CHAPTER 4 Flashcards
What is energy?
capacity to do work aka mechanical energy
Is work=force x d mechanical energy?
yes
Is power = work/time mechanical energy?
yes
What is mechanical energy?
muscle contraction
What is chemical energy?
glucose and ATP
What is energy expenditure equation?
energy/time in kj or kcal/unit
calorie
Energy needed to raise the temperature of 1 g water 1oC.
Calorie
expressed on food labels
Joule
energy required to move a mass of 1 g at a velocity of 1 m/s.
1 cal = ______ Joules
4.186
1 kilocalories = ____ kilojoules
4.186
Is energy lost when converted from one form to another? Give example
no
CHO and fat combustion cause muscle contraction and rest goes to heat energy
Joule provides what kind of energy
mechanical
Energy efficiency: chemical or mechanical energy?
BOTH
Energy efficiancy
% of total work
20% is what we use for human work
remaining 80% as heat (homeostasis)
Gross efficiency
ratio of total work to energy expended
GE=work/energy expended X 100%
For GE: as exercise intensity increases, energy expended __________(increases /decreases). ultimately, GE gets bigger or smaller?
energy expended decreases, so your GE will increase
Net efficiency
baseline is the energy expended at rest to resolve GE getting bigger
NE = work accomplished / (energy expended-resting energy ependiture) X 100%
Work efficiency
another way to calculate baseline where baseline is the energy cost of unloaded work
WE = work accomplished/ (energy expended-energy expended in unloading condition) X 100%
Delta efficiency
change in energy expenditure relative to the change in actual work accomplished per minute
DE: delta work accomplished/delta energy expended X 100%
Atwater factors for CHO, fat and protein
CHO=4kcal/g
Fat=9kcal/g
Protein=4kcal/g
Coefficient of digestibility for CHO, fat and protein
Carb 97%
Fat 95%
Protein 92%
Does fibre increase or decrease digestibility?
Fibre decreases digestibility
Energy content for fat depends on
structure of FA and TAG
Energy content for protein depends on
type of protein and ntirogen content
If theres nitrogen in protein, does it give more energy or less energy?
less,
nitrogen DOES NOT PROVIDE energy
What does the direct calorimeter test?
metabolic rate of person
Disadvantage of direct calorimetry
Not practical for field studies and assessment of energy expenditure during sport and exercise
Some have developed direct calorimetry suits with the same principles but allows measurements to be conducted outside. Suit may impede movement however
How does the direct calorimeter prevent heat loss?
recirculated o2 and co2, water filtered out, oxygen is added
What does the closed circuit spirometry measure? How???
02 uptake and co2 production
aka energy expenditure
measured by seeing the difference in 02 uptake and co2 given off into the filter and by measuring TEMPERATURE
Disadvantage of closed circuit calorimeter
not suitable for exercise esp high intensity
What does respiration chamber (indirect) measure?
complete energy balance
Disadvantage to resp chamber
expensive, unrealistic, requires highly trained
Does the resp chamber measure heat directly?
NO
What does the open-circuit spirometry measure?
changes in inhaled and exhaled ambient air
WHat can do you with results of open circuit after?
calculate RER
which is VCO2/VO2
Is open circuit indirect or direct?
indirect
Is resp chamber indirect or direct?
indirect
Explain douglas bag
-large plastic bags collect expired air
-after collection, bags are closed and then emptied into gas meter to measure total volume
-sample gas from bags analyzed for O2 and CO2 concentrations
Analyzers such as that seen in this picture can analyze CO2 and O2 breath by breath
Therefore, can look at rapid changes - can look at changes every few seconds to several minutes
REE is measured by direct or indirect calorimetry?
indirect
Conditions for resting energy expenditure
Resting in supine position >30 min before Fasting >12 h No exercised for >24-48 h No caffeine >4 h No nicotine >1 h No alcohol >48 h Darkened, quiet, thermoneutral environment Normal acid-base balance
What is RQ, what does it do?
resp quotient - ratio of CO2 production and O2 production that provides indication of primary substrate utilized during steady state exercise.
RQ of CHO
1 because oxygen molecules = co2 molecules
RQ of lipids
7 ish
What is expired represents the oxidation processes in the tissues for which 2
oxygen and N2
What is expired DOES NOT represents the oxidation processes in the tissues for which, and why?
CO2 because co2 release is based on bicarbonate pool. and the pool is sensitive to changes in acid base balance ebcause shifts in bicarbonate buffering system affects dissociation of gases
WHen is RER over 1?
hyperventilation (through lactic build up, you release co2) and lipogenesis
What is doubly labelled water?
administer a bolus dose of 2 stable isotope water
difference between the 2 excretion rates repesent the co2 production rate, then co2 can be used to calculate EE
advantage: can be done on free living people
disadvantage of doubly labelled water
expensive, only suitable for measurement over days or weeks
Sedentary (little or no exercise):
1.2
Lightly active (1-3 days/week):
1.375
Moderately active (3-5 days/week):
1.55
Very active (6-7 days a week):
1.725
Extra active (physical job or 2x training):
1.9
BMR
measured lowest oxygen uptake in resting thermoneutral conditions
RMR
energy required for the maintenance of normal body functions and homeostasis in resting conditions
if you are sedentary is your RMR larger or smaller than people who are very active?
larger
factors that affect energy balance
Weight Body composition Sex Activity intensity/type Age Genetics
what is energy balance?
balance calculated over longer periods
what’s a good indicator of energy balance?
Wt
BMR units
J/s
which efficiency is best at rest
gross
which efficiency is best during exercise
delta efficiency
labeled bicarbonate
Constant infusion of bicarbonate labeled (13C or 14C) to reach equilibrium with body’s CO2 pool
- then any change results in changes in labeled CO2 production
- applied for short period (hours/days)
heart rate monitoring
- HR – linear relationship with O2 uptake at submax exercise
- less accurate especially at low levels of EE as at rest only slight movements increase HR but EE is same, emotions also change HR but not O2
accelerometers
Movement along 1, 2 or 3 axes
Correlate well with EE but may underestimate
Rough estimate or indication of EE
activity records
rough estimation, ppl tend to overestimate or underestimate PA
