Energy Expenditure.ppt

Energy Expenditure basics have been explained

1. Energy Expenditure at
Rest & Physical Activity
McArdle, Katch, & Katch
Chapter 8

2. Energy Expenditure at Rest
Basal Metabolic Rate
BMR is rate of energy expenditure fasted, rested and
supine conditions in thermoneutralenvironment.
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

3. 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/m
2
per
hour for men and 36 kcal/m
2
for women.
Lower BMR in women can be attributed to woman’s
larger percent body fat & smaller muscle mass.

4. 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/m
2
per
hour by 24 hrs.
Also possible to use Harris
Bennedict formulas.
Estimated values w/i ±5%
measured values.

5. Energy Expenditure at Rest
Components of Total Daily
Energy Expenditure
Physical Activity: 15-30% of
TDEE
Dietary Induced Thermogenesis
(~10% TDEE)
Thermiceffect from processes of
digesting, absorbing, &
assimilating nutrients.
Thermogenesisreaches maximum
w/i1 hr post
Thermogenesiscan vary 10%-
35% of ingested food energy
Resting Metabolic Rate

6. 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.

7. 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 O
2generates about 5kcal of
energy.
Net O
2cost of exercise = exercise VO
2+ recovery
VO
2–(resting VO
2x time)

8. 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.

9. Energy Expenditure in Physical Activity
Average daily Total Energy Expenditure estimated to
be 2900 –3000 kCalfor males, and 2200 kCalfor
females 15-50 y.o.a.
Great variability exists because of one’s physical
activity; average person spends ___%day sedentary.

10. Energy Expenditure in Physical
Activity
Classification of Work Factors:
Duration (min) and Intensity (VO
2& kCal)
A METis a measure of activity intensity & represents
an average person’s resting metabolism or VO
2
1 MET=
3.5 mlkg
-
1
min
-1

11. Energy Expenditure in Physical
Activity
Classification of Work
Intensity of Work often
related to Heart Rate
because of linear
relationship to oxygen
uptake.

12. 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:
1.Gross
2.Net
3.Delta

13. Economy & Efficiency of Energy
Expenditure
Grossefficiency uses total oxygen uptake.
Work Output
Energy Expended
Netefficiency subtracts resting VO
2from total.
Work Output
Energy Expended Above Rest
Deltaefficiency computes relative energy cost of
performing an additional increment of work.

14. 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.

15. 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 economicaland
relationship curves in upward
direction.

16. 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.

17. 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 VO
2more than
shortening below optimum (and increasing stride
frequency).
Cost of running into headwind significantly greater
than the reduction with tailwind.

18. 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

19. 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.

20. Illustration Reference
McArdle, William D., Frank I. Katch, and Victor
L. Katch. 2006. Essentials of Exercise Physiology
3
rd
ed. Image Collection. Lippincott Williams &
Wilkins.