Price T B, Gore J C
Department of Diagnostic Radiology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
J Appl Physiol (1985). 1998 Apr;84(4):1178-84. doi: 10.1152/jappl.1998.84.4.1178.
Effects of gastrocnemius glycogen (Gly) concentration on changes in transverse relaxation time (T2; ms) were studied after 5-min plantar flexion at 25% of maximum voluntary contraction (MVC). Gastrocnemius Gly, phosphorus metabolites, and T2 were measured in seven subjects by using interleaved 13C/31P magnetic resonance spectroscopy (MRS) at 4.7 T and magnetic resonance imaging (MRI; 1.5 T). After baseline MRS/MRI, subjects exercised for 5 min at 25% of MVC and were reexamined (MRS/MRI). Subjects then performed approximately 15 min of single-leg toe raises (50 +/- 2% of MVC), depleting gastrocnemius Gly by 43%. After a 1-h rest (for T2 return to baseline), subjects repeated the 5-min protocol, followed by a final MRI/MRS. After the initial 5-min protocol, T2 values increased by 5.9 +/- 0.8 ms (29.9 +/- 0.4 to 35.8 +/- 0.6 ms), whereas Gly did not change significantly (70.5 +/- 6.8 to 67.6 +/- 7.4 mM). After 15 min of toe raises, gastrocnemius Gly was reduced to 40.4 +/- 5.3 mM (P </= 0. 01), recovering to 45.8 +/- 5.3 mM (P </= 0.05) during a 1-h rest. After the second 5-min bout of plantar flexion (reduced Gly at 25% of MVC), T2 values increased by 5.0 +/- 0.8 ms (30.4 to 35.4 ms), whereas muscle Gly rose to 57.6 +/- 5.3 mM. We conclude that muscle Gly concentration per se does not affect exercise-induced T2 increases in the human gastrocnemius.
在以最大自主收缩（MVC）的25%进行5分钟跖屈后，研究了腓肠肌糖原（Gly）浓度对横向弛豫时间（T2；毫秒）变化的影响。通过在4.7T下使用交错式13C/31P磁共振波谱（MRS）和磁共振成像（MRI；1.5T），对7名受试者的腓肠肌Gly、磷代谢物和T2进行了测量。在基线MRS/MRI检查后，受试者以MVC的25%进行5分钟运动，然后再次进行检查（MRS/MRI）。受试者随后进行约15分钟的单腿提踵（MVC的50±2%），使腓肠肌Gly消耗43%。在休息1小时（使T2恢复到基线）后，受试者重复5分钟的方案，随后进行最后一次MRI/MRS检查。在最初的5分钟方案后,T2值增加了5.9±0.8毫秒（从29.9±0.4毫秒增加到35.8±0.6毫秒），而Gly没有显著变化（从70.5±6.8毫摩尔降至67.6±7.4毫摩尔）。在进行15分钟提踵后，腓肠肌Gly降至40.4±5.3毫摩尔（P≤0.01），在1小时休息期间恢复到45.8±5.3毫摩尔（P≤0.05）。在第二次5分钟的跖屈运动（MVC的25%，Gly降低）后，T2值增加了5.0±0.8毫秒（从30.4毫秒增加到35.4毫秒），而肌肉Gly上升到57.6±5.3毫摩尔。我们得出结论，肌肉Gly浓度本身并不影响人体腓肠肌运动诱导的T2增加。
