The Bio-Chemistry of Stretch

Aches and pains in our muscles, from a Manual Therapy perspective, are viewed as our bodies protective response to unbalanced tone. Essentially our bodies are saying that for the painful activity our muscle tone is not organized in a way that will support that activity, so don’t do it. Unbalanced tone can originate from structural misalignment, or functional miss-integration, or usually both. Manual Therapy attempts to organize the structural misalignment through the use of some form of stretch. (Functional issues are addressed with some form of neuro-motor retraining ie: Feldenkrais, Masgutova.) Skillfully applied stretch techniques can better organize tone and collective muscle function involved in a specific action. The consequence of applying these techniques is obvious in improved function with less pain, however what is happening at the level of the bio-chemistry of the tissues to enable stretch has always been regarded as something of a mystery.

Here is a summary from the December 21 2012 issue of Science that tackles this subject of how individual cells can sense a mechanical input (stretch), and respond by changing their relationship to the surrounding matrix. This research compliments work on actin’s role in intracellular skeletal dynamics and to the dynamics of tensegrity [TENSEGRITY BLOG POSTS]:

CELL BIOLOGY

Feeling the Stretch

CREDIT: S. BABU ET AL., SCIENCE SIGNALING 5, 254 (11 DECEMBER 2012)

F1.mediumCertain cells in the body, particularly those of the vasculature, need to respond appropriately when they are stretched. One way they do this is through the protein zyxin. In stretched cells, zyxin is released from focal adhesions (where cells are attached to their surroundings) and goes to the nucleus, where it functions as a transcription factor to regulate gene expression. Suresh Babu et al. reveal a cellular signaling mechanism by which mechanical stretching is coupled to zyxin release. Using genetically modified mice, they found that zyxin release in response to stretching requires TRPC3 (transient receptor potential channel 3) protein, an ion channel from a family in which some members are regulated by mechanical stimuli. They showed that the channel activation appeared to cause release of endothelin-1 from mammalian endothelial cells, which then acted through its receptor to cause release of atrial natriuretic peptide, whose receptor is a guanylyl cyclase. Production of cyclic GMP (adenosine 3′-5′ monophosphate) would then activate protein kinase G, which phopshorylates zyxin, an event that appears to be necessary for its release from the focal adhesions.

Sci. Signal. 5, ra91 (2012).

The illustration shows a cell in the process of responding to a stretch signal biochemically. The red dots are some attribute of the biochemical pathway described above which has a florescent tag, and which is activating the release of focal adhesions on the periphery of the cell.

 

As a Manual Therapist, one gains a sense of these processes unfolding in tissue as one works with it. The timing of stretch response in a cell complex can vary greatly, but usually resides in the 15 second to 3 minute range. Working at a pace faster than this does not allow the tissues time to fully respond to the signal, negating the response.

NB: I should note that actually understanding this bio-chemical pathway is over my pay grade, and the pathway is presented here as evidence of the relationship between cell response and mechanical stimulation, rather than for any elucidation it might provide in and of itself.