Oklahoma State University Physiology of Exercise EPOC Calculations Discussion

LABORATORY 6
Oxygen Deficit and
EPOC Evaluations
Objectives
emonstrate measurement of O2 deficit and EPOC
raw and label O2 deficit and EPOC graph
alculate O2 deficit and EPOC
iscuss biochemical concepts related to O2 deficit and
EPOC
Introduction
nergy (ATP) provided through oxidative phosphorylation
at rest
TP requirements increase in rest-to-exercise transitions
ew ATP demand is not immediately met by oxidative
pathways
Metabolic Pathway Terminology
xidative phosphorylation
roduction of ATP using oxygen as final electron acceptor
hosphocreatine (PCr)
igh-energy phosphate that can donate phosphate group to ADP
sed to make ATP without oxygen
hort term (~10 s)
(continued)
Metabolic Pathway Terminology (continued)
naerobic glycolysis
rovides energy quickly
o oxygen
roduces lactate
actate accumulation
uild up of lactic acid
aused by a greater reliance on fast-glycolysis
Transition From Rest to Exercise
TP demand immediately increases to the level required for
work output
elay in measured oxygen uptake response
TP supplemented by short-term sources
hosphocreatine (PCr)
naerobic glycolysis
(continued)
Transition From Rest to Exercise (continued)
pproximately 3 minutes into activityøygen
consumption plateaus
TP demand is again met aerobically
xygen deficit = volume of oxygen missing from the start
of exercise to the plateau (figure 6.1)
(continued)
Transition From Exercise to Rest
2 uptake does not fall immediately back to resting at end
of exercise
ecreases over minutes or hours
xygen debt = volume of oxygen consumed above the
resting value during recovery
xcess post-oxygen consumption (EPOC)
Oxygen Consumption
Practical Example of Oxygen Deficit
ubject straddling a treadmill
ow energy demand
3.5 ml ? kg?1 ? min?1 = 1 MET
ubject steps onto treadmill and moves at moderate pace
nergy requirement (ATP demand) increases
quare wave
xidative phosphorylation does not immediately meet ATP
demand
(continued)
Practical Example of Oxygen Deficit (continued)
erobic system must be stimulated to meet new ATP
production
ntil then, body increases reliance on anaerobic pathways
Factors Influencing Oxygen Deficit
xygen deficit depends on factors
xercise intensity
enetics
itness levels (figure 6.3)
rained person shows less lactate accumulation and PCr
depletion
ess fatigue
Relationship Between Exercise Time and
Oxygen Uptake
Oxygen Uptake During Exercise and
Recovery
ast and slow portion of oxygen uptake
ast component
apid reestablishment of PCr and oxygen stores
low component
pproximately 20% used to clear lactic acid from blood by liver
through gluconeogenesis (Cori cycle)
est due to other processes
(continued)
Oxygen Uptake During Exercise and
Recovery (continued)
teady-state oxygen consumption (figure 6.2a)
nergy required is provided by oxidative phosphorylation
? ?? represents total energy expenditure
????
Oxygen Consumption and Requirements
Oxygen Consumption and Requirements
Oxygen Uptake During Recovery
xygen uptake (EPOC) falls quickly in the first 2 to 4 min
after exercise cessation
t then falls more slowly until it reaches the preexercise
value
xygen uptake can remain elevated during recovery
Factors Affecting Oxygen Uptake During
Recovery
eart rate
reathing rate
ody temperature

uscle inflammation
ormone levels
eestablishment of ion gradients
Magnitude of EPOC
etermined mainly by exercise intensity
igher intensity causes greater HR changes, ventilation,
body temperature, and hormone levels
reater deficit and EPOC
rimarily anaerobic exercise will result in most of the bout
being in oxygen deficit (figure 6.2b)
Example: 100 m Dash (Figure 6.4)
xygen consumption contributes little to energy
expenditure
naerobic pathways
pproximately 10 to 13 seconds
? ?? continues to rise after bout
????

ay take awhile to return to baseline
Oxygen Debt and the 100 m Dash
eestablishment of PCr contributes majority of EPOC
hort duration
lmost all exercise involves mix of three energy pathways
eightlifting
ntermittent sports

uscle repair following muscle-damaging exercise also
contributes to EPOC
levated O2 consumption for 48 h
Oxygen Deficit and EPOC for a 100 m Dash
Sample Estimation of Oxygen Deficit

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