The science behind the HVLA thrust

The high-velocity, low-amplitude (HVLA) thrust is one of the fundamental techniques taught in chiropractic school.

DCs almost certainly understand how to perform an HVLA adjustment and how it can benefit patients, but they may not have explored the mechanics that determine how an HVLA thrust actually works. An exploration shows that HVLA spinal manipulation is rooted in some basic principles of physics.

Force, mass, and acceleration

Three laws of motion govern how objects move in relation to each other. Of these, one of the best known is expressed by looking at the amount of stress (or thrust) needed over a given area to produce a certain amount of force. The well-known equation F = MA neatly expresses this idea, in which F = force, M = mass, and A = acceleration.

Using physics in chiropractic care

How is this equation expressed within chiropractic care? Quite simply, it means that the amount of force needed to adjust a joint is equal to the area covered to move the joint, multiplied by the speed needed to do so. An adjustment can provide more force if it is concentrated over a smaller area of the body. In other words, this is what happens during an HVLA adjustment.¹

HVLA techniques

HVLA manipulation is the best-known of the various chiropractic adjustments, but there are several HVLA techniques that can be used.²

Diversified technique: This is most commonly associated with manual adjustments. A short, quick thrust is applied over the affected joint to move it back into the proper position. Its purpose is to restore full range of motion.

Thompson drop technique: This treatment uses tables hinged into various segments that can be raised or lowered. When the HVLA thrust is delivered, a particular section of the table will drop a short distance. This allows the force of gravity to help maneuver the joint into its proper alignment.

Gonstead technique: Although the HVLA adjustment in this technique is similar to the Diversified method, there are some differences in terms of diagnosing and evaluating the joints that are causing problems. Specially designed tables may be used to properly position the patient for the adjustment.

Research results

A number of individual case reports that show the benefits of HVLA adjustments, but it can be difficult to determine the effectiveness from only one or two patients. In such cases, a meta-analysis can be useful, as it will group together papers on a particular topic to determine any commonalities across the findings. This adds strength to the results.

A paper published in 2012 conducted a meta-analysis on 38 papers to determine patient outcomes of spinal manipulation for low-back pain.³ Although each study was small in terms of the number of patients, the authors concluded: “This review shows a small but consistent treatment effect at least as large as that seen in other conservative methods of care.” In other words, HVLA adjustments can be considered viable conservative care for low-back pain.

References

¹ Beychok, T. “Instrument adjusting vs. manual adjusting, part 1: The physics.” Chiropractic Economics. Published May 8, 2015. Accessed May 9, 2015.

² Spine-health. “Spinal manipulation: High-velocity low-amplitude (HVLA).” http://www.spine-health.com/treatment/chiropractic/spinal-manipulation-high-velocity-low-amplitude-hvla. Spine-health. Published July 19, 2013. Accessed May 9, 2015.

³ Goertz CM, Pohlman KA, Vining RD, Brantingham JW, Long CR. Patient-centered outcomes of high-velocity, low-amplitude spinal manipulation for low back pain: a systematic review. J Electromyogr Kinesiol. 2012;22(5):670-91.