Phosphagen System - Exercise Physiology PDF

Phosphagen System  Phosphagen System 2  The phosphagen system provides ATP anaerobically and is our fastest energy system.  Itis roughly twice as fast as the glycolytic and 4x as fast as...

Phosphagen System  Phosphagen System 2  The phosphagen system provides ATP anaerobically and is our fastest energy system.  Itis roughly twice as fast as the glycolytic and 4x as fast as the oxidative system at providing ATP.  Can fuel maximal intensity activity for up to 12-15 sec  Phosphagen System is made up of 2 parts: 1) Stored ATP 2) Phosphocreatine stores Fig. 6.4. McArdle et al. 2014. Exercise Physiology… LWW Phosphagen System: ATP 3 Stored ATP Cellscontain a small quantity, so they must continually resynthesize it at its rate of use The body stores only 80 to 100 g of ATP at any time under normal resting conditions By maintaining small amounts, its relative concentration changes rapidly in response to a minimal ATP decrease Lasts only 3-5 sec @ maximal intensity Fig. 2.4. Kenney et al. 2012. Physiology of Sport… Hum.Kin. Phosphagen System: PCr 4 Phosphocreatine (PCr) Also called creatinephosphate (CP) Cells store ~4-6x more PCr than ATP PCr is used to rapidly provide ATP in the presence of ADP. Energy for ATP resynthesis comes from the anaerobic splitting of a phosphate from PCr Creatine Kinase Phosphocreatine PCr + ADP Cr + ATP Phosphagen System: PCr 5  Energy for ATP resynthesis comes from the anaerobic splitting of a phosphate from PCr  PCr energy cannot be used for cellular work  PCr energy can be used to reassemble ATP  Note that this is also a coupled reaction meaning that it includes both exergonic & endergonic reactions Creatine Kinase PCr + ADP Cr + ATP Endergonic (Anabolic) ADP ATP Exergonic (Catabolic) PCr Cr  Phosphagen System: PCr 6  Note that creatine kinase (CK) is a reversible reaction Itis used to generate ATP during high-intensity activity and to regenerate PCr in recovery from exercise The direction of the reaction depends on the energy need and is directed by the Mass Action Effect. Creatine Kinase How does the PCr + ADP Cr + ATP cell determine High-intensity which exercise PCr + ADP Cr + ATP direction the CK reaction Recovery PCr + ADP Cr + ATP goes?  Phosphagen System: PCr 7  Phosphocreatine (PCr)  ProvidesATP during maximal intensity exercise until PCr is depleted (~3-12 sec of maximal exercise)  Reaches a maximum energy yield in about 10 secs Fig. 2.6. Kenney et al. 2015. Physiology of Sport… Hum.Kin Recovery for Phosphagens 8  ATP recovery utilizes oxidative phosphorylation in the electron transport chain (ETC) via the enzyme ATP synthase. Recovery: 3-5 minutes ATP synthase (in ETC)  PCr is restored by using ATP as a substrate in the creatine kinase rxn  Recovery: 8-10 min Must recover your stored ATP first, however. PCr + ADP Cr + ATP Creatine Kinase Creatine Supplementation 9  Recovery: 8-10 min  Must recover your stored ATP first, however.  How would creatine supplementation help?  You can increase your muscle [Cr], but NOT your [PCr].  Based on the Mass Action Effect, this will help recover PCr more quickly.  Supplements can help, but training is the best way to get beneficial adaptations that can improve your phosphagen system. PCr + ADP Cr + ATP Creatine Kinase Review Questions  Why is the phosphagen system the preferred energy source at the start of exercise and for very high- intensity activity? How long does it last?  Be able to identify the structure of PCr and distinguish it from creatine.  Be able to write the ATPase and CK reactions  Be able to identify the substrates and products of the CK reaction during high-intensity exercise AND during recovery from exercise.  Usethe “Mass Action Effect” to explain the CK reaction during high-intensity sprints  Understand how ATP and PCr are replenished during recovery and how long it takes.  Apply the “Mass Action Effect” to explain how creatine supplementation could be beneficial to a power athlete. Figure & Notes References 11  Kenney, Wilmore, & Costill. Physiology of Sport & Exercise, 5th Edition. Human Kinetics, 2015.  McCardle, Katch, Katch. Exercise Physiology: Nutrition, Energy, and Human Performance, 8th Edition. Wolters Kluwer Health, 2015.