exercise Flashcards
how does the human body perform exercise
muscle driver - consumes O2 and makes CO2
circulatory system
lungs
anaerobic metabolism/acidosis
Purpose of GE
Transport O2 to tissues
main aim removal of CO2
Respiratory quotient
CO2 production/O2 consumption
=1 = 1 CO2 for every O2
lipid RER 0.7 - more O2 for less CO2 - lung doesn’t have to work as hard
protein RER = 0.8
when RER>1 - anaerobin resp make CO2 but not using O2
RER in mouth
Rq cellular level
Flow of O2 and CO2
cog system
muscle produce CO2
cause CO2 flow through heart and blood and then expired
-ve pressure in chest - draw air in - dissolve into blood bound to Hb - through capillaries to tissues, CO2 goes the other way
Role of O2 in resp
required for the production of energy
Oxygen requirements
seated at rest need 3.55ml/min/kg of O2 goes up in metabolic equivalents (MET) standing 1.5MET walking 2 cycling >4 running >7
Muscles response to exercise
use stored energy - ATP and creatine phosphate for muscle contraction
inorganic phosphates, ADP and creatine drive ox phos
TCA and glycolysis increase
ox consumption increase at muscle
initially CO2 production only slightly increases - buffered as HCO3- then rises matching O2
O2 and CO2 levels in exercise
O2 increases 10ml/min/watt
build up deficit - need to pay back at end as O2 debt
in CVD - longer for blood to reach lung = larger debt
CO2 rises more slowly - more soluble so even though it is produced it is stored in tissues
Circulation response to incremental exercise
resting CO = 5L/min
almost linear increase in CO
plateau - body deliver as much O2 as it can - define max work load
O2 consumption limited by CO
O2 consumption increase linearly with the workload
anaerobic respiration contribute to small and inefficient part of metabolism
to increase O2 delivery - increase CO to max then HR
SV decrease as HR increase past point - filling time less
max HR
220-age
Oxygen consumption
increase in O2 consumption is double increase in CO
double O2 delivery = quadruple O2 consumption - because bigger conc grad, O2 diffuse more down, ODC facilitates this
mixed venous saturation drops from 75-80% at rest to 15-20% in exercise
up to 85% O2 can be extracted in exercise
Fick eqn
Oxygen consumption = Cardiac Output x (a-v) O2 Content
Lung response to incremental exercise
hyperventilate increases tidal vol
when reach max vol - increase the frequency
inefficient to breathe at vital capacity - roughly breathe at half
CO2 production drive ventilation
linear increae in ventilation for CO2 production
arterial PCO2 stays the same - so pH stays the same
VQ matching in exercise
at rest not ideal - PAO2 and PaO2 don’t match
early exercise - VQ improves PaO2
incremental aerobic respiration
aerobic respiration - O2 flow matches demand
RQ rises to 1 as glucose becomes the predominant fuel source
ventilation increases to match CO2 production and attempts to maintain steady state
Anaerobic metabolism
inefficient
central to human exercise physiology
short term solution when higher energy required
Bohr effect
extract more O2 - diffusion effect
when generate lactic acid - Hb affinity for O2 decreases - offload more
dealing with acidosis
lactate produces H+ buffered by bicarb HCO3- + H+ -- H2CO3 -- CO2 +H2O increased CO2 increased ventilation pH relatively stable H+ exceeds HCO2- hyperventilation relative to VCO2
why does hyperventilation in exercise cause exercise intolerance
causes low CO2 and high pH
O2 not released to muscles
what happens to VE, VCO2, VO2 in anaerobic resp
become acidotic and outstrip buffer
hyperventilate - sharp, non-linear increase in VE
get rid of more CO2 than make
more CO2 produced than oxygen consumed
QO2/CO2
at muscle
VO2/CO2
at mouth
VE
minute vent
PAO2/CO2
Alveolar partial pressure
