Flashcards in Lecture 10 - O2 uptake during exercise Deck (10)
For a given exercise intensity there is..
a particular oxygen uptake
how efficient are we at converting oxygen uptake to mechanical work
rest goes into heat
Why is there a lag in oxygen uptake at the onset of exercise or exercise transitions?
O2 utilisation - "metabolic inertia" - the mitochondrial respiration is a bit sluggish, takes times for enzymes to start working
An interaction between both mechanisms
What are some determinants of VO2 kinetics (and hence the lag period)
Ca2+ activation of mitochondrial dehyrogenases and ATP synthase
ATP/ADP * Pi and NAD+/NADH
Mitochondrial PO2 - getting the oxygen into the mitochondria
all of these contribute to the slow lag in o2 uptake
As you increase the exercise intensity, you also increase
the oxygen drift - the slow increase in oxygen uptake
What are some potential explanations to the VO2 drift in increasing intensity or duration exercise?
80% due to the active muscles
recruitment of lower efficiency type II fibres (which you need after a while)
Reduced OXPHOS coupling efficiency (the amount of ATP you get per oxygen decreases = P-O ratio)
Elevated muscle temp - changes the dynamics
O2 cost of ventilatory and cardiac work
You also need more oxygen to oxidise fat (which is used more later)
What happens in the period after exercise that requires Excess post-exercise oxygen consumption (EPOC)?
Resynthesis of ATP, CrP (happens quickly)
Restoration of myoglobin O2 stores - which normally serves as a buffer
Elevated HR, Ve temperature, hormones
Increased FFA metabolism
Glycogen resynthesis - happens quickly
What are some points on CrP resynthesis?
Occurs rapidly (t1/2 = 60-90s)
Influenced by Muscle oxidative capacity
What is the metabolic fate of lactate?
Oxidation in skeletal and cardiac muscle - with LDH enzyme
(active recovery enhanced lactate removal)
Substrate for glycogen synthesis
Conversion to other metabolites (AAs)
Does not increase VO2 or cause muscle soreness