Takahashi H, Inaki M, Fujimoto K, Katsuta S, Anno I, Niitsu M, Itai Y
Department of Radiology, University of Tsukuba, Ibaraki, Japan.
Eur J Appl Physiol Occup Physiol. 1995;71(5):396-404. doi: 10.1007/BF00635872.
We examined the effect of differences in exercise intensity on the time constant (tc) of phosphocreatine (PCr) resynthesis after exercise and the relationships between tc and maximal oxygen uptake (VO2max) in endurance-trained runners (n = 5) and untrained controls (n = 7) (average VO2max = 66.2 and 52.0 ml.min-1.kg-1, respectively). To measure the metabolism of the quadriceps muscle using phosphorus nuclear magnetic resonance spectroscopy, we developed a device which allowed knee extension exercise inside a magnet. All the subjects performed four types of exercise: light, moderate, severe and exhausting. The end-exercise PCr: [PCr+inorganic phosphate (P(i))] ratio decreased significantly with the increase in the exercise intensity (P < 0.01). Although there was little difference in the end-exercise pH, adenosine diphosphate concentration ([ADP]) and the lowest intracellular pH during recovery between light and moderate exercise, significant changes were found at the two higher intensities (P < 0.01). These changes for runners were smaller than those for the controls (P < 0.05). The tc remained constant after light and moderate exercise and then lengthened in proportion to the increase in intensity (P < 0.05). The runners had a lower tc at the same PCr and pH than the controls, particularly at the higher intensity (P < 0.05). There was a significant correlation between tc and [ADP] in light exercise and between tc and both end-exercise PCr and pH in severe and exhausting exercise (P < 0.05). The threshold of changes in pH and tc was a PCr: (PCr+P(i)) ratio of 0.5. There was a significant negative correlation between the VO2max and tc after all levels of exercise (P < 0.05). However, in the controls a significant correlation was found in only light and moderate exercise (P < 0.05). These findings suggest the validity of the use of tc at an end-exercise PCr: (PCr+P(i)) ratio of more than 0.5 as a stable index of muscle oxidative capacity and the correlation between local and general aerobic capacity. Moreover, endurance-trained runners are characterized by the faster PCr resynthesis at the same PCr and intracellular pH.
我们研究了运动强度差异对运动后磷酸肌酸（PCr）再合成时间常数（tc）的影响，以及耐力训练的跑步者（n = 5）和未训练的对照组（n = 7）（平均最大摄氧量分别为66.2和52.0 ml·min⁻¹·kg⁻¹）中tc与最大摄氧量（VO₂max）之间的关系。为了使用磷核磁共振波谱法测量股四头肌的代谢情况，我们研发了一种能在磁体内部进行膝关节伸展运动的装置。所有受试者都进行了四种类型的运动：轻度、中度、重度和极量运动。运动结束时PCr：[PCr + 无机磷酸盐（P(i)）]比值随着运动强度的增加而显著降低（P < 0.01）。尽管轻度和中度运动后运动结束时的pH值、二磷酸腺苷浓度（[ADP]）以及恢复过程中最低细胞内pH值差异不大，但在较高的两种强度下发现了显著变化（P < 0.01）。跑步者的这些变化比对照组小（P < 0.05）。轻度和中度运动后tc保持不变，然后随着强度增加而成比例延长（P < 0.05）。在相同的PCr和pH值下，跑步者的tc低于对照组，尤其是在较高强度时（P < 0.05）。轻度运动时tc与[ADP]之间以及重度和极量运动时tc与运动结束时的PCr和pH值之间存在显著相关性（P < 0.05）。pH值和tc变化的阈值是PCr：（PCr + P(i)）比值为0.5。所有运动水平后VO₂max与tc之间存在显著负相关（P < 0.05）。然而，在对照组中，仅在轻度和中度运动时发现显著相关性（P < 0.05）。这些发现表明，将运动结束时PCr：（PCr + P(i)）比值大于0.5时的tc用作肌肉氧化能力的稳定指标以及局部和全身有氧能力之间的相关性是有效的。此外，耐力训练的跑步者的特征是在相同的PCr和细胞内pH值下PCr再合成更快。
