Energy Expenditure at Rest

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Energy Expenditure at Rest Physical Activity

• McArdle, Katch, Katch
• Chapter 8

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Energy Expenditure at Rest

• Basal Metabolic Rate
• BMR is rate of energy expenditure fasted, rested
  and supine conditions in thermoneutral
  environment
• Resting metabolic rate (RMR) is rate of energy
  expenditure when at rest but not basal
• BMR proportional to BSA, after age 20 ? 2 3
  per decade in women and men, respectively
• When RMR expressed per unit LBM, no difference
• BMR represents largest fraction of TEE in
  sedentary

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Energy Expenditure at Rest

• Influence of Body Size
• Differences in body size usually expressed in
  terms of body surface area (BSA).
• From 20-40, average values BMR are 38 kcal/m2 per
  hour for men and 36 kcal/m2 for women.
• Lower BMR in women can be attributed to womans
  larger percent body fat smaller muscle mass.

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Energy Expenditure at Rest

• Estimate Resting Daily Energy Expenditure
• Estimate kcal expenditure during rest by
  multiplying ones surface area from nomogram by
  appropriate kcal expenditure/m2 per hour by 24
  hrs.
• Also possible to use Harris Bennedict formulas.
• Estimated values w/i 5 measured values.

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Energy Expenditure at Rest

• Factors Affecting Total Daily Energy Expenditure
• Physical Activity 15-30 of TDEE
• Dietary Induced Thermogenesis
• Thermic effect from processes of digesting,
  absorbing, assimilating nutrients.
• Thermogenesis reaches maximum w/i 1 hr post
• Thermogenesis can vary 10-35 of ingested food
  energy

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Energy Expenditure at Rest

• Factors affecting Total Daily Energy Expenditure
• Climate.
• Pregnancy.

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Energy Expenditure in Physical Activity

• Expression of Energy Expenditure
• Total (gross) Resting energy expenditure (REE)
  Net energy expenditure of the activity per se.
• Recovery energy included in Total exercise
  energy recovery energy.
• Measure VO2 during an activity and recovery
  multiplied by 5 kcal per liter yields gross
  energy expenditure.

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Energy Expenditure in Physical Activity

• Energy expended during weight-bearing activities
  increases proportional to body mass.
• Energy expended during non-weight-bearing
  activities has little relationship to body mass.

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Energy Expenditure in Physical Activity

• Average daily Total Energy Expenditure estimated
  to be 2900 3000 kCal for males, and 2200 kCal
  for females 15-50 y.o.a.
• Great variability exists and largely determined
  by ones physical activity.

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Energy Expenditure in Physical Activity

• Classification of Work Factors
• Duration (min) and Intensity (VO2 kCal)
• A MET is a measure of activity intensity
  represents an average persons resting metabolism
  or VO2

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Energy Expenditure in Physical Activity

• Classification of Work
• MET 3.5 mL O2 ? kg-1 ? min-1, 1 kCal ? kg-1 ?
  hr-1
• Intensity of Work often related to Heart Rate
  because of linear relationship to oxygen uptake.

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Economy Efficiency of Energy Expenditure

• Mechanical Efficiency Work Output Energy
  Input (expenditure).
• Work Output Force x Distance
• kg ? m or ft ? lb.
• Three efficiency terms
• Gross
• Net
• Delta

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Economy Efficiency of Energy Expenditure

• Gross efficiency uses total oxygen uptake.
• Work Output
• Energy Expended
• Net efficiency subtracts resting VO2 from total.
• Work Output
• Energy Expended Above Rest
• Delta efficiency computes relative energy cost of
  performing an additional increment of work.

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Energy Expenditure during Walking, Running, and
Swimming

• Economy is relationship between
• Energy output
• Energy input
• Greater economy requires less oxygen uptake to
  perform a task.
• Training adjustment that improves economy
  directly relates to improved exercise performance.

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Energy Expenditure during Walking, Running, and
Swimming

• Energy Expenditure during Walking
• Relationship between walking speed and oxygen
  uptake essentially linear between speeds of 3.0
  and 5.0 kilometers per hour (1.9 to 3.1 mph).
• At faster speeds, walking becomes less economical
  and relationship curves in upward direction.

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Energy Expenditure during Walking, Running, and
Swimming

• Walking on snow and sand requires about twice the
  energy expenditure of walking on hard surfaces.
• Energy cost is proportionally larger for larger
  people.
• Hand-held weights increases energy cost of
  walking but may disproportionately elevate
  systolic blood pressure.

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Energy Expenditure during Running

• More economical to discontinue walking and begin
  to run or jog at speeds gt 6.5 kmh (4 mph).
• Net energy cost of running a given distance is
  independent of running speed.
• Lengthening stride above the optimum length (and
  reducing stride frequency) increases VO2 more
  than shortening below optimum (and increasing
  stride frequency).
• Cost of running into headwind significantly
  greater than the reduction with tailwind.

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Energy Expenditure during Swimming

• Energy expenditure to swim a given distance is
  about 4 times greater than to run same distance.
• Energy must be expended to maintain buoyancy
  while generating horizontal motion and to
  overcome drag forces.
• Total drag consists of
• Wave drag
• Skin friction drag
• Viscous pressure drag

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Energy Expenditure during Swimming

• Elite swimmers expend fewer calories to swim a
  given stroke at any velocity.
• Women swim a given distance at lower energy cost
  than men because of greater buoyancy.

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Illustration Reference

• McArdle, William D., Frank I. Katch, and Victor
  L. Katch. 2000. Essentials of Exercise
  Physiology 2nd ed. Image Collection. Lippincott
  Williams Wilkins.