Year 3 Week 1 Physiology
Measuring the fuels we use during exercise
Aims:
Different methods to investigate fuel metabolism
Advantages and Disadvantages
If we can quantify fuel utilisation we can apply this to optimise nutritional strategies and
training interventions for health and optimal performance
Contribution of each fuel source to EE is dependant on many factors
Intensity + Duration are two main
Gender
Training status
Nutrition
Whole body substrate use
How do we measure substrate oxidation in individuals?
Indirect calorimetry - Douglas bags (gold standard), metabolic cart, respiration chamber (rare
+ very expensive) stay in for 24/48/72hrs and measure expenditure after eating or whilst
sleeping etc.
RQ=CO2/02
Use this to calculate proportion of energy from carbs and fats/contribution of the two
If Glucose RQ=1 then 100% of energy is coming from CHO
If Fatty acids RQ=0.7 then 100% of energy is coming from fats
Usually somewhere in between
What does RQ represent?
O2 and CO2 exchange representative of combustion processes occurring in oxidative tissues
(e.g. muscles) (Valid <85%)
RQ at mouth doesn't always measure oxidation in cells
Use RER (respiratory exchange ratio)
● Hyperventilation - excess CO2 produced (not metabolically derived), little change in VO2
-> RER -> 1
● Lactic Acid accumulation - during high intensity exercise - increased buffering with
bicarbonate, CO2 produced -> RER -> 1
Calculating whole body CHO and Fat oxidation
Formulas
Glucose: RQ= 6CO2/6O2 = 1
Fatty acids: RQ= 16CO2/23CO2 = 0l7
Measuring the fuels we use during exercise
Aims:
Different methods to investigate fuel metabolism
Advantages and Disadvantages
If we can quantify fuel utilisation we can apply this to optimise nutritional strategies and
training interventions for health and optimal performance
Contribution of each fuel source to EE is dependant on many factors
Intensity + Duration are two main
Gender
Training status
Nutrition
Whole body substrate use
How do we measure substrate oxidation in individuals?
Indirect calorimetry - Douglas bags (gold standard), metabolic cart, respiration chamber (rare
+ very expensive) stay in for 24/48/72hrs and measure expenditure after eating or whilst
sleeping etc.
RQ=CO2/02
Use this to calculate proportion of energy from carbs and fats/contribution of the two
If Glucose RQ=1 then 100% of energy is coming from CHO
If Fatty acids RQ=0.7 then 100% of energy is coming from fats
Usually somewhere in between
What does RQ represent?
O2 and CO2 exchange representative of combustion processes occurring in oxidative tissues
(e.g. muscles) (Valid <85%)
RQ at mouth doesn't always measure oxidation in cells
Use RER (respiratory exchange ratio)
● Hyperventilation - excess CO2 produced (not metabolically derived), little change in VO2
-> RER -> 1
● Lactic Acid accumulation - during high intensity exercise - increased buffering with
bicarbonate, CO2 produced -> RER -> 1
Calculating whole body CHO and Fat oxidation
Formulas
Glucose: RQ= 6CO2/6O2 = 1
Fatty acids: RQ= 16CO2/23CO2 = 0l7
