Biochemistry of the Endurance Athlete Flashcards
Define VO2max?
The upper limit of oxygen transport and utilisation attainable in any individual.
What is a requirement to maximise endurance exercise performance?
A high capacity for oxidative metabolism.
What does it cost to generate an ATP in terms of protons during substrate oxidation?
4
Per molecule of oxygen what does NADH and FADH2 yield in terms of ATP?
NADH= 2.5 FADH2= 1.5
What does the maximal forward flux, VO2max, of the oxidative phosphorylation reaction using NADH as its electron source depend on?
Non-O2 dependent factors: biochemical factors that limit the rate of substrate availability and O2 dependent factors: limit the rate of oxygen delivery to the mitochondria. Convective in the blood and diffusive between the capillary and mitochondria.
What are O2 dependent and dependent factors influenced by?
Muscle fibre type
In what oxygen state is lactate threshold increased in endurance trained athletes?
In hyperoxia
How does hyperoxia affect the lactate threshold in untrained individuals?
It is unchanged compared to normoxia.
What may reflect the effect of hypoxia and hyperoxia in untrained and endurance trained athletes?
May reflect that VO2max ad lactate threshold in untrained is limited to muscle O2 utilisation but in trained O2 delivery is the limiting factor.
May reflect the limitation of mitochondrial NADH oxidation, causing an increase in cytosolic redox potential and increasing [lactate]/[pyruvate]
How is VO2 controlled by PCr?
By the phosphorylation potential [ATP/[ATP][Pi] exerted through changes in [ADP].
[ATP] is constant and [Pi] is well above its Km.
What does the phosphorylation potential exert tight control over during endurance exercise?
Oxidative phosphorylation, when NADH and oxygen are in abundance (sometimes limited)
How does the redox potential [NADH]/[NAD+] in the TCA cycle limit oxidative phosphorylation in endurance exercise?
The allosteric activation of the three non-equilibrium reactions in the TCA-cycle (ICD, alpha-KD, CS) and of PDH.
How was VO2 limitation by the redox potential measured?
Cycle ergomety to exhaustion at 70 % VO2max and muscle biopsies at rest, 5 mins, 15 mins and exhaustion to measure TCA cycle intermediates.
