School of Biomedical Engineering, ShanghaiTech University, Shanghai, China.
Central Research Institute, Shanghai United Imaging Healthcare Co., Ltd., Shanghai, China.
Physiol Rep. 2024 Aug;12(15):e16171. doi: 10.14814/phy2.16171.
Total amount of creatine (Cr) and phosphocreatine, or total creatine (tCr), may have a significant impact on the performance of skeletal muscles. In sports such as bodybuilding, it is popular to take Cr supplements to maintain tCr level. However, no study has explored the quantitative relationship between exercise intensity and the induced change in muscle's tCr. In this well-controlled study, straight-leg plantar flexion with specific load and duration was performed by 10 healthy subjects inside an MRI scanner, immediately followed by H MR spectroscopy (MRS) for measuring tCr concentration in gastrocnemius. For repeatability assessment, the experiment was repeated for each subject on two different days. Across all the subjects, baseline tCr was 46.6 ± 2.4 mM, ranging from 40.6 to 50.1 mM; with exercise, tCr significantly decreased by 10.9% ± 1.0% with 6-lb load and 21.0% ± 1.3% with 12-lb load (p < 0.0001). Between two different days, baseline tCr, percentage decrease induced by exercise with a 6-lb and 12-lb load differed by 2.2% ± 2.3%, 11.7% ± 6.0% and 4.9% ± 3.2%, respectively. In conclusion, the proposed protocol of controlled exercise stimulation and MRS acquisition can reproducibly monitor tCr level and its exercise-induced change in skeletal muscles. The measured tCr level is sensitive to exercise intensity, so can be used to quantitatively assess muscle performance or fatigue.
肌酸（Cr）和磷酸肌酸总量或总肌酸（tCr）可能对骨骼肌的性能有重大影响。在健美等运动中，人们普遍服用肌酸补充剂来维持 tCr 水平。然而，尚无研究探讨运动强度与肌肉 tCr 诱导变化之间的定量关系。在这项精心控制的研究中，10 名健康受试者在 MRI 扫描仪内进行了特定负荷和持续时间的直腿跖屈运动，随后立即进行 H 磁共振波谱（MRS）测量比目鱼肌的 tCr 浓度。为了评估重复性，每个受试者在两天的不同时间重复进行实验。在所有受试者中，基线 tCr 为 46.6±2.4mM，范围为 40.6 至 50.1mM；运动后，6 磅负荷时 tCr 显著降低 10.9%±1.0%，12 磅负荷时 tCr 显著降低 21.0%±1.3%（p<0.0001）。在两天的不同时间内，基线 tCr、6 磅和 12 磅负荷运动引起的 tCr 降低百分比分别相差 2.2%±2.3%、11.7%±6.0%和 4.9%±3.2%。总之，该方案可以重复性地监测骨骼肌中的 tCr 水平及其运动诱导变化。测量的 tCr 水平对运动强度敏感，因此可用于定量评估肌肉性能或疲劳。
