Energy Expenditure
Energy Expenditure at Rest
® Basal
Metabolic Rate – energy requirement at rest in the “wakened” state
® No
food consumed for at least 12 hours prior to measurement (post-absorptive
state)
® No
exercise for at least 12 hours prior to measurement
® Measurement
taken once individual has been lying down quietly for 30-60 minutes
What influences BMR?
®
Body size
®
Due to average
difference in size, BMR is 5-10% lower in women compared to men
®
Age
®
As we get older,
BMR decreases
®
Smoking
®
Increases rate at
which body burns calories
®
Drugs
®
Certain drugs
increase BMR such as amphetamines
Total Energy Expenditure
® Resting
+ Daily activity = total daily energy expenditure (TDEE)
Factors affecting TDEE
®
Physical Activity
®
Accounts for
15-30% of TDEE
®
Diet
®
Consuming food
increases body’s TDEE, usually reaching a maximum 1 hour after eating
®
Accounts for
10-35% of TDEE; high protein diets may elicit up to 25% of food’s thermic
effect
®
Climate
®
Tropical climates
can increase energy expenditure by 5-20%
®
Shivering in cold
environments can ↑ TDEE
®
Pregnancy
®
Increases TDEE
due to body size and fetus
Energy Expenditure during Exercise
®
For each liter of
O2 consumed during exercise, we burn ~ 5 calories
®
Therefore, if an
individual jogs for 30 minutes and consumes 2 liters of O2/min, how
many calories did this person burn?
®
2 liters of O2/min
x 5 = 10 calories, then
®
10 calories x 30
minutes = 300 total calories expended during the 30 min exercise
®
Consideration
®
Must
account for BMR during the 30 min; so if it is 40 calories, net energy
expenditure would be 260 calories.
®
Quick note: About 100 calories are burned per 1 mile of walking
Average Daily Energy Expenditure Rates
® 2900
to 3000 calories for males aged 15-50 years
® 2200
for females aged 15-50 years
® Typical
person spends 75% of their day in sedentary activities
Classifying Work/Exercise
®
Physical Activity
Ratio (energy required/resting energy)
®
Light work = 3
times the energy of resting
®
Heavy work = 6 to
8 times the energy of resting
®
Maximal work = 9
times or more above resting
®
MET (metabolic
equivalent)
®
1 MET is the
amount of energy required at rest
®
1 MET = 3.5
ml/kg/min of O2 consumed
®
Example- 10 METS
is the amount of energy required at 10 times resting level. It would be equal to 35 ml/kg/min
Factors affecting energy expenditure during exercise
®
Body mass
®
the larger individual
expends more calories
®
Terrain and
walking surface
®
uneven terrain (e.g. beach or snow) ↑ calories
expended
®
Footwear
®
soft-soled shoes ↓ calories expended
®
Wearing
ankle/torso wts or using hand-held wts ↑ energy expended
®
Caution
!!!!!!!!
l
Wearing
ankle/torso wts put extreme stress on leg joints
l
Hand-held wts can ↑
blood pressure
Energy Expenditure of Running
® Considerations:
® Stride
length, frequency and speed will affect amount of energy used
® Running
style is individualistic
® Avoid
telling someone to lengthen stride when tired because this will make them more
inefficient and cause them to expend more energy
Energy Expenditure of Running
®
More
considerations
®
Air resistance –
account for by:
®
Air density – denser air ↑ energy need; thus higher
altitudes give less resistance
®
Runner’s
surface area - ↑ energy need;
wearing body-fitted clothing helps
®
Square of
headwind velocity - ↑ energy
need; running against headwind is not equally counterbalanced by running with
headwind
l
Drafting – can
save up to 26-38% of energy when staying behind competitor in cycling
Energy Expenditure of Swimming
®
Requires 4 times
more energy than running to cover the same distance
®
Factors
contributing to energy cost:
®
Wave drag – waves in front and back of swimmer
®
drafting eases energy
expenditure
®
Skin friction – uneven surface &/or body hair
®
wet suits provide
smooth surface
®
Streamlining – less “side to side” or “crooked” body position
®
Buoyancy – body fat provides advantage to floating
®
Women have
advantage over men in most cases
®
Swimmers may
maintain more body fat for protection against cold water