Energy Transfer in Exercise

Immediate Energy

ATP-CP stored in musclesprints heavy weightliftingevents < 10-15 seconds

Short-Term Energy

Lactic AcidAnaerobic Glycolysis LAIntermediate energy sourceMaximal intensity for 60-180

seconds400 meter run100 meter swim

Blood Lactate Concentration

25 50 75 100

Blo

od L

acta

te C

once

ntra

tion

Percent VO2 max

Untrained Threshold

Trained Threshold

TrainedUntrained

Factors Related to Lactate Threshold

Low tissue O2 (hypoxia)

Dependence on glycolysis

Activation of FT muscle fibers

Reduced ability to remove lactate

Training the Lactate Threshold

Training can threshold by 20-30%

genetics training effect of producing less LAtraining effect of more efficient LA

removal

Long-Term EnergyO

xyge

n U

ptak

e (m

l / k

g-m

in)

0 2 4 6

Exercise Time (min.)8

5

10

15

20

Trained

Untrained

Steady State/Rate

Initiation of Exercise

O2 uptake rises exponentially

Plateau is reached between 3-4 minutes

Oxygen Deficit

Quantity of O2 that would have been consumed had steady state been reach immediately

Oxygen Deficit

Endurance training reach steady-state sooner total O2 consumption is anaerobic component

VO2max

With progressively demanding aerobic exercise, region where O2 uptake plateaus

Represents an individual’s capacity for aerobic resynthesis of ATP

Helps determine one’s ability to sustain high intensity exercise for longer than 4-5 minutes

Energy Spectrum

Duration of Maximal Exercise

Seconds Minutes

10 30 60 2 4 10 31 60 120

%Anaerobic 90 80 70 50 35 15 5 2 1

%Aerobic 10 20 30 50 65 85 95 98 99

Energy Spectrum

Maximal Exercise Time (minutes)

Per

cent

of

Tot

al E

nerg

y Y

ield

50

100

603010

O2 Dept

Exercise Time

O2 C

onsu

mpt

ion

O2 deficit O2 requirement

Resting O2 consumption

Start Exercise End Exercise

Steady-state O2 consumption

End Recovery

O2 Dept

Classic O2 Dept (EPOC) Theory

Fast component – represents O2 required to rebuild ATP and CP

Slow component – removal of tissue lactate via conversion to glycogen or oxidation to CO2 and H2O

Contemporary EPOC Theory

Short duration, light to moderate exercise

Recovery O2 serves to replenish high-energy phosphates (several minutes

Contemporary EPOC Theory

Longer duration, high intensity aerobic exercise

Much longer period of O2 uptake

Some used for lactate glycogen

Causes of EPOC following Heavy Exercise

Resynthesize ATP and CPResynthesize lactate to glycogenOxidate lactate in energy metabolismRestore O2 to bloodThermogenic effects of elevated core temp.Thermogenic effects of hormonesEffects of HR, ventilation, & other

functions.

Recovery

Steady state aerobic exercise or 5 to 10 second bouts of maximal exercise not lactate accumulation recovery is rapid

Fast component

Recovery

Longer periods of anaerobic exercise

Lactate accumulation

Fast and slow components

Recovery

Exercise at 50% of VO2max can be continued at steady-state w/o build up

At 60-75% of VO2max – no steady-state lactate accumulates

Lactate removal is accelerated by aerobic exercise