Energy balance and substrate metabolism 2 Flashcards
What is measured in direct calorimetry?
The heat produced by someone
Issues with a direct calorimetry machine?
Need to be quite small (people cant move), very expensive
What does indirect calorimetry measure?
Oxygen consumption and carbon dioxide production
Ways to measure energy expenditure in free living conditionds?
Self report questionnaire, doubly labelled water, pedometers, accelerometers, accelerometry and heart rate combined (aciheart)
Benefits of self report energy expenditure?
Easy to administer to a large group, low cost
Issues of self report energy expenditure?
Reporting bias–> underreport intake and overreport exercise
Benefits of doubly labelled water?
Precise and accurate
Issues with doubly labelled water?
Expensive and technically challenging-> cannot be used on a large group
What does the AciHeart measure?
Accelerometry and heart rate
How does doubly labelled water work?
Ingest a dose of water with heavier H and O isotopes. O loss is steeper when measured as it is lost in CO2 and H20 whereas H is only lost in H2O. Difference between the two is the average CO2 produced over that time period
Strengths of DLW?
Doesnt need to rely on accurate patient reporting
Technical limitations of DLW?
Ratio of CO2 production to O2 consumption varied depending on diet of person, so O2 consumption isnt an exact measure it is inferred
Issue with using DLW at high exercise intensities?
High exercise intensity results in acidosis (H+ production) which is buffered by bicarbonate system–> produces CO2 from non-metabolic processes
Fuel source issue w/ DLW?
Can be oxidising things like lactate, ketone bodies, protein as well as Carbs and Fat
Tissue specific measurement of substrate metabolism method?
Tracer based–> infuse a labeled form of glucose into a vein, ingest another form of carb–> measure exogenous carb oxidation
What can be measured from tissue specific measurement of substrate metabolism?
Exogenous carb production
Link between exercise intensity and fuel consumption?
At higher intensity exercises, carbohydrate fuels are used more than fats
Effect of duration of exercise on fuel consumption?
Decrease in carb use and an increase in fat use
Which metabolic fuels are blood based?
Plasma glucose, circulating FFA
Contribution of muscle based fuels as exercise duration increases?
Decreases
Why does the contribution of muscle based fuels decrease as exercise duration increases?
Muscle fuels are depleted over the course of exercise so the longer it goes on the less readily available they are
What effect on fuel use does ingesting Cho have?
Decrease fat oxidation and increase carb oxidation
Which sex has the greater capacity for fat oxidation?
Women
Effect of VO2max on muscle glycogen storage?
Increases it
