Yanagisawa Osamu, Niitsu Mamoru, Takahashi Hideyuki, Goto Kazushige, Itai Yuji
Doctoral Program in Medical Science, University of Tsukuba, Tsukuba, Ibaraki, Japan.
Med Sci Sports Exerc. 2003 Sep;35(9):1517-23. doi: 10.1249/01.MSS.0000084418.96898.2E.
To investigate the effects of cooling human skeletal muscle after strenuous exercise using 31P MR spectroscopy and MR imaging.
14 male subjects (mean age +/- SD, 23.8 +/- 2.3 yr) were randomly assigned to the normal (N = 7) or the cooling group (N = 7). All subjects performed the ankle plantar flexion exercise (12 repetitions, 5 sets). Localized 31P-spectra were collected from the medial gastrocnemius before and after exercise (immediately, 30, 60 min, 24, 48, 96, and 168 h) to determine the ratio of inorganic phosphate to phosphocreatine (Pi/PCr) and intracellular pH. Transaxial T2-weighted MR images of the medial gastrocnemius were obtained to calculate T2 relaxation time (T2), indicative of intramuscular water level, before and after exercise (24, 48, 96, and 168 h). In addition, the muscle soreness level was assessed at the same time as 31P-spectra measurements. Fifteen-minute cold-water immersion was administered to the cooling group after exercise and initial postexercise measurements.
The control group showed significantly increased T2 from rest at 48 h after exercise (P < 0.05), but the cooling group showed no significant change in T2 throughout this study. Both groups showed a significantly decreased intracellular pH immediately after exercise (P < 0.05). After that, the cooling group showed a significantly greater value than the value at rest or the control group at 60 min after exercise (P < 0.05). For the Pi/PCr, no significant change was observed in both groups throughout this study. The muscle soreness level significantly increased immediately and at 24-48 h after exercise in both groups (P < 0.05).
The findings of this study suggest that cooling causes an increase in intracellular pH and prevents the delayed muscle edema.
使用31P磁共振波谱和磁共振成像研究剧烈运动后冷却人体骨骼肌的效果。
14名男性受试者（平均年龄±标准差，23.8±2.3岁）被随机分为正常组（N = 7）或冷却组（N = 7）。所有受试者均进行踝关节跖屈运动（12次重复，5组）。在运动前后（即刻、30、60分钟、24、48、96和168小时）从内侧腓肠肌采集局部31P波谱，以确定无机磷酸盐与磷酸肌酸的比率（Pi/PCr）和细胞内pH值。获取内侧腓肠肌的横轴位T2加权磁共振图像，以计算运动前后（24、48、96和168小时）的T2弛豫时间（T2），其指示肌肉内水分含量。此外，在进行31P波谱测量的同时评估肌肉酸痛程度。运动后及运动后初始测量后，对冷却组进行15分钟的冷水浸泡。
对照组在运动后48小时的T2较静息时显著增加（P < 0.05），但冷却组在本研究中T2无显著变化。两组在运动后即刻细胞内pH值均显著降低（P < 0.05）。此后，冷却组在运动后60分钟时的值显著高于静息时或对照组（P < 0.05）。对于Pi/PCr，两组在本研究中均未观察到显著变化。两组在运动后即刻以及24 - 48小时肌肉酸痛程度均显著增加（P < 0.05）。
本研究结果表明，冷却可导致细胞内pH值升高并预防延迟性肌肉水肿。
