significantly smaller than those during diagnostic in range of motion testing." Let's think about that for a second. What they are saying is that, "In the process of giving an adjustment, we induce less force on that artery than is induced during a normal cervical range of motion study, and the strains are much smaller than the failure strains that are involved, who cause the artery to fail mechanically." Herzog and company conclude from this work that, "Cervical spinal manipulative therapy performed by trained clinicians does not appear to place undue strain on the vertebral artery and thus does not seem to be a factor in vertebral base or artery injuries." There is an important few statements in there that we need to look at. This is first of all, excuse me, my screen is just … There we go. First consideration we need to look at is that this is assuming healthy vertebral arteries. Number two, this was a laboratory study. It was not in live patients, but it was in vertebral arteries that were dissected out and removed from cadavers, the strains were tested out. There will be some criticism regarding that, that this wasn't a real world, real time, real life situation. Those same types of strain testings for all sorts of tissues, whether those tissues are arterial tissues, whether those tissues are ligamentous tissues or muscular tissues have been used throughout the history of healthcare to establish very important milestones in different disciplines. It's important for us to keep in mind. You may say, "Well, how could the strains be greater with a range of motion than with an adjustor?" It has to do … Work equals force times time. The force involved in the cervical adjustment might be … is very low, but the time is extremely low. In the consideration of the milliseconds that are involved in an adjusted thrust is generally in the range of 20 to 25 milliseconds, thousands of a second that the force is induced into the artery, in comparison to a person who has been asked to go through a range of motion study, rotate the head to the right or to the left and hold it. The time involved, the force times the time creates far greater strain over time then the milliseconds of the adjustment. It's important for us to keep that in mind. There has also been some literature over the years that has talked about patients' experience in dissections during the process of a range of motion examination. It's not an unheard of concept.
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