MRI analyses indicate non-uniform human muscle tissue deformations and confirm theoretically anticipated sarcomere length heterogeneity, in vivo

Using magnetic resonance imaging local deformations occuring within the human lower leg upon knee joint angle change have been quantified. Major deformations found are not confined to the target gastrocnemius muscle, and have been also observed within all muscles of the lower limb. Moreover, diffusion tensor imaging is used to tract gastrocnemius fibers and both lengthening and shortening deformations are found. These findings suggest that in human lower limb in vivo condition (i) myofascial force transmission occurs between muscles and (ii) sarcomere length nonuniformity occurs intramuscularly.