Magnetic resonance imaging shows that muscle myofascial force transmission causes substantial sarcomere length heterogeneity in human muscles, in vivo

Abstract

In this study, it is aimed to show, using magnetic resonance imaging (MRI), effects of epimuscular myofascial force transmission (EMFT) on sarcomere length distribution in human muscles in lower leg in vivo. The ankle angle of the subjects was fixed and 3D MR image sets were acquired for two different knee angles. Intensity based non-rigid demon algorithm was used to calculate displacement fields and Green-Lagrange strain for each voxel. To calculate the strain in local fiber direction diffusion tensor images (DTI) were acquired. It was showed that m. gastrocnemius crossing the knee has major strain distribution (0.125 ± 0.010 in proximal and 0.073 ± 0.014 distal) in local fiber direction. Despite remaining isometric during the experiment, synergistic m. soleus (e.g. 0.088 ± 0.017 in proximal, 0.078 ± 0.019 in distal) and even antagonistic muscles (0.157 ± 0.070, 0.108 ± 0.037) also show major strain distribution in the local fiber direction.