Energy Energy Expenditure at Expenditure at Rest & Physical Rest & Physical

ActivityActivityMcArdle, Katch, & KatchMcArdle, Katch, & Katch

Chapter 8Chapter 8

Energy Expenditure at Energy Expenditure at RestRest

Basal Metabolic RateBasal Metabolic Rate BMR is rate of energy expenditure BMR is rate of energy expenditure fastedfasted, rested , rested

and supine conditions in thermoneutral and supine conditions in thermoneutral environment.environment.

Resting Metabolic Rate (RMR) is rate of Resting Metabolic Rate (RMR) is rate of energy expenditure when at rest but not energy expenditure when at rest but not basal (> BMR).basal (> BMR). BMR proportional to BSA, after age 20 BMR proportional to BSA, after age 20 2% & 3% 2% & 3%

per decade in women and men, respectivelyper decade in women and men, respectively When RMR expressed per unit LBM, no differenceWhen RMR expressed per unit LBM, no difference BMR represents largest fraction of TEE in BMR represents largest fraction of TEE in

sedentarysedentary

Energy Expenditure at Energy Expenditure at RestRest

Influence of Body SizeInfluence of Body Size Differences in body size usually Differences in body size usually

expressed in terms of body surface area expressed in terms of body surface area (BSA).(BSA).

From 20-40, average values BMR are 38 From 20-40, average values BMR are 38 kcal/mkcal/m22 per hour for men and 36 kcal/m per hour for men and 36 kcal/m22 for women.for women.

Lower BMR in women can be attributed Lower BMR in women can be attributed to woman’s larger percent body fat & to woman’s larger percent body fat & smaller muscle mass.smaller muscle mass.

Energy Expenditure at Energy Expenditure at RestRest

Estimate Resting Daily Estimate Resting Daily Energy ExpenditureEnergy Expenditure Estimate kcal expenditure Estimate kcal expenditure

during rest by multiplying during rest by multiplying one’s surface area from one’s surface area from nomogram by appropriate nomogram by appropriate kcal expenditure/mkcal expenditure/m22 per per hour by 24 hrs.hour by 24 hrs.

Also possible to use Harris Also possible to use Harris Bennedict formulas.Bennedict formulas.

Estimated values w/i ± 5% Estimated values w/i ± 5% measured values.measured values.

Energy Expenditure at Energy Expenditure at RestRest

Components of Total Daily Components of Total Daily Energy ExpenditureEnergy Expenditure Physical Activity: 15-30% Physical Activity: 15-30%

of TDEEof TDEE Dietary Induced Dietary Induced

Thermogenesis (~10% Thermogenesis (~10% TDEE)TDEE)

Thermic effect from Thermic effect from processes of digesting, processes of digesting, absorbing, & assimilating absorbing, & assimilating nutrients.nutrients.

Thermogenesis reaches Thermogenesis reaches maximum w/i maximum w/i 1 hr post1 hr post

Thermogenesis can vary 10%-Thermogenesis can vary 10%-35% of ingested food energy35% of ingested food energy

Resting Metabolic RateResting Metabolic Rate

Energy Expenditure at Energy Expenditure at RestRest

Factors affecting Factors affecting Total Daily Energy Total Daily Energy ExpenditureExpenditure Climate.Climate.

RMR of people in RMR of people in tropic climate tropic climate averages 5-10% averages 5-10% higher.higher.

RMR in extreme RMR in extreme cold can triple.cold can triple.

Pregnancy.Pregnancy.

Energy Expenditure in Energy Expenditure in Physical ActivityPhysical Activity

Expression of Energy ExpenditureExpression of Energy Expenditure Total (gross) – Resting energy expenditure Total (gross) – Resting energy expenditure

(REE) = Net energy cost of the activity per (REE) = Net energy cost of the activity per se.se.

Recovery energy included in Total = exercise Recovery energy included in Total = exercise energy + recovery energy.energy + recovery energy.

Utilization of 1 liter of OUtilization of 1 liter of O22 generates about generates about 55 kcal of energy.kcal of energy.

Net ONet O22 cost of exercise = exercise VO cost of exercise = exercise VO22 + + recovery VOrecovery VO22 – (resting VO – (resting VO22 x time) x time)

Energy Expenditure in Energy Expenditure in Physical ActivityPhysical Activity

Energy expended during weight-bearing activities Energy expended during weight-bearing activities increases proportional to body mass.increases proportional to body mass.

There is little relationship between body mass and There is little relationship between body mass and energy expended during non-weight-bearing activities.energy expended during non-weight-bearing activities.

Energy Expenditure in Physical Energy Expenditure in Physical ActivityActivity

Average daily Total Energy Expenditure estimated Average daily Total Energy Expenditure estimated to be 2900 – 3000 kCal for males, and 2200 kCal for to be 2900 – 3000 kCal for males, and 2200 kCal for females 15-50 y.o.a.females 15-50 y.o.a.

Great variability exists because of one’s physical Great variability exists because of one’s physical activity; average person spends activity; average person spends ___%___% day sedentary. day sedentary.

Energy Expenditure in Energy Expenditure in Physical ActivityPhysical Activity

Classification of Work Factors:Classification of Work Factors: Duration (min) and Intensity (VODuration (min) and Intensity (VO22 & kCal) & kCal)

A A METMET is a measure of activity intensity & represents is a measure of activity intensity & represents an average person’s resting metabolism or VOan average person’s resting metabolism or VO22

1 METMET =3.5 mlkg-

1min-1

Energy Expenditure in Energy Expenditure in Physical ActivityPhysical Activity

Classification of Classification of WorkWork Intensity of Work Intensity of Work

often related to often related to Heart Rate because Heart Rate because of linear of linear relationship to relationship to oxygen uptake.oxygen uptake.

Economy & Efficiency of Economy & Efficiency of Energy ExpenditureEnergy Expenditure

Mechanical EfficiencyMechanical Efficiency = Work = Work Output ÷ Energy Input Output ÷ Energy Input (expenditure).(expenditure).

Work Output = Force x DistanceWork Output = Force x Distance kg kg m or ft m or ft lb. lb.

Three efficiency terms:Three efficiency terms:1.1. GrossGross

2.2. NetNet

3.3. DeltaDelta

Economy & Efficiency of Economy & Efficiency of Energy ExpenditureEnergy Expenditure

GrossGross efficiency uses total oxygen uptake. efficiency uses total oxygen uptake.

Work OutputWork Output

Energy ExpendedEnergy Expended NetNet efficiency subtracts resting VO efficiency subtracts resting VO22 from from

total.total.

Work Output Work Output

Energy Expended Above RestEnergy Expended Above Rest DeltaDelta efficiency computes relative energy efficiency computes relative energy

cost of performing an additional cost of performing an additional increment of work. increment of work.

Energy Expenditure during Energy Expenditure during Walking, Running, and Walking, Running, and

SwimmingSwimming Economy is relationship betweenEconomy is relationship between

Energy outputEnergy output

Energy inputEnergy input Greater economy requires less Greater economy requires less

oxygen uptake to perform a task.oxygen uptake to perform a task. Training adjustment that improves Training adjustment that improves

economy directly relates to economy directly relates to improved exercise performance.improved exercise performance.

Energy Expenditure during Energy Expenditure during Walking, Running, and Walking, Running, and

SwimmingSwimming Energy Expenditure Energy Expenditure

during Walkingduring Walking Relationship between Relationship between

walking speed and walking speed and oxygen uptake oxygen uptake essentially linear essentially linear between speeds of between speeds of 3.0 3.0 and 5.0 kilometers per and 5.0 kilometers per hour (1.9 to 3.1 mphhour (1.9 to 3.1 mph).).

At faster speeds, At faster speeds, walking becomes less walking becomes less economicaleconomical and and relationship curves in relationship curves in upward direction.upward direction.

Energy Expenditure during Energy Expenditure during Walking, Running, and Walking, Running, and

SwimmingSwimming Walking on snow and sand requires about twice the Walking on snow and sand requires about twice the

energy expenditure of walking on hard surfaces.energy expenditure of walking on hard surfaces. Energy cost is proportionally larger for larger people.Energy cost is proportionally larger for larger people. Hand-held weights increases energy cost of walking but Hand-held weights increases energy cost of walking but

may disproportionately elevate systolic blood pressure.may disproportionately elevate systolic blood pressure.

Energy Expenditure during Energy Expenditure during RunningRunning

More economical to discontinue walking More economical to discontinue walking and begin to run or jog at speeds > 6.5 and begin to run or jog at speeds > 6.5 kmh (4 mph).kmh (4 mph).

Net energy cost of running a given Net energy cost of running a given distance is independent of distance is independent of speed (pace)speed (pace)..

Lengthening stride above the optimum Lengthening stride above the optimum length (and reducing stride frequency) length (and reducing stride frequency) increases VOincreases VO22 more than shortening below more than shortening below optimum (and increasing stride optimum (and increasing stride frequency).frequency).

Cost of running into headwind significantly Cost of running into headwind significantly greater than the reduction with tailwind.greater than the reduction with tailwind.

Energy Expenditure during Energy Expenditure during SwimmingSwimming

Energy expenditure to swim a given Energy expenditure to swim a given distance is about 4 times greater than distance is about 4 times greater than to run same distance.to run same distance.

Energy must be expended to maintain Energy must be expended to maintain buoyancy while generating horizontal buoyancy while generating horizontal motion and to overcome drag forces.motion and to overcome drag forces.

Total drag consists of:Total drag consists of: Wave dragWave drag Skin friction dragSkin friction drag Viscous pressure dragViscous pressure drag

Energy Expenditure during Energy Expenditure during SwimmingSwimming

Elite swimmers Elite swimmers expend fewer expend fewer calories to swim a calories to swim a given stroke at any given stroke at any velocity.velocity.

Women swim a Women swim a given distance at given distance at lower energy cost lower energy cost than men because than men because of greater of greater buoyancy.buoyancy.

Illustration ReferenceIllustration Reference

McArdle, William D., Frank I. Katch, McArdle, William D., Frank I. Katch, and Victor L. Katch. 2006. and Victor L. Katch. 2006. Essentials of Exercise PhysiologyEssentials of Exercise Physiology 3 3rdrd ed. Image Collection. Lippincott ed. Image Collection. Lippincott Williams & Wilkins.Williams & Wilkins.