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Human Energy Systems NFSC 303
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You will not be required to do the mathematical conversions from one for of energy to another (p. 83-85 of textbook)
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Energy Balance = “energy in” vs. “energy out” Energy in: Energy out:
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How do we measure Calories? Direct Calorimetry: –In food: –In humans: Indirect Calorimetry: – Newer: IDEEA device –Intelligent Device for Energy Expenditure and Activity –Records body motions every second for 24 hours.
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Components of Energy Expenditure Energy to support basal metabolism: BEE Energy to support physical activity: TEE Energy to process food: TEF
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Energy to Support Basal Metabolism BEE = Basal Energy Expenditure (Calculated from BMR = Basal Metabolic Rate) – –Measured in standard state (no food/exercise for 12 hours; measurement taken right after waking, resting at a comfortable temperature) –REE/RMR = Resting Energy Expenditure or Resting Metabolic Rate: similar numbers (not standard state)
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Primary factors affecting BMR/BEE: – – Other factors: growth, fever, ambient temp., pregnancy, smoking, disease, age, BSA, kcalorie intake –
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To estimate BEE: 1.Rough estimate: Body weight in pounds X 10 2.More accurate: Men: Women: Example:
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Energy to Support Physical Activity TEE = Thermic Effect of Exercise
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Energy Needed to Process Food TEF = Thermic Effect of Food
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BEE TEF TEE Total Daily Energy Expenditure (kcals) Remember: BMR is measured 12 hours after any physical exercise and in a fasted state.
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Wide difference in metabolic rates due to genetics... But within our individual range… –lowest would be achieved via –highest would be achieved with
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Fueling Activity
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Exogenous fuels: from outside the body –dietary protein, CHO, and fat Endogenous Fuels: from within the body – – – importance increases in times of inadequate kcalories or CHO intake
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Energy Metabolism: All processes involved in the production, storage, and use of energy As macronutrients are broken down, E from the breakage of bonds is: – – –
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ATP: Adenosine Triphosphate A-P~P~P High-energy bonds “store” energy Cleaved to release E for – – A-P~P / P = ADP A-P/ P = AMP To regenerate ATP, we need a source of P with high energy bonds: –ADP + P –AMP + 2P These high-energy bonds will come from:
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Phosphocreatine: PCr High-E molecule - helps maintain a steady supply of ATP for short bursts of energy – – – To keep regenerating ATP: –
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Metabolic Pathways Take place in the cytosol and mitochondria of the cell
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Anabolic Pathways: – – – Catabolic Pathways: – – – Anaerobic: Aerobic:
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Overview of Pathways
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Anaerobic Metabolism: Glycolysis ONLY carbohydrate can do it.
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Anaerobic Metabolism: Glycolysis Glucose (from glycogen) is “split” for E –It is only partially metabolized – will need oxygen to metabolize it completely. Primary source of E during _____________ (when O 2 availability is low) Takes place in the cytosol of the cell
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Aerobic Metabolism: Krebs Cycle and Electron Transport System (ETS) Can metabolize fat, carbohydrate (finish the job) and some protein.
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So to fuel activity, we need ATP. ATP is generated by metabolizing our fuel sources: carbohydrate, fat, and some protein. So how much of each fuel do we use during exercise? (What’s the fuel mix for a given exercise?)
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Primary Exercise Fuels: CHO and FAT Carbohydrate from ______________ Fat from ________________ Remember: only CHO can be burned when oxygen availability is low
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Fuel sources used during exercise Depend on: Intensity of activity Duration of activity Fitness level of the individual Macronutrient and kcalorie content of diet
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Fuel Sources: –Immediate – ATP/PCr system –Anaerobic – O 2 not required. Glycolysis alone can support muscle contraction for ~ 30 seconds to 2 minutes. –Aerobic – O 2 required
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When Exercise Begins… O 2 hasn’t gotten to muscles yet ATP/CP during first seconds Mostly Anaerobic for several minutes Then, aerobic (along with anaerobic) for the rest of exercise time.
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Fuel sources used during exercise Depend on: Intensity of activity Duration of activity Fitness level of the individual Macronutrient and kcalorie content of diet
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Exercise Intensity VO 2 Max THR range RPE Mild Intensity Exercise (walking) ____________________ are the predominant fuel for ATP production (Krebs and ETS) (~60% FA and 40% CHO)
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Moderate Intensity Exercise (ie. Jogging, aerobics) – – –Rely on –Therefore, more _________ is used (e.g. ~50% CHO/50% Fat) –The longer the duration, the greater use of ___________ as fuel –(for exercise lasting several hours, 60-70% energy can be supplied by fat).
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High Intensity Exercise (Strenuous, Intense) –induces ________________state in muscle cell – –Glycolysis can’t be maintained… very intense ex. only lasts seconds to minutes
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Fuel sources used during exercise Depend on: Intensity of activity Duration of activity Fitness level of the individual Macronutrient and kcalorie content of diet
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Exercise Duration TIME CHO FAT rest
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Fuel sources used during exercise Depend on: Intensity of activity Duration of activity Fitness level of the individual Macronutrient and kcalorie content of diet
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Fitness Status Increased fitness status: Increased: – –
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Training Effects of Aerobic Exercise: –– –– – LDL (“bad”)cholesterol, HDL (“good”)cholesterol –strengthened heart, lungs –curbed appetite – metabolic rate…
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Effects of Strength Training –– –– –– – LDL (“bad”) cholesterol – constipation, diverticulosis, hemorrhoids, and poss. Colon CA speeds waste through colon –stronger bones
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Fuel sources used during exercise Depend on: Intensity of activity Duration of activity Fitness level of the individual Macronutrient and kcalorie content of diet
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Diet High fat diet – Lower fat, mod. prot, high CHO diet – –
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Fatigue The inability to continue exercising at a desired level of intensity Inability to produce ATP to meet demands Other factors We’ll address fatigue in later sections.
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