Objectives: 

We have shown that the mechanical characteristics of bi-articular muscle is important to manage the complex, multi-joint movement, and its alteration changes the dynamic performance (Kinugasa et al. 2008, Yamauchi et al. 2007). The purpose of this study was to investigate water diffsion after different length of muscle contractions in bi-articular muscle, using diffusion-weighted MRI.

Materials: 

Seven healthy subects volunteered for this study and they were examined a lower leg before and immediately after the plantar flexion exercise on a GE 1.5 Tesla MRI scanner with a quadrature knee coil. By using diffusion-weighted MRI techniques, the apparent diffusion coefficient (ADC) value of soleus (SOL), lateral gastrocnemius (LG), medial gastrocnemius (MG) muscles was calculated. Plantar flexion exercises were performed at 20% of maximum voluntary contraction (MVC) with either 180 (KE) or 90 (KF) degrees of knee joint.

Results: 

After the exercise with KE, ADC values of LG and MG increased significantly; however, ADC values of SOL did not change significantly. On the other hand, ADC values of all muscles did not change significantly after the exercise with KF.

Conclusions: 

The higher ADC values of LG and MG after exercise with KE indicate increases in motion of intramuscular water molecules.