Energy Expenditure During Rest and Physical Activity

Copyright © 2006 Lippincott Williams & Wilkins.

Energy Expenditure During Rest and Physical

Activity

Energy Expenditure During Rest and Physical

Activity Chapter 8Chapter 8


Basal Metabolic Rate (BMR)

Basal Metabolic Rate (BMR)

• The minimum energy required to sustain the body’s functions in the waking state


Basal Metabolic Rate (BMR) (cont’d)

Basal Metabolic Rate (BMR) (cont’d)

• Is assessed by measurement of under the following standardized

conditions– 12 hours postabsorptive– No undue muscular exertion for at least 12

hours prior to measurement– Measured after the person has been lying

quietly for 30 to 60 minutes in a dimly lit, temperature-controlled room

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Dietary-Induced Thermogenesis (DIT)

Dietary-Induced Thermogenesis (DIT)

• Consuming food increases energy metabolism as a result of the following energy-requiring processes – Digestion of nutrients– Absorption of nutrients– Assimilation of nutrients

• The magnitude of DIT ranges from 10 to 35% of the ingested food

• So…..why do people starve themselves to lose weight?


Thermic Effect of Physical Activity

Thermic Effect of Physical Activity

• Profoundly affects total daily energy expenditure (TDEE)

• Accounts for ~15 to 30% of TDEE


Effect of Body MassEffect of Body Mass

• Body size plays an important role in exercise energy requirements

• Energy expended during weight-bearing exercise increases directly with the body mass transported


Metabolic Equivalent (MET)

Metabolic Equivalent (MET)

• One MET represents an adult’s average, seated, resting oxygen consumption or energy expenditure– 1 MET ~ 250 ml/min – 1 MET = 3.5 ml/(kg•min)


Metabolic Equivalent (MET) (cont’d)

Metabolic Equivalent (MET) (cont’d)

• The MET provides a convenient way to rate exercise intensity with respect to a resting baseline– 2 MET = 7.0 ml/(kg•min) – 10 MET = 35.0 ml/(kg•min)


Heart Rate to Estimate Energy Expenditure

Heart Rate to Estimate Energy Expenditure

• HR and relate linearly throughout a broad range of aerobic exercise intensities

• Thus, HR may provide an estimate of (and energy expenditure) during physical activity

• However, factors other than influence HR response to exercise

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Energy Expenditure DuringWalking, Running, and

Swimming

Energy Expenditure DuringWalking, Running, and

Swimming


Factors Affecting Endurance Performance

Factors Affecting Endurance Performance

• Aerobic power ( )• Efficiency of energy use

– Muscle fibers, fitness level, body composition, technique, speed

• Economy of movement– Relationship between energy input and output– At a given submaximum speed of running, cycling, or swimming, an

individual with greater movement economy will consume less oxygen

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Who worked the hardest to finish?


Crossover velocity at 4.0 mph


Stride Length, Frequency, and Running Speed

Stride Length, Frequency, and Running Speed

• Running speed can increase in 3 ways– Increase stride frequency– Increase stride length– Increase both stride length and

frequency


Get with a partner• Children are less economical runners than adults and

require 20 to 30% more oxygen per unit of body mass to run at a given speed

• Swimming requires about four times more energy to swim a given distance compared to running

• Most people assume they expend more total calories if they run a given distance faster. Explain why this is not true. In what way does correcting this misunderstanding contribute to a recommendation for the use of exercise for weight loss?

• What circumstances would cause a particular exercise task to be rated “strenuous” in intensity by one person but only “moderate” by another?

• How would you react to the coach who says that “you can’t train speed, it’s a genetic gift”?


Energy Cost of DragEnergy Cost of Drag

• Three components comprise the total drag force that impedes a swimmer’s forward movement– Wave drag– Skin friction drag– Viscous pressure drag


Effects of Buoyancy: Men vs. Women

Effects of Buoyancy: Men vs. Women

• Women, on average, are more buoyant than men due to their greater fat mass

• The increased buoyancy translates to greater swimming economy

• The potential hydrodynamic benefit enjoyed by women becomes noteworthy during longer distances, when swimming economy takes on added importance

Energy Expenditure During Rest and Physical Activity

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