Answer 8

The capacity of anaerobic systems reflected by W’ and the upper limit for wholly aerobic energy provision (CP).

Question 9

What is exercise above critical power characterised by?

Answer 9

A progressive increase in energy requirement during constant-power exercise.

Question 10

What does exercise below CP allow steady state to be achieved in?

Answer 10

Muscle and pulmonary gas exchange, arterial blood lactate concentration, arterial acid-bases status, muscle [PCr], muscle [Pi] and intramuscular pH.

Question 11

In very-heavy intensity what does the rate of energy requirement do and what does the rate of energy provision consequently do?

Answer 11

Progressively increases, also has to rise to meet requirements.

Question 12

What energy systems are integrated to provide ATP for very-heavy intensity exercise?

Answer 12

PCr, glycolytic and aerobic systems.

Question 13

What is glycolysis maximal rate of ATP provision relative to oxidative metabolism?

Answer 13

High

Question 14

What is the glycogen store in the liver and in the muscle?

Answer 14

100g in liver and 400-500g in muscle.

Question 15

What are the main substrates for glycolysis?

Answer 15

Glucose from the blood and glucose store in muscle (and liver).

Question 16

Does glycogen occupy a low or high volume?

Answer 16

Low

Question 17

What mass of water is retained per gram of glycogen stored?

Answer 17

~2-3g

Question 18

What is the net yield of ATP in glycolysis if the substrate is a) glucose or b) glycogen?

Answer 18

a) 2 or b) 3

Question 19

What does glycolysis also do when glycogen is the substrate?

Answer 19

Sequesters Pi

Question 20

What are the two shuttles used to shuttle NADH ?

Answer 20

Malate-aspartate shuttle and a-glycerophosphate shuttle

Question 21

Which shuttle is reversible?

Answer 21

Malate-aspartate shuttle

Question 22

Which is the dominant shuttle in a) type 1 and b) type 2 fibres?

Answer 22

a) malate-aspartate

b) a-glycerophosphate

Question 23

How does the malate-aspartate transfer electrons?

Answer 23

From the cytosol to NAD+ in the matrix

Question 24

How does the a-glycerophosphate transfer electrons?

Answer 24

From the cytosol to FAD in the inner membrane.

Question 25

Which shuttle produces the most ATP per 2 electrons?

Answer 25

Malate-aspartate yields 2.5, a-glycerophosphate yields 1.5.

Question 26

At exercise onset under what conditions would lactate production increase?

Answer 26

If glycogen phosphorylase and PFK activity outstrips pyruvate dehydrogenase activity.

Question 27

What is the structure of LDH?

Answer 27

A tetramer of four monomers, each can be one of two isoforms; heart or muscle.

Question 28

Which isoform of LDH is more sensitive to pyruvate inhibition and is less prone to lactate formation?

Answer 28

Heart

Question 29

Which isoform of LDH has a greater affinity for pyruvate and is postulated to promote lactate formation?

Answer 29

Muscle

Question 30

Which muscle fibre type has more LDH, and more in the M-isoform?

Answer 30

Muscle

Question 31

How can lactate be cleared?

Answer 31

By the intracellular lactate shuttle; a monocarboxylate symporter.

Question 32

In the monocarboxylate what is the charged lactate ion transported with?

Answer 32

A proton

Question 33

What happens to the lactate ion once transported?

Answer 33

It is oxidise by highly oxidative skeletal muscle, cardiac muscle or other tissues with low [La]

Question 34

What is controversial about the lactate shuffle?

Answer 34

Intracellular lactate shuttle to mitochondria

Question 35

What reduces lactate clearance?

Answer 35

a-adrenergic activity by causing vasoconstriction in the liver, kidney and inactive muscle and adrenaline reduces uptake by muscle.

Question 36

Why may bicarbonate be ingested?

Answer 36

It has been suggested to reduce pH during intense exercise and therefore causes a an increase in the extracellular buffering capacity and lower H+ allowing protons to leave the muscles at a faster rate.

Question 37

What may PCr act to communicate between?

Answer 37

The ATPase and the mitochondrion.

Question 38

Where is ATPase and mitochondrion communication thought to be better developed?

Answer 38

In type 1 muscle fibres, perhaps due to the greater glycolytic flux.