Biochemistry of the Middle Distance Athlete Flashcards
What is the critical power concept?
That every individual has a different power-duration relationship that produces a different hyperbolic curve and a distinct critical power.
In an endurance type athlete what type of expression do they have of muscle fibres compared to a sprint type athlete?
Low type 2
Which type of athlete, endurance or sprint, has a better developed anaerobic energy provision pathway?
Sprint
Which type of athlete, endurance or sprint, has a higher critical power asymptote?
Endurance
What does the critical power asymptote denote?
The upper limit for the attainment of steady state.
What is the length of a middle distance sporting event?
~2-30 minutes
What is the power-duration relationship equation?
W’ = Tlim x (W-CP)
What two parameters does the power duration relationship equation describe the tolerable duration of a constant power output in?
The capacity of anaerobic systems reflected by W’ and the upper limit for wholly aerobic energy provision (CP).
What is exercise above critical power characterised by?
A progressive increase in energy requirement during constant-power exercise.
What does exercise below CP allow steady state to be achieved in?
Muscle and pulmonary gas exchange, arterial blood lactate concentration, arterial acid-bases status, muscle [PCr], muscle [Pi] and intramuscular pH.
In very-heavy intensity what does the rate of energy requirement do and what does the rate of energy provision consequently do?
Progressively increases, also has to rise to meet requirements.
What energy systems are integrated to provide ATP for very-heavy intensity exercise?
PCr, glycolytic and aerobic systems.
What is glycolysis maximal rate of ATP provision relative to oxidative metabolism?
High
What is the glycogen store in the liver and in the muscle?
100g in liver and 400-500g in muscle.
What are the main substrates for glycolysis?
Glucose from the blood and glucose store in muscle (and liver).
Does glycogen occupy a low or high volume?
Low
What mass of water is retained per gram of glycogen stored?
~2-3g
What is the net yield of ATP in glycolysis if the substrate is a) glucose or b) glycogen?
a) 2 or b) 3
What does glycolysis also do when glycogen is the substrate?
Sequesters Pi
What are the two shuttles used to shuttle NADH ?
Malate-aspartate shuttle and a-glycerophosphate shuttle
Which shuttle is reversible?
Malate-aspartate shuttle
Which is the dominant shuttle in a) type 1 and b) type 2 fibres?
a) malate-aspartate
b) a-glycerophosphate
How does the malate-aspartate transfer electrons?
From the cytosol to NAD+ in the matrix
How does the a-glycerophosphate transfer electrons?
From the cytosol to FAD in the inner membrane.
Which shuttle produces the most ATP per 2 electrons?
Malate-aspartate yields 2.5, a-glycerophosphate yields 1.5.
At exercise onset under what conditions would lactate production increase?
If glycogen phosphorylase and PFK activity outstrips pyruvate dehydrogenase activity.
What is the structure of LDH?
A tetramer of four monomers, each can be one of two isoforms; heart or muscle.
Which isoform of LDH is more sensitive to pyruvate inhibition and is less prone to lactate formation?
Heart
Which isoform of LDH has a greater affinity for pyruvate and is postulated to promote lactate formation?
Muscle
Which muscle fibre type has more LDH, and more in the M-isoform?
Muscle
How can lactate be cleared?
By the intracellular lactate shuttle; a monocarboxylate symporter.
In the monocarboxylate what is the charged lactate ion transported with?
A proton
What happens to the lactate ion once transported?
It is oxidise by highly oxidative skeletal muscle, cardiac muscle or other tissues with low [La]
What is controversial about the lactate shuffle?
Intracellular lactate shuttle to mitochondria
What reduces lactate clearance?
a-adrenergic activity by causing vasoconstriction in the liver, kidney and inactive muscle and adrenaline reduces uptake by muscle.
Why may bicarbonate be ingested?
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.
What may PCr act to communicate between?
The ATPase and the mitochondrion.
Where is ATPase and mitochondrion communication thought to be better developed?
In type 1 muscle fibres, perhaps due to the greater glycolytic flux.
