Giordano S B, Segal R L
Program in Neuroscience, Emory University, Atlanta, GA 30322, USA.
Cells Tissues Organs. 2006;184(1):42-51. doi: 10.1159/000096950.
BACKGROUND/AIMS: The purpose of this study was to investigate the differential activity between and within individual muscles commonly grouped as plantarflexors. Much of the previous information gathered on plantarflexor activity has been attained using electromyographic recordings. In this study, we used magnetic resonance imaging which allowed us to look at spatial differences in activation.
Twenty-two human subjects exercised under four different conditions - combinations of loads of 25 or 65% of maximum voluntary contraction (MVC) and the direction of plantarflexion at a sagittal and off-sagittal angle. Before and after each exercise condition, T2-weighted magnetic resonance images were collected. Regions of interest were drawn around the lateral gastrocnemius (LG), medial gastrocnemius (MG), soleus (SOL), peroneus longus (PER) and tibialis anterior (TA) muscles and analyzed for differences.
Significant increases in T2 relaxation times during 25% MVC conditions were found for PER and, during the 65% MVC, for all four muscles considered plantarflexors (LG, MG, SOL, PER). No significant differences were found between sagittal and off-sagittal conditions. Within LG and MG, greater increases in T2 times with exercise were found in proximal regions compared with distal regions.
These results are consistent with suggestions that individual members of muscle groups are capable of differential activity and that for at least some muscles, such differential activity may exist within subvolumes of individual muscles.
背景/目的：本研究旨在调查通常归为跖屈肌的各肌肉之间以及个体肌肉内部的差异活动。此前收集的关于跖屈肌活动的许多信息是通过肌电图记录获得的。在本研究中，我们使用磁共振成像，这使我们能够观察激活的空间差异。
22名人类受试者在四种不同条件下进行锻炼——最大自主收缩（MVC）的25%或65%负荷与矢状面和非矢状面跖屈方向的组合。在每种锻炼条件前后，收集T2加权磁共振图像。在腓骨外侧肌（LG）、腓骨内侧肌（MG）、比目鱼肌（SOL）、腓骨长肌（PER）和胫骨前肌（TA）周围绘制感兴趣区域，并分析差异。
在25%MVC条件下，PER的T2弛豫时间显著增加，在65%MVC条件下，所有被视为跖屈肌的四块肌肉（LG、MG、SOL、PER）的T2弛豫时间均显著增加。矢状面和非矢状面条件之间未发现显著差异。在LG和MG内，与远端区域相比，近端区域随着运动T2时间增加得更多。
这些结果与以下观点一致，即肌肉群中的个体成员能够进行差异活动，并且至少对于某些肌肉，这种差异活动可能存在于个体肌肉的亚体积内。
