There’s one style of treatment that chiropractors are most known for: HVLA  — high velocity, low amplitude chiropractic adjustments.

These are the adjustments most likely (though not always) to cause a popping noise (technically we call it “cavitation.”)

I don’t love the term “HVLA,” since describing the method as “high velocity” makes it sound a lot more violent and possibly dangerous than it actually is. HVLA is actually one of the safest interventions around, with the least risk of negative effects, orders of magnitude lower than, for example, taking NSAID’s.

Nonetheless, HVLA is the common term for the method many chiropractors use the most. For many chiropractors, HVLA adjustments are the main (or even the sole) element of treatment. To those chiropractors, any other methodology is secondary to or supportive of the chiropractic adjustment.

That’s not how I conceptualize chiropractic. I use a lot of different methods, and I don’t think that one method is “privileged” over any other. I don’t use HVLA adjustments with every patient. But these methods are a common element of my treatments.

Research on manual therapy methods is burgeoning (it’s about time!)

In the dark ages (ten or more years ago?), a primary focus of research was whether adjustments, manipulation, or manual therapy in general was effective at relieving pain, improving mobility, or whatever. Every flavor of hands-on treatment was lumped together in an undifferentiated mass, and all sorts of treatment outcomes were scrutinized too.

Now, spinal manual therapy in general has been accepted as an effective and safe first-line treatment for various types of spinal pain. So scientists are asking more detailed questions about the specific effects of specific types of manual therapy, including high velocity, low amplitude (HVLA) adjustments.

I recently read two review articles about the effects of HVLA.  One covered the changes in the biomechanical performance of the joints, and the other the changes in the nervous system and the way it controls movement. In both the biomechanical and neuromotor arenas, chiropractic-style adjustments were found to have effects distinct from those of other types of manipulation and manual therapy.

Proven biomechanical effects of adjustments include improved range of motion of the spine. And, after an adjustment, MRI’s showed increased “gapping” of the joints of the low back, reflecting an increase in joint space and joint mobility.

In the neuromotor arena, adjustments caused positive changes in EMG recordings (electrical recordings of muscle activity), muscle strength, the feedback from muscle sensory receptors, and even changes in brain activity (EEG tracings and motor-evoked potentials — the signals in the brain that accompany movement commands.)

What makes HVLA adjustments distinct from other forms of manual therapy?

There are two main models that try to account for the uniqueness of HVLA chiropractic adjustments within the universe of all forms of hands-on therapy.

Some scientists focus on the speed of the motion, and have discovered sensory receptors in the spinal joints that only fire when the ligaments surrounding the joint are stretched at a rapid velocity — a quickness of stretch that doesn’t occur during voluntary movement. These scientists theorize that stimulating these receptors creates novel input to the brain with beneficial results.

Other scientists point to the occurrence of cavitation as the key. Cavitation is the opening up of the joint space, often accompanied by a popping noise. When cavitation occurs, there’s more space between the two bones forming the joint, so joint motion is more free. The extra bonus you get from HVLA adjustments is that the improvement lasts for many minutes because it takes a while for the blood gases that rush into the newly-formed cavity to be reabsorbed again. This means that the treatment effect of the adjustment is prolonged.

As we continue to learn more about the direct and indirect benefits that stem from chiropractic adjustments, I’ll continue to refine my approach to take advantage of new knowledge. I’m deeply grateful that through my training and experience I’ve developed expertise in HVLA adjustments and seen first-hand how effective they can be.

Dr. Lavine has been an innovator in the use of movement and touch to promote health since 1981. He practices in New York City and Princeton, NJ.