Energy and exercise

1. Energy and exercise • Energy of food. • Energy for bodily work. • Phosphate bond and CHO energy. • Energy for exercise. • Muscles and exercise.

2. Food energy 1 • Lipid: 9.4 kcal/g. • Carbohydrate: 4.2 kcal/g. • Protein: 5.65 kcal/g. • Lipid has 65 % potential energy > protein and 120 % > CHO.

3. Food energy 2 • Net energy value = gross energy release from direct calorimetry - energy used for digestion. • Coefficient of digestibility = % of ingested food actually digested and absorbed for metabolic needs of the body.

4. Food energy 3 • The Atwater general factors: • 4 kcal/g for CHO. • 9 kcal/g for lipid. • 4 kcal/g for protein.

5. Energy for bodily work 1 • 1st law of thermodynamics. • Energy is neither created nor destroyed, but transformed from one form to another. • Interchange between potential and kinetic energy in the body.

7. Energy for bodily work 2 • Basically, solar energy coupled with photosynthesis, powers the animal world with food and oxygen. • The process of cellular respiration is the reverse of photosynthesis.

9. Energy for bodily work 3 • 3 forms of work in human. • Mechanical: muscle action. • Chemical: synthesis of cellular molecules. • Transport: intra- and extracellular.

10. Enzymes 1 • Enzymes reduce the required activation energy. • Enzymes are usually named for the functions they perform. • Often suffix with “ase”.

12. Enzymes 2 • Hydrolysis: decomposition of complex molecules to simpler forms with the release of energy. • Condensation: simple molecules are bound together to form more complex molecules with the consumption of energy.

13. Phosphate bond energy 1 • Adenosine triphosphate (ATP) is the energy currency. • 7.3 kcal is released when 1 M of ATP is broken down to ADP. • ATP is also known as high-energy phosphate.

15. Phosphate bond energy 2 • Break down of ATP is quick and doesn’t need oxygen (anaerobic). • The body has a total of 80-100 grams of ATP. • Enough ATP for few seconds of all-out exercise.

16. Phosphate bond energy 3 • Creatine phosphate (CP) is another high-energy phosphate compound. • Storage of CP is 4-6 times > ATP. • It is known as high-energy phosphate reservoir.

17. Phosphate bond energy 4 • Phosphorylation is the process to “energise” low energy substrates (ADP and creatine) by energy transfer via phosphate bonds. • 90% of ATP synthesis is accomplished by the respiratory chain with oxidation reaction.

18. Phosphate bond energy 5 • ATP synthesis occurs when: • there is a donor of electrons; • there is an oxidising agent (oxygen) to accept the final electron and hydrogen produced; • there is enough enzymes to push the energy transfer reaction.

19. Phosphate bond energy 6 • During energy metabolism, oxygen serves as the final electron acceptor in the respiratory chain and combines with hydrogen to form water. • About 40% of the potential energy in food nutrients is transferred to ATP.

20. Energy for exercise 1 • ATP and CP stored in muscles provide immediate energy for transient and high intensity work. • Only able to support sprinting for 5-6 seconds.

21. Energy for exercise 2 • The lactic acid system. • Anaerobic glycolysis of muscle glycogen results in formation of lactic acid (LA). • Lactates are accumulated during all-out exercises. • Such exercise can last for 60-180 seconds.

22. Energy for exercise 3 • Blood lactate starts to form at 55% of maximal work capacity. • The rise in blood lactate is exponential. • Training effect.

24. Energy for exercise 4 • Long term energy. • Produced by oxidative phosphorylation. • Generally, pulmonary O2 uptake (VO2) is used to infer muscle activity.

26. Energy for exercise 5 • A plateau is reached between 3-4 minutes. • The flat portion is the steady state. • It reflects a balance between energy required by the muscles and ATP produced via aerobic metabolism.

27. Energy for exercise 6 • At the beginning of exercise, O2 uptake does not increase instantaneously. • Energy from aerobic source lags behind the actual energy needed at this stage. • The anaerobic energy sources buy time for aerobic phosphorylation.

29. Energy for exercise 7 • The difference in O2 in the initial stage is known as oxygen deficit. • Aerobic training pushes the steady state to occur more rapidly. • Maximal aerobic power or VO2max is the point where VO2 levels off despite increase in exercise intensity.

31. Energy for exercise 8 • When O2 deficit is small, steady state is reached rapidly. • Determined by the level of exercise and efficiency of aerobic energy system. • Magnitude of recovery O2 uptake (EPOC) is about the same as O2 deficit for light exercise.

32. Energy for exercise 9 • With heavy exercise, EPOC >> O2 deficit. • More time is needed for O2 uptake to return to the resting level. • Disturbance of body temperature, blood lactate, hormonal balance, etc.

34. Energy for exercise 10 • Causes of EPOC: • Resynthesis of ATP & CP. • Convert lactate to glycogen (Cori cycle). • Restore O2 to blood. • Regulate body temperature. • Regulate body physiology such as heart rate, pulmonary function, hormone levels.

35. Energy for exercise 11 • For exercise < 50% VO2max, passive recovery is more preferable. • For exercise > 60-75% VO2max, recovery is enhanced by active exercise. • Optimal recovery exercise is 29-45% VO2max for cycling, and 55-60% VO2max for running.

37. Energy for exercise 12 • Combined exercise level for recovery is no better than a single level exercise at moderate intensity. • Recovery exercise increases blood perfusion to vital organs such as liver and heart.

38. Energy for exercise 13 • Interval training. • Only uses ATP and CP system. • Repeat cycle of few seconds of all out exercise followed by a brief recovery. • Does not involve lactate accumulation.

40. Muscles and exercise 1 • Two types of muscle fibres. • Type I is the slow twitch oxidative fibre. • Type II is the fast twitch fibre, which is sub-divided into a & b. • Type IIa is fast twitch oxidative glycolytic, IIb is the fast twitch glycolytic fibre.

41. Muscles and exercise 2 • Fibre mix determines sports performance. • Genetically determined. • Training cannot change between type I and II. • Training may alter the relative % of type IIa and b.

42. Muscles and exercise 3 • Prolonged disuse affects type I more than type II fibres. • Do muscle fibres multiply themselves with training? • Is alternate aerobic/anaerobic training effective for both types of fibre?