Schocke Michael F H, Esterhammer Regina, Arnold Winfried, Kammerlander Christian, Burtscher Martin, Fraedrich Gustav, Jaschke Werner R, Greiner Andreas
Division of Diagnostic Radiology I, Department of Radiology, Innsbruck Medical University, Anichstrasse 35, 6020 Innsbruck, Austria.
Eur J Appl Physiol. 2005 Jan;93(4):469-79. doi: 10.1007/s00421-004-1233-z. Epub 2004 Oct 29.
According to the literature the steady-state level of phosphocreatine (PCr) has a linear relationship to the workload during muscle exercise intensities below the lactate threshold, whereas this linearity is impaired during exercise intensities above the lactate threshold. The purpose of this study was to investigate the linearity between PCr kinetics and workload during two bouts of isotonic incremental calf exercise with transitions from moderate- to high-intensity as well as from high- to moderate-intensity work rates. Using a whole-body 1.5 T MR scanner and a self-built exercise bench, we performed serial phosphorus-31 magnetic resonance spectroscopy ((31)P-MRS) with a time resolution of 30 s in nine healthy male volunteers. Changes in PCr, inorganic phosphate (Pi) and pH were statistically evaluated in comparison to the baseline. The exercise protocol started with a 4.5 W interval of 6 min followed by two bouts of 1.5 W increments. The workload was increased in 2-min intervals up to 9 W during the first bout and up to 7.5 W during the second bout. The second bout was preceded by a 4.5 W interval of 2 min and followed by a 4.5 W interval of 4 min. PCr hydrolysis achieved a steady state during each increment and was highly linear to the work rate (r (2), -0.796; P <0.001). Pi accumulated during each bout, whereas the pH decreased continuously during the first bout and did not exhibit any substantial decrease during the second bout. The metabolite levels and pH were expressed as the median value and the range. Our study confirms that steady-state PCr levels also have a linear relationship to work intensities above the lactate threshold, while pH changes do not have any impact on PCr degradation. The lack of substantial changes in pH during the second exercise bout indicates that prior high-intensity exercise leads to an activation of oxidative phosphorylation.
根据文献，在低于乳酸阈值的肌肉运动强度下，磷酸肌酸（PCr）的稳态水平与工作量呈线性关系，而在高于乳酸阈值的运动强度下，这种线性关系会受到损害。本研究的目的是在两次等张递增小腿运动中，研究PCr动力学与工作量之间的线性关系，运动强度从中等强度过渡到高强度，以及从高强度过渡到中等强度。我们使用一台全身1.5T磁共振扫描仪和一个自制的运动台，对9名健康男性志愿者进行了时间分辨率为30秒的连续磷-31磁共振波谱（（31）P-MRS）检查。将PCr、无机磷酸盐（Pi）和pH值的变化与基线进行统计学评估。运动方案开始时是6分钟的4.5W间隔，然后是两次1.5W的递增。工作量以2分钟的间隔增加，第一轮增加到9W，第二轮增加到7.5W。第二轮之前是2分钟的4.5W间隔，之后是4分钟的4.5W间隔。在每次递增过程中，PCr水解达到稳态，并且与工作率高度线性相关（r（2），-0.796；P<0.001）。在每次运动过程中Pi都会积累，而在第一轮运动过程中pH值持续下降，在第二轮运动过程中没有出现任何显著下降。代谢物水平和pH值以中位数和范围表示。我们的研究证实，稳态PCr水平在高于乳酸阈值的工作强度下也与工作强度呈线性关系，而pH值变化对PCr降解没有任何影响。第二次运动过程中pH值没有显著变化，这表明先前的高强度运动导致了氧化磷酸化作用的激活。
