Energy Systems for Exercise

1. Energy Systems for Exercise

2. Energy Sources • From Food: • CHO = 4 kcal • Fat = 9 kcal • Protein = 4 kcal • For Exercise: • ATP  ADP + P + energy (for muscle contraction)

3. Adenosine Triphosphate • Energy-carrying molecule found in the cells of all living things. • ATP captures chemical energy obtained from the breakdown of food molecules and releases it to fuel other cellular processes. • Cells require chemical energy for three general types of tasks: to drive metabolic reactions that would not occur automatically; to transport needed substances across membranes; and to do mechanical work, such as moving muscles.

4. Methods of Supplying ATP For Energy • Stored ATP + PC (Creatine Phosphate) or ATP-PC • Anaerobic metabolism/ glycolysis/lactic acid system • Aerobic metabolism

5. ATP-PC System • Short duration (<10 secs) anaerobic • Uses stored ATP • Strength/power movements • Replenishes rapidly

6. The ATP-PC system • Active at the beginning of all forms of activities • Especially important in high intensity exercises like weight lifting that require short bursts of energy. • The source of fuel for the ATP-PC system is ATP and PC that is stored in the muscles. Only a small quantity can be stored, so this energy source is only effective for activities that last ten seconds or less.

7. Glycolysis • Breakdown of carbohydrates for fuel • Fuel stored in the muscle as glycogen / delivered to the muscle as blood glucose • Glycolysis can produce fuel for 30 seconds to a minute for moderate heavy resistance training

8. Fast (Anaerobic) Glycolysis(The lactic acid system) • Fast glycolysis is used when oxygen is in short supply. • Fast glycolysis results in the formation of lactic acid • An increase in lactic acid in the muscle can involve muscular fatigue and ultimately cessation of exercise.

10. Active Recovery from Exercise (Cool down) • Facilitates lactate removal because of: • increased perfusion of blood through the liver and heart • increased blood flow in muscles because muscle tissue oxidizes lactate

11. Slow (Aerobic) glycolysis(The aerobic system) • Slow glycolysis is used if there is enough oxygen to allow a continuous supply of fuel. • The byproduct of this form of glycolysis is pyruvate, which is not converted to lactic acid but is transported elsewhere. • Pyruvate is eventually dissipated as sweat/urine

12. Aerobic/Oxidative System • Supplies energy to the muscle through the use of continuous oxygen transport. • System works at rest and during very low intensity exercise such as walking • This form of energy primarily utilizes fats (70%) and carbohydrates (30%) as fuel sources, but as intensity is increased there is a switch in substrate majority from fats to carbohydrates

13. Oxygen Uptake During Aerobic Exercise • Increases sharply at onset • Levels off within a few minutes if pace is constant (steady state) • Oxygen demand met by supply

14. Maximal Oxygen Uptake (VO2max) • The region where oxygen uptake plateaus and does not increase despite an additional increase in exercise intensity.

16. Oxygen Deficit • Difference between oxygen consumed during exercise and amount that would have been consumed had a steady rate, aerobic metabolism occurred at onset of exercise.

17. Order of energy production • Initial energy comes form ATP stored in muscles about 2 seconds • Then the ATP-PC system about 10 seconds • Then the Lactic acid system about 1 minute • Then the Aerobic system 1minute onwards

19. The Energy-Time Continuum • As the work time increases, the percentage of energy contributed by the aerobic system increases.

20. Blood Lactate Threshold • Exercise intensity at the point of lactate buildup. • Predicts aerobic exercise performance. • Untrained ~ 55% of VO2 max. • Trained ~ 75% of VO2 max.