Recent post on motor impairment blog on passive muscle lengthening evaluated using an MRI technique call diffusion tensor imaging. They found that when passively lengthened, the medial calf showed reduction in width and depth, along with most interestingly, 8 degrees of rotation.
The rotation is intriguing, its not always considered when visualizing muscular length change. Their paper wisely notes that simple models cannot capture the complexity of the in vivo physiology. This reminds me of a previous post on our site with the rotation of the achilles into the calcaneous, with a great image from Michaud. The clinical application of taking account rotation in musculature with lengthening and the influence of that rotation on the affected joints gives us reason to consider it during kinetic chain evaluation.
I was listening the the recent gaitguys podcast where they were discussing achilles tendon bloodflow and eversion excursion, which would require of all things medial gastroc lengthening, different situation, but ties into the above study in that the DTI imaging technique might have some interesting applications on evaluating the strain happening inside our musculature.