2. Energy Systems

3. All bodily functions require an energy source. The only currency that can be used at the cellular level for this is A.T.P (Adenosine tri- phosphate). We only have 50gms of ATP stored in our muscle which can only last for around 2 sec of intense activity. An adult of around 80 kg requires around 150 kg of ATP in order to provide energy at rest for 24hours. Energy Systems ATP Adenosine Triphosphate Adenosine PP P The energy for muscle contraction is derived when one of the 3 phosphate bonds is broken ATP ADP + Pi + ENERGY We end up with: Adenosine PP Pi E Note: by- product: Pi ( inorganic phosphate)

4. We cannot store such quantities so we have to resynthesise / rebuild ATP so that we can continue activity. In order to do this we must provide energy back to ADP and Pi to re-bond them. It is the metabolism / break down of fuel stored (PC) or what we consume (Carbohydrates, fats & Protein) that resynthesises ATP via 3 main energy systems. Energy Systems ADP + Pi + ENERGY ATP E A PP Pi

5. Energy is released when an electrical impulse from the motor neuron stimulates the muscle resulting in one of the three phosphate group being chemically broken down leaving A.D.P. (Adenosine Di- phosphate) and one inorganic phosphate. The energy released causes the muscle to contract by activating the myosin cross-bridges. **See e-teaching disc 1 animation Energy Systems

6. Energy is provided via 3 energy systems. 2 anaerobic and the aerobic systems. The amount and rate by which ATP is demanded and resynthesised is determined by 2 main factors:  The INTENSITY and DURATION of the activity. Energy Systems ADP + Pi + ENERGY ATP The breakdown of fuels to provide this energy are: ANAEROBIC WITHOUT O 2 AEROBIC WITH O 2 FASTSLOW ATP / PCLACTIC ACID O 2 CarbohydrateO 2 Fats FASTEST SLOWEST

7. This is the fastest system but it is also the one with the lowest capacity. It is also known as the alactacid or phosphate system. Thus it is used for: –High INTENSITY and short DURATION activities. –We previously stated ATP lasts for approximately 2 secs. –PC or CP or CrP is one in the same. It is stored in the skeletal muscle and can breakdown to provide the required energy to resynthesis ADP +Pi to ATP Energy Systems The ATP-PC System ATP ADP + P + ENERGY PC P + C + ENERGY E

8. Energy Systems –PC resyntheses ATP from 0-12 sec and peaks in it’s power output at around 3-4 sec. –It is dominant up to 6 sec in all out efforts. –Specific training can increase PC stores to allow longer duration as well as a faster rate of breakdown. (Creatine supplements may also enhance PC supplies.) The ATP-PC System The breakdown of PC does produce the by-product, Pi ( these have an influence on fatigue mechanisms)

9. Energy Systems The ATP-PC System Used for high intensity Jumps, Throws, Sprints Peak power in 3-4 sec but depleted in 10-12 secs Requires 3 minutes of passive recovery to rebuild stores Fast breakdown, so fast resynthesis of ATP Dominant over 0-6 secs..

10. If the intense activity continues on beyond the 10 sec mark it is imperative that a fast source of energy is tapped into for ATP resynthesis. remember  The INTENSITY and DURATION of the activity determine the required rate of ATP resynthesis and the amount. Energy Systems ADP + Pi + ENERGY ATP Since the PC system is exhausted the major contribution now needs to come from the next fastest builder of ATP ANAEROBIC WITHOUT O 2 FAST ATP / PC depleted Anaerobic glycolysis / lactic acid

11. This is the next fastest system and it can extend high intensity work from 6-60 sec and contribute up to 2 minutes. Thus it is used for: –High INTENSITY and medium DURATION activities. –It is also known as anaerobic glycolysis –Stored Muscle glycogen is incompletely broken down to pyruvic acid and without adequate O 2 to further break it down, it converts to Lactic acid –It can quickly breakdown to provide the required energy to resynthesis ADP + Pi back to ATP –Each glucose molecule provides enough energy to resynthesise 2 ATP’s Energy Systems The Lactic Acid System ATP ADP + P + ENERGY Glycogen Glucose (C 6 H 12 O 6 ) LA + ENERGY E

12. Energy Systems –The LA system peaks in it’s power output at around 15 sec. It is dominant up to 60 sec and can contribute in all out efforts up to 120sec. –Anaerobic glycolysis occurs in the cytoplasm (fluid environment) of the cell The Lactic Acid System The breakdown of glucose anaerobically produces the metabolic by-product, Lactic Acid (at very high intensity LA builds up in the muscle and is pushed into the blood stream where it travels as blood lactate and H + ions ) these H+ have an influence on fatigue mechanisms)

13. Energy Systems Used for high intensity 200-400m Sprints or repeated sprints without rest Peak power in 15 sec but by-products Lactate and H + Requires 1hour of recovery to remove LA Relatively fast breakdown, so fast resynthesis of ATP The Lactic Acid System Lactic acid ( H + ) lowers the muscle pH (more acidic), reducing ATP resynthesis. Dominant over 6-60 secs..

14. The Lactic acid system is used in high intensity activities above 85% max heart rate when the aerobic system is not able to fully meet the ATP demands of the activity. Anaerobic glycolysis occurs in the cytoplasm of the muscle cell and produces 2 ATP and the metabolic by-products Lactate and H+ which dissociates from lactic acid in the muscle. Energy Systems The Lactic Acid System Sports scientists study the Blood Lactate (BLa) levels of athletes as it indicates fitness levels and training effectiveness. It is far easier to measure BLa levels than the H + ion levels in the blood. These levels will remain constant when an athlete is working at an intensity that they can sustain.

15. –If an athlete exceeds this intensity, more Lactate is produced and it starts to accumulate in the blood. –This accumulation of blood lactate corresponds to the intensity / workload beyond the Lactate Inflection Point (LIP) –Lactate is not the problem as it is a rich fuel used by the heart and slow twitch muscles, it is the H + ion that is associated with lactate that causes the acidosis, impairing muscle contraction. –This tends to lower the pH due to excess H +, and if enough is added, the pH goes down far enough to affect the structure of every enzyme (enzymes push the reactions along) in the muscle cell, decreasing its function. –This causes a loss of performance or fatigue. –LIP is the region of balance between lactate appearance in the blood and its removal. Energy Systems L actate I nflection P oint

16. –Exercise intensities beyond the LIP are associated with fatigue; the greater the exercise intensity above the inflection point, the more rapid the fatigue. –This fatigue is generally considered to be a consequence of a greater reliance on anaerobic metabolism to supply the adenosine tri-phosphate (ATP) demands of the exercise task and the resultant accumulation of the by-products of anaerobic metabolism eg H + (ref.VCAA 2007 ) Energy Systems LIP LIP describes the intensity beyond which a given power output / speed can not be maintained by the athlete. (referred to as critical power or speed). Basically this means that although BLa starts to increase at LIP, you can continue to work for up to 2 hours at LIP level. If you exceed the LIP you cannot maintain the pace. LIP zone Beyond LIP Aerobic training can lead to lower BLa levels and a higher LIP for any given intensity

17. Energy Systems LIP The LIP training range varies from 60% - 90% of Max VO 2 and 65% - 90% of Max HR. Training at an intensity that is above the LIP has been shown to result in an improved performance in endurance sports compared to training at the LIP. BEYOND LIP is associated with an increase in exercise intensity resulting in:  Greater ATP demand  Increased glycolytic rate  Increased H + accumulation  Increased LA Accumulation  Inadequate ATP supplied via oxidative processes. (Kreb’s and ET)  Decreased time to exhaustion

18. This system is the largest producer of energy for ATP resynthesis ie it has the greatest capacity but at the cost of having the slowest rate of ATP production: As it implies, O 2 is used to breakdown fuels to resynthesise ATP. –Low INTENSITY and long DURATION activities. –This system can use 3 fuel supplies (CHO, FATS and PROTEIN) Energy Systems The Aerobic System Fat and carbohydrate (CHO) provide the vast majority of fuel required for energy production in skeletal muscle during all intensifies of aerobic exercise. CHO is available within the muscle fibre (in the form of glycogen) and from blood glucose (from the breakdown of liver glycogen). Fat is available from Adipose tissue, triglyceride (TG) droplets within the muscle fibre (intramuscular triglyceride, IMTG) as well as from plasma free fatty acids (FFAs) Protein is available from amino acids and is limited in it’s use in normal circumstances. (can be up to 10% in extended endurance activities)

19. Energy Systems Largest CHO stores Largest FAT stores 2 nd largest CHO stores 3rd largest CHO stores 2 nd largest FAT stores 3 rd largest FAT stores All are burnt in the mitochrondria of the muscle cell

20. The 3 fuel supplies (CHO, FATS and PROTEIN) are used in different proportions depending on the rate and capacity of ATP required. At rest we use a mix of around 2/3 fats and 1/3 CHO as the rate of ATP required is very low and we have O 2 in plentiful amounts. (fats yield more energy than CHO and Protein, 38kj/gm cf 17kj/gm, but require more O 2 as they are more complex molecules and more processes are involved in metabolising them). thus the rate is also slower than CHO As intensity and rate increases we become more reliant on CHO Energy Systems The Aerobic System For any given intensity, well trained endurance athletes can use more fats than CHO compared to the untrained. (ie glycogen sparing effect)

21. Energy Systems The Aerobic System Adipose tissue TG constitutes by far the largest energy store in the body sufficient to sustain skeletal muscle contraction for approximately 120 hours at marathon running pace! On the other hand, if only CHO were utilised as a fuel, it would deliver energy for approximately only 90 minutes of running. Thus we must use a combination of both fuels in distance events. For any given intensity, well trained endurance athletes can use more fats than CHO compared to the untrained. (glycogen sparing effect)

22. Aerobic Glycolysis: 1.Glycogen is broken down into glucose and then to pyruvic acid. This rebuilds 2 ATP 2.Pyruvic acid is further broken down and more energy is released with CO 2 produced. 3.Electron transport Chain where the most ATP is resynthesised and H 2 O and heat are produced Thus the aerobic breakdown of glucose yields 39 ATP along with heat, CO 2 and H 2 O This compares well with the anaerobic breakdown where either 2 or 3 ATP’s are resynthesised. Also this takes far more time to achieve thus the rate of ATP resynthesis is slower. Energy Systems The Aerobic System

23. STAGE 1 STAGE 2 STAGE 3 Energy Systems The Aerobic System Glycogen Glucose Pyruvic Acid + 2 ATP Pyruvic Acid KREB CYCLE ATP CO 2 ATP CO 2 H2OH2OH2OH2OATP ELECTRON TRANSPORT THESE PROCESSES ALL OCCUR IN THE PRESENCE OF O 2 WITHIN THE MITOCHRONDRIA OF THE MUSCLE FIBRE

24. Energy Systems The Aerobic System FATS (FFA) AND PROTEIN (Amino Acids) CAN ALSO ENTER AT THIS STAGE Acetyl Co-A KREB CYCLE ATP CO 2 ATP CO 2 H2OH2OH2OH2OATP ELECTRON TRANSPORT THESE PROCESSES ALL OCCUR WITHIN THE MITOCHRONDRIA OF THE MUSCLE FIBRE

25. At about the 30sec. mark of high intensity exercise the aerobic system produces ATP at the greatest rate. However, the anaerobic systems are still predominant in events up to about the 75sec. If we work at an intensity that allows all of the ATP to be supplied aerobically then we reach a situation called Steady State (heart rate, respiration rate, etc) are all constant. If we keep increasing our intensity then we keep increasing our demand for ATP. When we get to the point where we have to get greater help from the lactic acid system, LIP or critical power / speed is reached. To go beyond this intensity will place extra demand on ATP resynthesis rate and although the O 2 system is dominant H + accumulation leads to fatigue. In some circumstances muscle glycogen stores can be depleted during extended aerobic performance. The body must burn more fats (fatty acids) to produce ATP. This also has an effect on reducing blood glucose levels as fats must burn in a CHO fire! This is similar to the effects associated with Diabetes (hypoglycaemia) This is commonly referred to as ‘Hitting the Wall’ The problem is that fat requires large amounts of oxygen to burn. The athlete is unable to significantly increase their VO 2. Therefore the athlete must therefore slow intensity down dramatically. Energy Systems The Aerobic System

26. Energy Systems Interplay It is important to note that all systems are not independent. They all have their strengths and weaknesses. When demand is great for ATP, the systems that provide energy fastest are the main contributors. If this intensity continues then the next fastest dominates as the previous dwindles. All the time the O 2 system is increasing its contribution using CHO in high intensity and more fats when intensity is low and duration long.

27. Energy Systems Interplay When the exercise intensity and therefore energy demand is extremely high (Above the LIP) as is indicated above, anaerobic energy via anaerobic glycolysis provides the remaining required ATP. (supra-maximal exercise) Exercise at this intensity can only last for a relatively short time (acidosis) but the predominant system will still be the aerobic system. (The Aerobic system is the predominant system over the duration of the performance.) Notice this persons Max VO 2 is 60ml/kg/min The PC & lactic acid system is contributing the extra ATP beyond the O 2 system for this activity

28. Energy Systems Interplay

29. Energy Systems Anaerobic Power and anaerobic capacity – what’s the difference? The total amount of ATP that can be produced by any one person anaerobically is a finite capacity. ie there is only so much ATP derived from PC and the lactic acid system. (amount of ATP) This graph shows the same anaerobic capacity for 3 different events for an athlete. The remaining energy for the event is derived from the O 2 system. Anaerobic power is the maximum rate at which the anaerobic systems can produce this energy. Peak power usually occurs within the first 10 sec of effort. The 400m would produce energy at the greater rate than the other events. anaerobic power = rate of anaerobic energy production, where as; anaerobic capacity = total amount of anaerobic energy produced.

30. The balance between aerobic & anaerobic energy EXAMPLE:ANAEROBIC CAPACITY = 50 ml/kg AEROBIC POWER = 50 ml/kg/min We can see from this example as well that total energy is dependant upon the aerobic system as there is a limit to the anaerobic capacity

31. Overview Rating 1-3 1-highest ATP/PCLAO2O2 POWER /RATE INTENSITY CAPACITY/ YIELD DURATION 1 1 1 12 2 2 2 3 3 3 3