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Energy Expenditure at Rest & Physical Activity. McArdle, Katch, & Katch Chapter 8. Energy Expenditure at Rest. Basal Metabolic Rate BMR is rate of energy expenditure fasted , rested and supine conditions in thermoneutral environment.

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energy expenditure at rest physical activity

Energy Expenditure at Rest & Physical Activity

McArdle, Katch, & Katch

Chapter 8

energy expenditure at rest
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).
    • 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
energy expenditure at rest1
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 woman’s larger percent body fat & smaller muscle mass.
energy expenditure at rest2
Energy Expenditure at Rest
  • Estimate Resting Daily Energy Expenditure
    • Estimate kcal expenditure during rest by multiplying one’s 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.
energy expenditure at rest3
Energy Expenditure at Rest

Components of Total Daily Energy Expenditure

  • Physical Activity: 15-30% of TDEE
  • Dietary Induced Thermogenesis (~10% TDEE)
    • Thermic effect from processes of digesting, absorbing, & assimilating nutrients.
    • Thermogenesis reaches maximum w/i1 hr post
    • Thermogenesis can vary 10%-35% of ingested food energy
  • Resting Metabolic Rate
energy expenditure at rest4
Energy Expenditure at Rest
  • Factors affecting Total Daily Energy Expenditure
    • Climate.
      • RMR of people in tropic climate averages 5-10% higher.
      • RMR in extreme cold can triple.
    • Pregnancy.
energy expenditure in physical activity
Energy Expenditure in Physical Activity
  • Expression of Energy Expenditure
    • Total (gross) – Resting energy expenditure (REE) = Net energy cost of the activity per se.
    • Recovery energy included in Total = exercise energy + recovery energy.
    • Utilization of 1 liter of O2 generates about 5 kcal of energy.

Net O2 cost of exercise = exercise VO2 + recovery VO2 – (resting VO2 x time)

energy expenditure in physical activity1
Energy Expenditure in Physical Activity
  • Energy expended during weight-bearing activities increases proportional to body mass.
  • There is little relationship between body mass and energy expended during non-weight-bearing activities.
energy expenditure in physical activity2
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 because of one’s physical activity; average person spends ___% day sedentary.
energy expenditure in physical activity3
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 person’s resting metabolism or VO2

1 MET =

3.5 mlkg-1min-1

energy expenditure in physical activity4
Energy Expenditure in Physical Activity
  • Classification of Work
    • Intensity of Work often related to Heart Rate because of linear relationship to oxygen uptake.
economy efficiency of energy expenditure
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
economy efficiency of energy expenditure1
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.
energy expenditure during walking running and swimming
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.
energy expenditure during walking running and swimming1
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.
energy expenditure during walking running and swimming2
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.
energy expenditure during running
Energy Expenditure during Running
  • More economical to discontinue walking and begin to run or jog at speeds > 6.5 kmh (4 mph).
  • Net energy cost of running a given distance is independent of speed (pace).
  • 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.
energy expenditure during swimming
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
energy expenditure during swimming1
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.
illustration reference
Illustration Reference
  • McArdle, William D., Frank I. Katch, and Victor L. Katch. 2006. Essentials of Exercise Physiology 3rd ed. Image Collection. Lippincott Williams & Wilkins.