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