Human Energy Systems NFSC 303

You will not be required to do the mathematical conversions from one for of energy to another (p of textbook)

Energy Balance = “energy in” vs. “energy out” Energy in: Energy out:

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.

Components of Energy Expenditure Energy to support basal metabolism: BEE Energy to support physical activity: TEE Energy to process food: TEF

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)

Primary factors affecting BMR/BEE: – – Other factors: growth, fever, ambient temp., pregnancy, smoking, disease, age, BSA, kcalorie intake –

To estimate BEE: 1.Rough estimate: Body weight in pounds X 10 2.More accurate: Men: Women: Example:

Energy to Support Physical Activity TEE = Thermic Effect of Exercise

Energy Needed to Process Food TEF = Thermic Effect of Food

BEE TEF TEE Total Daily Energy Expenditure (kcals) Remember: BMR is measured 12 hours after any physical exercise and in a fasted state.

Wide difference in metabolic rates due to genetics... But within our individual range… –lowest would be achieved via –highest would be achieved with

Fueling Activity

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

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: – – –

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:

Phosphocreatine: PCr High-E molecule - helps maintain a steady supply of ATP for short bursts of energy – – – To keep regenerating ATP: –

Metabolic Pathways Take place in the cytosol and mitochondria of the cell

Anabolic Pathways: – – – Catabolic Pathways: – – – Anaerobic: Aerobic:

Overview of Pathways

Anaerobic Metabolism: Glycolysis ONLY carbohydrate can do it.

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

Aerobic Metabolism: Krebs Cycle and Electron Transport System (ETS) Can metabolize fat, carbohydrate (finish the job) and some protein.

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?)

Primary Exercise Fuels: CHO and FAT Carbohydrate from ______________ Fat from ________________ Remember: only CHO can be burned when oxygen availability is low

Fuel sources used during exercise Depend on: Intensity of activity Duration of activity Fitness level of the individual Macronutrient and kcalorie content of diet

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

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.

Fuel sources used during exercise Depend on: Intensity of activity Duration of activity Fitness level of the individual Macronutrient and kcalorie content of diet

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)

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).

High Intensity Exercise (Strenuous, Intense) –induces ________________state in muscle cell – –Glycolysis can’t be maintained… very intense ex. only lasts seconds to minutes

Fuel sources used during exercise Depend on: Intensity of activity Duration of activity Fitness level of the individual Macronutrient and kcalorie content of diet

Exercise Duration TIME CHO FAT rest

Fuel sources used during exercise Depend on: Intensity of activity Duration of activity Fitness level of the individual Macronutrient and kcalorie content of diet

Fitness Status Increased fitness status: Increased: – –

Training Effects of Aerobic Exercise: –– –– –  LDL (“bad”)cholesterol,  HDL (“good”)cholesterol –strengthened heart, lungs –curbed appetite –  metabolic rate…

Effects of Strength Training –– –– –– –  LDL (“bad”) cholesterol –  constipation, diverticulosis, hemorrhoids, and poss. Colon CA speeds waste through colon –stronger bones

Fuel sources used during exercise Depend on: Intensity of activity Duration of activity Fitness level of the individual Macronutrient and kcalorie content of diet

Diet High fat diet – Lower fat, mod. prot, high CHO diet – –

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.