Strain transmission along myofascial meridians might explain referred pain and offer a rationale for the development of more body-wide holistic approaches.
There is a very simple exercise you can do to illustrate the continuity in the Superficial Back Line myofascial chain between gastrocnemius and hamstrings.
The authors concluded that low back pain may cause activation of the low back musculature elsewhere along the Superficial Back Line Myofascial Continuity.
The connection between the hamstrings and the sacroiliac joint is through what is known as the superficial back line myofascial meridian/anatomy train. If the hamstrings are tight, their tension pulling force will be exerted through the sacrotuberous ligament and onto the sacrum.