McCully K K, Kent J A, Chance B
Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia.
Sports Med. 1988 May;5(5):312-21. doi: 10.2165/00007256-198805050-00003.
Magnetic resonance spectroscopy is a non-invasive and repeatable method of studying muscle metabolism. Magnetic resonance spectroscopy uses specific radiofrequency pulses in a strong magnetic field to determine the relative concentrations of chemical compounds in the sample. 31P Magnetic resonance spectroscopy provides indirect measures of phosphate compounds such as adenosine triphosphate (ATP), phosphocreatine and inorganic phosphate. Muscle intracellular pH can also be determined. Exercise tests can be performed in the magnet such that the metabolic response to steady-state exercise can be measured. The ratio of inorganic phosphate to phosphocreatine reflects the relative metabolic rate of mitochondrial respiration (V) and the extrapolated maximum capacity of oxidative metabolism (Vm). Normal humans vary considerably in their metabolic response to exercise. These differences are reflected in their Vms and the degree of acidosis during exercise. Active muscles in endurance trained athletes have higher Vms and faster recovery rates than normal controls. Preliminary studies have been done to assess muscle glycolytic capacity by measuring the degree of acidosis during ischaemic exercise. Exercise-induced muscle injury can be detected as an increased inorganic phosphate to phosphocreatine ratio in resting muscle. The increase in the inorganic phosphate to phosphocreatine ratio with injury reaches a peak 1 to 2 days after the injury and lasts for up to a week. Similar increases in the inorganic phosphate to phosphocreatine ratio occur in patients with destructive neuromuscular diseases. Thus changes in the resting inorganic phosphate to phosphocreatine ratio may be used to detect the degree of muscle injury following exercise. Levels of H2PO4- in muscle are thought to be important in causing muscle fatigue during exercise. As 31P magnetic resonance spectroscopy can measure H2PO4-, magnetic resonance spectroscopy has become a useful technique in the study of the metabolic causes of muscle fatigue. It may also be possible to identify the relative populations of fast twitch and slow twitch fibres in a skeletal muscle using pH changes measured with 31P magnetic resonance spectroscopy. Magnetic resonance spectroscopy using other nuclei, such as 1H, 13C and 23Na, have the potential to provide information on other metabolic changes which occur with exercise. Magnetic resonance spectroscopy has shown promise as a technique to monitor the effects of training, including overtraining, in specific muscle groups in athletes.
磁共振波谱学是一种研究肌肉代谢的非侵入性且可重复的方法。磁共振波谱学在强磁场中使用特定的射频脉冲来确定样品中化合物的相对浓度。31P磁共振波谱学提供了对磷酸化合物如三磷酸腺苷（ATP）、磷酸肌酸和无机磷酸的间接测量。肌肉细胞内pH值也可以被测定。可以在磁体中进行运动测试，从而能够测量对稳态运动的代谢反应。无机磷酸与磷酸肌酸的比值反映了线粒体呼吸的相对代谢率（V）以及氧化代谢的外推最大能力（Vm）。正常人类对运动的代谢反应差异很大。这些差异反映在他们的Vm值以及运动期间的酸中毒程度上。耐力训练运动员的活跃肌肉比正常对照组具有更高的Vm值和更快的恢复率。已经进行了初步研究，通过测量缺血运动期间的酸中毒程度来评估肌肉糖酵解能力。运动引起的肌肉损伤可以通过静息肌肉中无机磷酸与磷酸肌酸比值的增加来检测。损伤后无机磷酸与磷酸肌酸比值的增加在损伤后1至2天达到峰值，并持续长达一周。在患有破坏性神经肌肉疾病的患者中，无机磷酸与磷酸肌酸比值也会出现类似的增加。因此，静息时无机磷酸与磷酸肌酸比值的变化可用于检测运动后肌肉损伤的程度。肌肉中H2PO4-的水平被认为在运动期间引起肌肉疲劳方面很重要。由于31P磁共振波谱学可以测量H2PO4-，磁共振波谱学已成为研究肌肉疲劳代谢原因的有用技术。使用31P磁共振波谱学测量的pH变化，也有可能识别骨骼肌中快肌纤维和慢肌纤维的相对数量。使用其他原子核如1H、13C和23Na的磁共振波谱学有潜力提供关于运动时发生的其他代谢变化的信息。磁共振波谱学已显示出作为一种监测训练效果（包括过度训练）对运动员特定肌肉群影响的技术的前景。
