HED 475 Resting and Exercise Energy ExpenditureOverviewI. Energy Metabolism: Oxygen Uptake Calculations, VO2KineticsEnergy MetabolismThe term energy metabolism refers to the sum of all the biochemical processes relating to production and use of energy. Aerobic (or oxidative) metabolism is the process of liberating energy through the breakdown of carbohydrates, fats, and proteins. The process of aerobic metabolism, which occurs in the mitochondria, involves the complete combustion of these fuels, using O2and producing CO2and H2O.There are two methods that can be used for determining the energy expenditure of a human. The most practical method is Indirect Calorimetry(which we will use in this lab). This method is based on the fact that O2is used when fuels are combusted (“burned”) and the amount of CO2that is produced by the body. An alternative, and perhaps more precise method is Direct Calorimetry. In this procedure, the subject is placed in a chamber, which measures that rate of heat production. This method is unpractical, however, due to the expense and highly sophisticated equipment required.The Respiratory Exchange RatioThe consumption of oxygen is associated with the production of carbon dioxide (CO2). Each type of fuel (carbohydrate, fat, protein) has a characteristic ratio of the volume of CO2that is produced for the volume of O2that is consumed. For example, when glucose is completely oxidized, the net chemical reaction is:C6H12O6+ 6O2——6CO2+ 6H20For glucose (and all carbohydrates) the amount of oxygen consumed (6 02) is equal to the amount of CO2(6 CO2) produced. Thus, the ratio of oxygen consumed to carbon dioxide produced is 1.0 (6/6 = 1.0). When fat is broken down, less CO2is produced per volume of O2consumed compared with carbohydrates. The ratio of CO2produced per O2consumed for “burning” only fat is 0.70.This ratio is referred to as the Respiratory Exchange Ratio (RER). By measuring VO2and VCO2, the RER can be calculated during exercise. By calculating the RER, it is possible to determine the “fuel mixture” being used during exercise.That is, it is possible to estimate the rate at which CHO and FAT are being broken down in the body. Typically the RER value is somewhere between 0.70 (pure fat) and 1.0 (pure carbohydrate), indicating a mixture of these two fuels are being used.Thebreakdown of protein contributes very little to the overall energy expenditure during exercise, and this contribution of protein is most often ignored by most exercise physiologists. Therefore, the RER that we measure in the laboratory is sometimes referred to as the “Non-Protein RER”.In order to use the RER to estimate the mixture of fuels being used during exercise, a few assumptions have to be made. First, the subject must be in steady state. This means that the
VO2and RER must not be changing during the time of measurement. Any factor that influences the production of CO2during exercise will impact the RER.The following formula is used to calculated RER:RER= VCO2/ VO2Often this is known as the respiratory quotient (RQ), however the name applies only if VO2and VCO2are measured at the tissue level. R indicates that the gases have been measured at the mouth. You can express the metabolic cost of a given task in terms of kilocalories (kcal). A kcal is the amount of heat required to raise the temperature of 1 kg of water 1ºC, and is the basic unit of all nutritional energy calculations. The following formula will compute energy expenditure:kcal/min=VO2(L/min) x kcal equivalent** kcal equivalents can be obtained from the caloric equivalents tablewhere 1 g CHO = 4 kcal, 1 g Fat = 9 kcal, 1 g protein = 4 kcalSince body weight influences the energy requirements of a given task, it is customary to correct VO2for differences in body weight.VO2(ml/kg/min)=VO2(ml/min) / body weight (kg)MethodsI. Equipment1. On-line VO2/VCO2collection system oxygen analyzer, oxygen sensor, carbon dioxide analyzer, carbon dioxide sensor, flow meter, gas meter, PC computer, hoses, facemask.2. Polar heart rate monitor3. Stationary bikeII. Subject Profile1. Height2. Weight3. AgeIII. General Procedures1. Equipment is turned-on and allowed to warm-up for at least 30 minutes2. Gas analyzers are calibrated with gases of known concentration3. Subject information is typed into the computer 4. Subject position themselves on the device (bike)5. Facemask is donned by the subject6. Collect air from subject 2 minutes prior to starting test*See Energy Metabolism lecture for the rest of the methods & data.
Data Recording SheetSubject_____________________Date___________Gender_______Age___________Height _______/_______in/cm Weight_____/______lb/kg________________________________________________________________Stage 1 Rest:12AverageHeart Rate (bpm)___________________VO2(L/min)___________________VCO2(L/min)___________________RER___________________________________________________________________________________Stage 2 125 WATTS:12AverageHeart Rate (bpm)___________________VO2(L/min)___________________VCO2(L/min)___________________RER___________________________________________________________________________________Stage 3 150 WATTS:12AverageHeart Rate (bpm)___________________VO2(L/min)___________________VCO2(L/min)___________________RER___________________________________________________________________________________Stage 4 175 WATTS:12AverageHeart Rate (bpm)___________________VO2(L/min)___________________VCO2(L/min)___________________RER___________________
Calculation of Fuel Contribution and Usage (Use as an example)VO2(L/min) ___________RER _____________Kcal/L O2consumed (from table) _______________ %CHO____________%Fat _____________Kcal/L O2consumed X VO2(L/min) = Total calories expended per minute_________ X ________ = ________________
Caloric Equivalents Tablekcal / L oxygenCalories derived from:Non-protein RconsumedCHO %Fat %0.704.6860.00100.00.714.6901.1098.90.724.7024.7695.20.734.7148.4091.60.744.72712.088.00.754.73915.684.40.764.75119.280.80.774.76422.877.20.784.77626.373.70.794.78829.970.10.804.80133.466.60.814.81336.963.10.824.82540.359.70.834.83843.856.20.844.85047.252.80.854.86250.749.30.864.875184.108.40.2064.88757.542.50.884.89960.839.20.894.91220.127.116.114.92467.532.50.914.93670.829.20.924.94818.104.22.1684.96177.422.60.944.97380.719.30.954.98584.016.00.964.99822.214.171.1245.01090.49.580.985.02293.66.370.995.03596.83.181.005.047100.00.00
Lab 1 Energy Expenditure Lab ReportAttach all data sheets, and type calculations and answers on a separate sheet. The paper will be written manuscript style, using 12-point font (Times New Roman, Times, or Arial), double-spaced.Title Page –Includes paper title, author, date, courseIntroduction–Describe why you are doing the study. Present information about what is already known about the topic. State your purpose and hypothesis.Methods–Describe the setup of the study, including the subject’s characteristics (do not use their name), measurements taken, exercise protocol, and equipment used.Results–Present the findings of the study.A.Stage 1–Use average values for the selected 2 minutes of steady-state metabolism of the collection period (given to you by the instructor)1.What percentage of carbohydrate and fat was utilized for energy (see RER Table)?2.What is the caloric equivalent for oxygen (see RER Table)?3.Calculate the rate of energy expenditure (kcal/min). 4.Based on #3, calculate the daily (24 hour) resting metabolic rate (kcal).B.Stage 2–Use average values for the selected 2 minutes of steady-state metabolism of the collection period(given to you by the instructor)1.What percentage of carbohydrate and fat was utilized for energy (see RER Table)?2.What is the caloric equivalent for oxygen (see RER Table)?3.Calculate the rate of energy expenditure (kcal/min). 4.Based on #3, how long (hrs) would the subject have to bike at this workloadto lose 1 lb of fat (3500 kcal)?C.Stage 3–Use average values for the selected 2 minutes of steady-state metabolism of the collection period(given to you by the instructor)1.What percentage of carbohydrate and fat was utilized for energy (see RER Table)?2.What is the caloric equivalent for oxygen (see RER Table)?3.Calculate the rate of energy expenditure (kcal/min). 4.Based on #3, how long (hrs) would the subject have to bike at this workloadto lose 1 lb of fat (3500 kcal)?D.Stage 4–Use average values for the selected 2 minutes of steady-state metabolism of the collection period(given to you by the instructor)1.What percentage of carbohydrate and fat was utilized for energy (see RER Table)?2.What is the caloric equivalent for oxygen (see RER Table)?3.Calculate the rate of energy expenditure (kcal/min). 4.Based on #3, how long (hrs) would the subject have to bike at this workloadto lose 1 lb of fat (3500 kcal)?
Figures–GO IN THE RESULTS SECTION Present the data in a table and/or graphically in figures.Figures –Use average values; make bar/column graphs (label “Figure 1”, etc.); interpret each of the following:1.Heart rate (bpm) on Y-axis (start Y-axis at 50) vs Stage 1/2/3/4on X-axis2.VO2(L/min) on Y-axis vs. Stage 1/2/3/4on X-axis3.RER on Y-axis (start Y-axis at 0.60) vs. Stage 1/2/3/4on X-axis4.Energy (% Fat vs. Carbohydrate) on Y-axis vs. Stage 1/2/3/4on X-axis5.Energy Expenditure (kcal/min) on Y-axis vs. Stage 1/2/3/4on X-axisDiscussion–Explain the results.Why do you think that you obtained the results that you observed? Support your findings with references.1.What energy systems are being used by the subject during each level of intensity, and to what extent? (PCr, anaerobic, aerobic)2.How does exercise intensity influence the type of substrate utilization (fat vs. carbohydrates)?3.How does intensity affect oxygen use and how do you know? Why does this happen?4.How does intensity affect caloric expenditure and how do you know? Why does this happen?5.What types of foods (fats, carbohydrates, protein) do you think would be best to ingest before, during, and after each exercise intensity, and why?References–List all references used. References should be formatted using APA style –alphabetically by author. You should haveat least 5 references, with at least 3 of them coming from peer-reviewed scientific journal articles. You may use your book as a reference
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