Both the creatine kinase and adenylate kinase reactions produce ATP, but the creatine kinase reaction has by far the greatest capacity for ATP regeneration because the CrP reserve in resting muscle is mmol kg wet weight. ATP resynthesis. Phosphorylation at the substrate level. PCr, ADP, H, → ATP, creatine. → ATP, AMP. Glycogen n a. i → glycogen n-1, It is now clear that the PCr system is fundamental to promote the rapid resynthesis of ATP, thanks to the action of CK. From the PCr, CK system, PCr acts to rephosphorylate adenosine diphosphate, ADP, to ATP between rest and exercise via the enzymatic action of Cr kinase. 49.1 PCr, ADP, The current data support the hypothesis that heat loss is lower in anaerobic ATP resynthesis than in oxidative phosphorylation and may partly explain the result. PCr reserves in skeletal muscles exceed those of ATP, moreover the catalytic capacity of creatine kinase CK is several times higher than the maximum ATP level. During high-intensity exercise, glycogenolysis is the main source of adenosine triphosphate, ATP, resynthesis coupled with creatine phosphate, PCr. Thus, a number of studies have determined the molar enthalpy of individual metabolic pathways and although the absolute values ​​differ considerably depending on ambient temperatures and experimental setting, it is consistently reported that the net degradation of creatine phosphate CP has higher efficiency than aerobic ATP resynthesis. Thus, a number of studies have determined the molar enthalpy of individual metabolisms. and although absolute values ​​differ considerably depending on ambient temperatures and experimental setting, net degradation of creatine phosphate CP is consistently reported to have higher efficiency than aerobic ATP resynthesis. The body is a complex organism and, as such, it requires energy to maintain proper functioning. Adenosine triphosphate, ATP, is the source of energy to be used and stored at the cellular level. The structure of ATP is a nucleoside triphosphate, consisting of a nitrogen base adenine, a ribose sugar, and three phosphates linked in series. The proportion of ATP derived from PCr utilization and anaerobic glycolysis depends on the duration and intensity of exercise. The peak rate of ATP delivery from PCr is greater than that of glycolysis, and during periods of contraction, breakdown of PCr contributes to ATP formation. The rate of degradation of PCr, the CP creatine phosphate system. For high-intensity, short-duration activities, ATP resynthesis must occur very quickly. As ATP stores in the muscles are depleted within the first few seconds, the CP system uses intramuscular creatine phosphate stores in the muscles to resynthesize ATP molecules, adenosine triphosphate, ATP is the only substrate that can be used directly by the skeleton. muscle to power the contraction. However, ATP stores in human skeletal muscle are relatively small, mmol kg of dry muscle and therefore must be continually resynthesized from its ADP, AMP and inorganic breakdown products,