Gycogenolysis

2. Gycogenolysis • catabolism of glycogen molecule • glycogen is polymer of glucose units • form a pin-wheel-like structure around a foundation protein, P-glycogenin • linkages at C1-C4 or some C1-C6

3. Approx. 80% of carbon for Glycolysis from glycogen, not glucose

4. Breakdown is dependant on activity of enzyme phosphorylase, hydrolyzes the C1-C4 linkages

5. Other enzyme, de-branching enzyme hydrolyzes the C1-C6 or side linkages

6. Phosphorylase is controlled by two mechanisms: • hormonally mediated: extracellular action of epi on intracellular action of cAMP (intracellular hormone) • too slow during the onset of heavy exercise • mechanism mediated by Ca2+, from the SR, parallel mechanism

7. Hormonally mediated cAMP • amplifies the local Ca2+ -- mediated process in active muscle • mobilizes glycogen in inactive muscle to provide lactate as glycogenic precursor

8. Phosphorylase is converted from phosphorylase b (inactive) to phosphorylase a (active)

9. During exercise, AMP increases, helping to minimize the conversion from phosphorylase a to b

10. RQ vs RER • both are VO2 consumed/VCO2 produced • RQ: at the cell level • RER: at the mouth

11. RQ = RER, except at the onset and offset of exercise, due to body CO2 storage changes

12. Protein RQ = 0.83

13. CHO RQ = 1.00

14. Fat RQ = 0.70

15. Anaerobic metabolism is not well understood compared to aerobic metabolism

16. Anaerobic: three misconceptions • anaerobic metabolism during exercise results in “O2 debt” • lactic acid is a “dead-end” metabolite, only formed, not removed during exercise • elevation of lactic acid levels during exercise represents anaerobiosis (O2 insufficiency)

17. Two assumptions about indirect calorimetry • ATP-PC stores are maintained, ATP comes from respiration • protein catabolism is insignificant during exercise • invalid, but necessary

18. Steady state/steady rate: • oxygen consumption is relatively constant, directly proportional to the constant submax work load

19. Rate of appearance (Ra) and Rate of disappearance (Rd) of lactate, glucose, etc. Mild to moderate intensity exercise, lot of lactate is formed High intensity exercise, more lactate is produced and appears in the blood Muscle is a consumer of lactate

20. Misconception #1) O2 consumption during exercise is insufficient to meet the demands of exercise; creating a debt

21. body “borrows” from energy reserves or credits • after exercise, pay back credits • the extra O2 consumed during recovery, above resting O2 was the O2 debt • Cease exercise: HR, breathing, etc. still elevated • B/c oxygen cost is still higher after exercise compared to rest, originally why thought is was “debt”

22. Excess Postexercise Oxygen Consumption (EPOC) • better descriptor of oxygen consumption during recovery

23. EPOC due to • Temperature • Hormones • increased energy cost of ventilation • increased energy cost of HR

24. Two phases of recovery: fast and slow

25. Much of work is based on tracer methodology: infuse radio-labeled 14C and 3H tracers

26. Misconception #2) Lactate levels lower in trained for both easy and hard exercise • lower lactate in TR concealed fact that LA production was same in TR and UNTR • TR improve lactate clearance

27. Anaerobic Threshold: • increase in intensity • oxygen consumption increases linearly • but lactate levels not change until 60% of max

28. marked inflection point, often termed “anaerobic threshold” AT, or “lactate threshold” LT • Linkages between insufficient oxygen (anaerobiosis) • lactate production • pulmonary ventilation

29. Lactic acid, HLA is strong acid: • can readily dissociate a proton (H+ ion) • HLA must be buffered: • in blood, bicarbonate (HCO3-)- carbonic acid (H2CO3) system • HLA→ H- + LA- • H+ + HCO3-→ H2CO3 • H2CO3→H2O + CO2

30. McArdle’s Syndrome: • lack enzyme phosphorylase • still demonstrate ventilatory or “anaerobic threshold”

31. Healthy young men: normally fed and glycogen-depleted • after depletion: ventilatory threshold at lower power output and blood lactate threshold at a higher power output • dissociation of Tvent and Tlact in young men after endurance training

32. Recovery • active: cool down or tapering, submaximal exercise • passive: no exercise, lie down

33. Optimal recovery from steady rate exercise • if ex. <55-60% of max, little build up of HLA • recovery: resynthesis of high energy phosphates, replenish oxygen in blood, body fluids, myoglobin, increased ventilation • recovery is more rapid with passive recovery, exercise elevate metabolism and delay return to resting

34. Optimal recovery from non-steady rate exercise • if exercise > 55-60% of max, HLA accumulation • fatigue • HLA removal from blood is accelerated by active recovery • 29-45% VO2 max is optimal for bike exercise

35. 55-60% is optimal for TM exercise • difference is probably due to localized nature of bike exercise, lower HLA accumulation

36. Active Recovery • 40 min 35% of VO2 max • 40 min 65% of VO2 max • 40 min combination: 7 min @ 65%, 33 min @ 35% • 40 min passive • which is best? why?

37. active recovery: • increases blood flow to active muscles • increases oxidation of LA • brings it to heart and liver, which have increased perfusion

38. Intermittent Exercise • decrease the LA buildup, contribution from anaerobic metabolism • can increase the capacity of aerobic system to sustain exercise at a high rate of aerobic energy transfer • if exhaustion would ensue 3-5 minutes if performed continuously, interval training would benefit

39. work to rest cycles, supramaximal exercise to overload the desired energy system • if exercise < 8 sec, intramuscular phosphates “worked” • this form of exercise has a rapid recovery, why? • will discuss this more when discuss training aerobic and anaerobic energy systems