Exercise metabolism & Energy expenditure
Exercise metabolism
Substrates
Energy pathways
Rates & yields
CHO
FAT
PROTEIN
ATP-PC
Glycolytic
Oxidative
Energy expenditure
Performance
Health
Demands of exercise OR performance?
Energy expenditure > Energy intake = negative energy balance
Assess
Energy ex
Methods
Measure
Substrate metabolism efficiency
Heat production increases with energy production (Direct Calorimetry; measuring heat)
Direct calorimetry
Pros & cons
Indirect calorimetry
Indirect as it does not measure heat production
Limitations
Isotopic measurements
Isotope: element with atypical atomic weight
13C, 2H (deuterium) common isotopes for studying energy metabolism
O2 and CO2 Measurements
VO2: volume of O2 consumed per minute
VCO2: volume of CO2 produced per minute
Haldane transformation
V̇ of inspired O2 may not = V̇ of expired CO2
V̇ of inspired N2 = V̇ of expired N2
Respiratory Exchange Ratio
O2 usage to metabolize 1 molecule Fat or CHO is dependent on carbon content
O2 usage during metabolism depends on type of fuel being oxidized
Respiratory exchange ratio (RER)
RER for 1 molecule glucose = 1.0
RER for 1 molecule palmitic acid = 0.70
Predicts substrate use, kilocalories/O2 efficiency
Metabolic rate: rate of energy use by body
Based on whole-body O2 consumption (VO2) and corresponding caloric equivalent
Basal Metabolic Rate
(BMR): rate of energy expenditure at rest
Minimum energy requirement for living
Resting Metabolic Rate
(RMR)
Total daily metabolic activity
Metabolic Rate during Submaximal Exercise
Increased metabolism increases directly relative to exercise intensity
More recent evidence suggests VO2 response at higher work rates.
Prediction of BMR
Harris-Benedict (1919)
Males: 66.47+13.75(wt)+5(ht)-6.76(age)
Females: 655.1+9.56(wt)+1.85(ht)-4.68(age)
Cunningham (1980) 9.99(wt)+22(LBM)
many more, all are estimates
Predicting RMR
BW x 1.0 x 24hr – Men
BW x 0.9 x 24hr – Women
….and others.
Metabolic Equivalent (METS)
Activity Diary
Tues Night 6pm – Weds Night 6pm
Time
Activity
METs
SUMMARY/LAB
Measure RMR
Measure / Estimate Energy Expenditure
Check Activity Diaries