• Ryuta Kinugasa, Yasuo Kawakami, and Tetsuo Fukunaga.
• Research Center of Sports Sciences, Musashino University, Nishitokyo, Tokyo, Japan. kinugasa@musashino-u.ac.jp
• J Magn Reson Imaging. 2006 Dec 1; 24 (6): 1420-5.

PurposeTo use muscle functional MRI (mfMRI) to compare activation levels within and among triceps surae (TS) muscles.Materials And MethodsSeven healthy males performed five sets of 10 repetitions of a unilateral heel-raise exercise. T2-weighted images were obtained before and immediately after the exercise. Pixels that showed T2 greater than the mean +1 SD of the region of interest (ROI) in pre-exercise images and lower than the mean +1 SD of the ROI in post-exercise images were identified. The remaining T2 values in the post-exercise images were assigned to five categories indicated by color: red (highest level of activation), yellow, green, sky blue, and blue (lowest level of activation). The images were then used to construct three-dimensional (3D) images from which the volumes at each level of activation were determined.ResultsWithin each of the TS muscles the % activated volumes with low and moderate levels of activation were larger than those with a high level of activation (P < 0.05). The % activated volumes with a high level of activation were larger in the medial gastrocnemius than the soleus (Sol; P < 0.05). The Sol had a larger % activated volume with a low level of activation than the lateral gastrocnemius (P < 0.05). Each activation level was nonuniformly distributed along the length within each TS muscle.ConclusionThere is substantial variation in the level of activation within and among the TS muscles; however, the activation level is mainly in the moderate to low range in all three muscles.(c) 2006 Wiley-Liss, Inc.

25 keywords...

hide…