I once heard someone tell a patient during treatment about how careful they had to be, or they could rip the persons fascia.
I was speechless.
As impossible as that sounds (well, because it is impossible) there obviously seems to be some belief out there that the force used during a treatment could do this kind of harm (I don’t know where the therapist learned they were capable of this, so can only assume it was learned somewhere).
I also remember learning in college that when you’re working with athletes you did not want to work on them or stretch them before competition because you could lengthen their muscles and mess up their stride.
Just recently I read another article encouraging runners to use massage therapy to lengthen their muscles.
Well if we know it is impossible to apply enough force to rip fascia with our hands while doing manual therapy, is it actually possible to apply enough force to actually lengthen a muscle?
Do Muscles Lengthen?
First off it’s probably most important to understand the affect we are having on the muscle to understand whether it would actually lengthen.
When we are applying pressure to specific areas of the body, it seems we aren’t going as deep as we think we are (or at least as deep as I thought we were going).
While this study was directed at spinal manipulations for chiropractors, it shows that the friction between the skin and underlying fascia in the thoracic spine was negligible. Or in other words, when we are applying pressure to an area we aren’t getting down to the level of hitting muscle.
However, what we are doing is affecting the nervous system.
Alice Sanvito has a great article, explaining what is happening when we massage people and explains it much better than I would be able to. You can read it here.
Essentially when we are giving a massage, mechanoreceptors in the skin are sending a message via the nervous system to the brain. The brain then sends out a signal and allows change in the area to happen (that’s the quick simplified version).
In order to have an affect that could lengthen a muscle, the pressure would have to be significant. One study showed that in order to cause change to an 18mm segment at the distal end of the IT band, forces would have to be in the range of 25-67kg of force, and at this point the force would cause damage.
This is the kind of force a chiropractor is using when doing a grade five manipulation.
More importantly (as the same study showed) we aren’t specific enough in a treatment to be able to cause this kind of change. Our force is distributed through a much wider surface (ie: palm of the hand, elbow, forearm etc) and effects more of a region or a muscle group, not just one specific area of a single muscle.
Since we know when delivering a massage, we are affecting the nervous system there is no way for us to be specific enough to affect just one nerve. It would always be a bundle of nerves which again would be too broad to say we are lengthening on specific area.
Another study actually did the math to determine what kind of force it would take to change or lengthen fascia and determined, to even produce 1% change requires forces outside of human physiological range.
Animal studies have shown that stretching can cause tissue to change, but only when immobilized or placed in the stretch position for extended periods of time (days or weeks). Clearly not for the duration of a couple of minutes during a massage therapy session.
So when we feel a change when working on a patient, those changes are more likely to be a result of a change in sensation for our patients.
Length Tension Relationship And Extensibility
This is what we should be communicating to our patients.
Length Tension Relationship can be defined as:
This is where we could possibly be making a change.
Our muscles have a resting length and this is where the muscle can develop the most tension. When the muscle gets stretched manually or massaged, the tension can change (at the level of the sarcomere).
As we discussed earlier, when the brain gets a signal from the application of massage it can decrease the tension in the muscle.
But our muscles also have extensibility, which means they can be stretched to that resting length and a bit further, which is where a decrease in tension and strength would occur.
For example, if you’re doing a contract-relax stretch on a patients knee flexion you will probably feel more force from them at 45° than at 100°.
However the muscle did not actually increase in length, its extensibility is just allowing it to go past the resting length a few more degrees. And most of this is just temporary because of the fact it is predominantly a change in sensation. So at no time are we actually “lengthening” a muscle. But because of our effect on the nervous system, the altered sensation can change its length tension relationship and maybe a bit more of its extensibility. It is important for us to be able to explain things like this to our patients (maybe not down to a scientific level) so they understand exactly what we are doing to help them. Especially when a runner has been told to get a massage to lengthen their muscles.