McMahon Shaun, Jenkins David
School of Human Movement Studies, University of Queensland, Brisbane, Queensland, Australia.
Sports Med. 2002;32(12):761-84. doi: 10.2165/00007256-200232120-00002.
Within the skeletal muscle cell at the onset of muscular contraction, phosphocreatine (PCr) represents the most immediate reserve for the rephosphorylation of adenosine triphosphate (ATP). As a result, its concentration can be reduced to less than 30% of resting levels during intense exercise. As a fall in the level of PCr appears to adversely affect muscle contraction, and therefore power output in a subsequent bout, maximising the rate of PCr resynthesis during a brief recovery period will be of benefit to an athlete involved in activities which demand intermittent exercise. Although this resynthesis process simply involves the rephosphorylation of creatine by aerobically produced ATP (with the release of protons), it has both a fast and slow component, each proceeding at a rate that is controlled by different components of the creatine kinase equilibrium. The initial fast phase appears to proceed at a rate independent of muscle pH. Instead, its rate appears to be controlled by adenosine diphosphate (ADP) levels; either directly through its free cytosolic concentration, or indirectly, through its effect on the free energy of ATP hydrolysis. Once this fast phase of recovery is complete, there is a secondary slower phase that appears almost certainly rate-dependent on the return of the muscle cell to homeostatic intracellular pH. Given the importance of oxidative phosphorylation in this resynthesis process, those individuals with an elevated aerobic power should be able to resynthesise PCr at a more rapid rate than their sedentary counterparts. However, results from studies that have used phosphorus nuclear magnetic resonance ((31)P-NMR) spectroscopy, have been somewhat inconsistent with respect to the relationship between aerobic power and PCr recovery following intense exercise. Because of the methodological constraints that appear to have limited a number of these studies, further research in this area is warranted.
在肌肉收缩开始时，骨骼肌细胞内的磷酸肌酸（PCr）是三磷酸腺苷（ATP）再磷酸化的最直接储备。因此，在剧烈运动期间，其浓度可降至静息水平的30%以下。由于PCr水平的下降似乎会对肌肉收缩产生不利影响，进而影响随后一次运动的功率输出，因此在短暂的恢复期内最大化PCr再合成的速率将有利于参与间歇性运动的运动员。虽然这个再合成过程仅仅涉及通过有氧产生的ATP对肌酸进行再磷酸化（同时释放质子），但它有一个快速成分和一个缓慢成分，每个成分的进行速率都由肌酸激酶平衡的不同成分控制。最初的快速阶段似乎以与肌肉pH值无关的速率进行。相反，其速率似乎由二磷酸腺苷（ADP）水平控制；要么直接通过其游离胞质浓度，要么间接通过其对ATP水解自由能的影响。一旦这个快速恢复阶段完成，就会有一个次要的较慢阶段，几乎可以肯定其速率取决于肌肉细胞恢复到细胞内pH值稳态。鉴于氧化磷酸化在这个再合成过程中的重要性，有氧能力较高的个体应该能够比久坐不动的同龄人以更快的速率再合成PCr。然而，使用磷核磁共振（（31）P-NMR）光谱的研究结果在剧烈运动后有氧能力与PCr恢复之间的关系方面有些不一致。由于一些这些研究似乎受到方法学限制，因此有必要在该领域进行进一步研究。
