Summary
Dr. Dean Smith interviews Dr. Bernadette Murphy, a leading chiropractic neurophysiology researcher at the University of Ontario Institute of Technology. Dr. Murphy describes how a running injury treated by a chiropractor in Toronto inspired her career, particularly the biomechanical, root-cause approach rather than just treating inflammation. She went on to complete her PhD in human physiology at the University of Auckland, where she became fascinated by how the central nervous system processes afferent input from spinal manipulation. The conversation covers Dr. Murphy's foundational research on H-reflexes and sacroiliac joint manipulation, which provided objective neurophysiological evidence that adjustments produce measurable changes in nervous system function -- not just placebo effects. She discusses how modern techniques like somatosensory evoked potentials, EEG, and electromyography give researchers windows into the nervous system at all levels. A key insight is that the old "bone on nerve" mechanical explanation has evolved: chiropractic manipulation creates changes in afferent input that the central nervous system then processes, affecting motor control, proprioception, and sensory integration. Her work on repetitive strain injuries revealed that patients often don't perceive developing overuse until pain appears, suggesting the nervous system fails to process early warning signals.
Key Points
- Spinal manipulation creates measurable changes in nervous system function via H-reflex and somatosensory evoked potentials
- The old "bone pressing on nerve" model has been replaced by understanding how adjustments alter afferent input to the CNS
- After sacroiliac manipulation, patients report improved stride and muscle function -- now backed by objective neurophysiological data
- Modern neuroimaging techniques provide windows into brain and spinal cord responses to chiropractic adjustments
- Repetitive strain injuries develop because the nervous system fails to process early overuse signals before pain appears
- Dr. Murphy's research bridges chiropractic science and basic neuroscience, advancing understanding of how the brain processes sensory information
- It took 6 months of H-reflex practice to achieve reproducible measurements, underscoring the rigor required for quality research
- Heart rate variability changes after cervical manipulation suggest systemic autonomic nervous system effects
Key Moments
H-reflex studies provided first objective evidence that manipulation changes nervous system
Dr. Murphy's early H-reflex research provided objective neurophysiological evidence that sacroiliac joint manipulation creates measurable changes in the nervous system — something patients couldn't fake, unlike subjective strength reports.
"it's just because they were trying harder after. But if you have something objective that they can't fake and you can sort of say, yeah, this has changed, then it begins to give you both the sort of neurophysiological evidence to go then with the increased strength. And then you can start drawing conclusions about mechanisms, which A, helps us actually design better treatments and also hopefully can help us with diagnosis in some of the really tough cases. Exactly. Yeah."
Heart rate variability changes after manipulation reveal nervous system impact
Decreased heart rate variability is now understood as a marker of illness found in depression, chronic pain, and even neonatal sepsis. Research showing chiropractic can impact heart rate variability provides powerful evidence that it affects the autonomic nervous system on multiple levels.
"in Saskatchewan and I was reading the literature on chronic pain and again now they're understanding that again people in chronic pain get this decreased variability so if you now know that something is a really good marker for illness or people being not well and you're able to show that chiropractic can impact that I think that's very powerful evidence that chiropractic is able to actually affect the nervous system on many levels."
The strain is in the brain — chronic overuse rewires the sensory cortex
Research on monkeys doing repetitive tasks showed that their sensory cortex maps became smeared and disorganized, demonstrating that chronic strain causes neuroplastic changes in the brain — and explaining why chronic conditions require many visits to recalibrate the nervous system.
"It was now smeared and you got all kinds of strange activation patterns. Interesting. And so it really, for me, was the beginning of that evidence that the strain is in the brain. It's not only in the muscle. If it's gone on for long enough, and as chiropractors, it's really critical when we're trying to explain prognosis to patients that it's not just about..."
Manipulation normalizes muscle firing patterns rather than just increasing activity
TMS research reveals that spinal manipulation normalizes muscle patterns — overactive muscles become more inhibited while underactive muscles start firing more, rather than simply increasing activity across the board.
"Basically, what happens is a muscle that tends to get overactive, it will actually get less active or it'll become more inhibited, which is appropriate, whereas muscles that have become underactive in response to manipulation, they'll start firing more. Oh, so..."
