Human Energy Systems

1. Human Energy Systems NFSC 303

2. You will not be required to do the mathematical conversions from one for of energy to another (p. 83-85 of textbook)

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

4. 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.

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

6. 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)

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

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

9. Energy to Support Physical Activity • TEE = Thermic Effect of Exercise

10. Energy Needed to Process Food • TEF = Thermic Effect of Food

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

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

13. Fueling Activity

14. 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

15. 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:

16. 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: ATP: Adenosine Triphosphate

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

18. Metabolic Pathways • Take place in the cytosol and mitochondria of the cell

19. Anabolic Pathways: • Catabolic Pathways: • Anaerobic: • Aerobic:

20. Overview of Pathways

21. Anaerobic Metabolism: Glycolysis • ONLY carbohydrate can do it.

22. 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 O2 availability is low) • Takes place in the cytosol of the cell

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

24. 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?)

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

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

27. Fuel Sources: • Immediate – ATP/PCr system • Anaerobic – O2 not required. • Glycolysis alone can support muscle contraction for ~ 30 seconds to 2 minutes. • Aerobic – O2 required

28. When Exercise Begins… • O2 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.

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

30. Exercise Intensity • VO2Max • THR range • RPE • Mild Intensity Exercise (walking) • ____________________ are the predominant fuel for ATP production (Krebs and ETS) • (~60% FA and 40% CHO)

31. 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).

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

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

34. Exercise Duration FAT CHO rest TIME

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

36. Fitness Status • Increased fitness status: • Increased:

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

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

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

40. Diet • High fat diet • Lower fat, mod. prot, high CHO diet

41. 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.