Technology gets better and better, and accordingly research continues to evolve.
There was recently an article published in which a scientist stated that 50 years ago, there were 100 scientific truths that were set in stone. Since then, all 100 of them have been disproven.
But that doesn’t mean research shouldn’t be trusted. It does mean that research methods advance, and that is why it is important to keep up to date on the literature.
As an example, for many years we thought that our instruments generated a certain amount of force and therefore that was how much force went into the body, based on research conducted in the 1990s. But current thinking shows that the prior data wasn’t quite accurate.
Back then, the first mechanical engineer had to start from scratch because no one else was doing this type of instrument research at the time. He designed a simplified test structure to measure the forces by attaching a force-measuring device to the instrument, and then firing the instrument into a steel beam.
His idea was that a steel beam was consistent in structure and thus the readings would be reproducible. This was correct insofar as the data thereby generated was reproducible, but there were some problems because the technology of that period had limitations that have only recently been overcome.
Years later, Michael Liebshner, PhD, another engineer and director of the Bio-Innovations Laboratory at Baylor College of Medicine, reevaluated the earlier research mentioned above in light of how technology has evolved.
He took one look at the test setup and determined that the forces measured earlier were incorrect for two reasons: First, the steel beam was nothing like biological tissue; therefore it was poor test material. Second, the force- measuring device needed to be attached behind the testing material to measure how much force was actually being transmitted into the body.
With his ongoing research at Baylor, Liebschner was already testing and measuring forces put into the body. He had access to improved technology, including a new testing material made from homogenous polymer blocks.
These blocks, called tissue analogs, more accurately mimic the pliability of biological tissue than the steel beam used previously.
Liebschner designed a new testing setup that more accurately measures the force transmitted into the body.1 He did this by placing one force measuring device on the instrument itself, and a second measuring device behind the test material (see picture above).
He also used several different tissue analogs as testing material to represent both flexible and rigid human spines.1 As you can surmise, better technology
and research methods allow for more accurate measurements of the force of adjusting instruments.
Another example of technology getting better and research methods evolving recently came out of the Palmer Center for Chiropractic Research. Joel Pickar, DC, PhD; William Reed, DC, PhD; and their colleagues have developed a way to measure the neural responses to different preloaded forces during a manipulation.
Their first hypothesis was that increasing the preload force magnitude would increase the neural response.
However, they found that was not supported. Instead, a smaller preload force unexpectedly evoked a significantly greater neural response than a larger one. Now, with better technology and research methods, there are answers as to why. That’s what makes better technology so promising in this area of research.
Interestingly, this finding regarding preload force applies to both manual- thrust and instrument-assisted manipulation. In fact, in the article, the authors conclude that, “Preload characteristics should be taken into consideration when judging this intervention’s therapeutic benefit in both clinical efficacy studies and in clinical practice.”2
In the clinical world, chiropractors all want definite answers, but you must remember that research and scientific instrumentation are always evolving.
Watch for trends in the literature and let good research inform your clinical decision-making.
Arlan W. Fuhr, DC, is the co- founder and CEO of Activator Methods International. A practitioner and researcher for more than 40 years, Fuhr is widely acknowledged for bringing instrument adjusting to the chiropractic profession. He can be contacted through activator.com.
1 Liebschner MA, Chun K, Kim N, Ehni B. In vitro biomechanical evaluation of single impulse and repetitive mechanical shockwave devices utilized for spinal manipulative therapy. Ann Biomed Eng. 2014;42(12):2524-36.
2 Reed WR, Long CR, Kawchuk GN, Pickar JG. Neural responses to the mechanical parameters of a high-velocity, low-amplitude spinal manipulation: effect of preload parameters. J Manipulative Physiol Ther. 2014;37(2):68-78.