In our practice, we have been measuring HRV (heart rate variability) for a while now. This test gives us an indication of how resilient or adaptable your nervous system and body is at that time. Objective measures like this are great to track over time to see how the body is responding to any intervention. The evidence base around this technology is growing around the world, and while it is still new, it’s utilisation is increasing – not just in chiropractic, but also in medicine and sports. Here is an interview with someone who has waaaaaay more understanding in the nuts and bolts of HRV than me and I think is definitely worth the read.
A new case series published in the Chiropractic Journal of Australia has shown sustained improvement in heart rate variability in six individuals. The retrospective case series, which used the Australian Spinal Research Foundation’s conceptual definition of the Vertebral Subluxation, is an excellent example of one way we can objectively measure the impact of chiropractic care beyond short-term pain management alone. We caught up with Dr Amy Haas to chat about it.
Dr Haas’s recent case series, co-authored with our own Dr Dave Russell, chronicled six patients at varying ages and stages of life. All underwent chiropractic care focused on the detection and correction of vertebral subluxations, and all experienced varying but impressive improvements over the course of the data recording.
Why HRV (Heart Rate Variability)?
For Dr Haas, a PhD in Biochemistry and twelve-year veteran of experimental laboratory research at the Medical College of Wisconsin as well as Harvard Medical School before entering Chiropractic, the area of Heart Rate Variability (HRV) is an intriguing one. “I find the applicability of HRV to chiropractic unique and fascinating. It holds a truly a fantastic opportunity for us to really tell the story about chiropractic, adaptability and the influence of the adjustment on the function of the nervous system.”
Haas was looking for a user-friendly and intuitive way to gain insights into how her patients’ health was changing with a course of chiropractic care. Amongst the available objective outcome measures she chose to use with her patients, HRV caught her attention due to its ability to reach beyond the realms of the musculoskeletal, and show patients the power of the adjustment on physiology in a tangible and objective way.
“There are plenty of outcome indicators available to look at pain or range of motion. There are a few that are fantastic for physiology – Heart rate proper and blood pressure for example. But HRV really caught my attention because it is a window into the three arms of the safety pin cycle. It requires input, integration in the brain, and then execution of an adaptive response. In a nutshell, that’s adaptation.
Because HRV requires all three of those components, and the nervous system is the centre of integration, it presents a unique opportunity for chiropractors. One of our explanations of subluxation is the disafferentation theory where you have a disturbance in the safety pin cycle. That can be any of those three arms: inaccurate information going into the brain, inaccurate integration or execution of the response. HRV can’t distinguish between those per se but it can suggest a breakdown of that safety pin cycle.”
When it came to choosing cases to put in the retrospective case series, Dr Haas had plenty of options. All of her patients at her private practice, which specializes in correction of vertebral subluxation, get assessed for baseline physiology when they begin care, then retested at 30, 60, 90 days or at her discretion based on each individual case. HRV is part of that measurement.
“My patients love that because they want data. I work with a lot of engineers of varying types and a lot of folks with advanced degrees.” says Dr Haas. “They want to see how their health is improving in an objective way. They love the emotional component of chiropractic: the understanding that there is hope, that health can improve when vertebral subluxation is corrected, they can feel better, they can function better, they can enjoy their lives more. But they also love the logical component. If you are delivering care to increase the function of the nervous system then there should be some objective measurement showing that your care is creating the outcome intended.”
The Case Reports:
From the many potential cases, Dr Amy chose the six featured cases because of their similarities and the fact that they all met established criteria set by other HRV studies: the patients weren’t on medications, hadn’t had any lifestyle changes that would have precipitated any emotional or chemical stressors, didn’t pick up or stop an exercise program, or start taking supplements such as omega 3s. In short, very little else changed in their regular routine apart from them starting to get adjusted, minimizing the possible variables that could be responsible for health changes.
As we age, published normative research data predicts linear decrease in the SDNN* measurement for HRV. This is what makes Haas and Russell’s case series so noteworthy – instead of declining with age, baseline pre-adjustment measurements for SDNN actually increased and remained elevated over time, suggesting a reversal of the predicted decline.
The six cases were comprised of three male and three female patients of varying ages. All patients were managed using Diversified and Thompson Terminal Point Techniques (TTPT). Their courses of care ranged from 1-3 visits per week, for 10-52 weeks based on presentation. (For the full numerical breakdowns beyond SDNN alone, read the full report at the reference provided below [1].)
All showed a sustained trajectory of improvement. It is this trajectory, and the sustained nature of the improvement, that makes the results significant. Many interventions including exercise and meditation can improve HRV temporarily; the observation of sustained rather than temporary increase in HRV is suggestive of the possibility of neuroplastic changes from the intervention delivered, which in this case was a series of adjustments intended to correct vertebral subluxation.
As this was a retrospective study, the data was clinical data and not research quality data, a critique Dr Amy states that she is well aware of, and offers that this study was about flagging a trend of sustained improvement.
“This is a grouping of six similar cases to say, ‘Hey there is a trend here.’ These patients are showing a trajectory of improvement over multiple time points, rather than before-and-after, which makes the approach something new and different than has been done elsewhere. I recognise that one of the criticisms that has been brought forth about this paper is that what has been presented is clinical data rather than research data. I totally get that. The data collected for this work was intended as a pre-feasibility study, meaning, can this system yield reproducible data so that future studies can be designed to quantitatively examine the observed phenom in a way that can generate valid statistics? This was a retrospective study, a “proof-of-concept” if you will, looking at trend, trajectory and change rather than absolute value. Clearly further higher level studies will be needed to confirm these findings and develop this line of investigation.”
Although Diversified and TTPT were the techniques used in this case, Dr Amy is quick to point out that the literature that currently exists around HRV shows improvements coming from a range of techniques and analysis systems, including CPB, NSA, and craniosacral.
“This is about chiropractic. This is not about technique. The specific technique or approach for analysis helps a person identify the subluxation they are going to correct. The sensory input that is generated by correction of the subluxation is not constrained to one technique or another. If we are all working with the subluxation, if we are all dealing with afferent input, integration and efferent input, it really doesn’t matter which [proverbial] cooking pan in your pantry you use. All techniques have their time and place for sure – it’s so great that we have different ways to approach different human (and animal) structures. But the purpose of the analysis technique and the adjusting technique is to identify and then correct what we have in common – and that is the subluxation.”
The term ‘vertebral subluxation’ was very much central to this paper. Dr Amy remarked:
“If we want these words and their meaning to become agreed upon, we have to use them – frequently, regularly, in a way that is supported. This was part of the strength that Dave [Russell] brought to this paper – being able to use the ASRFs conceptual definition of subluxation and support that with published evidence that chiropractic research has developed and continues to establish. To be able to say “this is what a vertebral subluxation is, the best we know right now. This is what we are correcting. These are the outcome measures we are using.” Using the term ‘Vertebral Subluxation’ in research journals in a way that is defined and supported is really important for chiropractic, in order to develop and claim the lexicon that differentiates us and the unique contribution chiropractic brings to healthcare. Publishing research with terms such as Vertebral Subluxation will help the profession to strengthen its position and our identity, and that’s becoming more possible now due to the work of folks who have been working hard to clearly define this term.”
What next?
HRV is something that can potentially offer insight into the impact of the adjustment on adaptability. “At this middle stage of life, we are starting to accumulate the effects of not sleeping, not taking proper nutrition, of working too hard, of not exercising enough – emotional, physical chemical stressors,” says Dr Amy of the cohort in the case series. “At this age we are starting to see these decreases in adaptability. If we are talking about a health trajectory as a generality, at any point in time a human is either getting sicker or healthier. There is no stasis. I can’t remember who said it, but one of my favourite quotes is that you cannot be in a state of decline and a state of growth at the same time. To take someone whose health trajectory is declining, and instead deliver an intervention which appears to not only reverse that naturally predicted decline in SDNN but improves and sustains it at a better level has a lot of promise.”
Chiropractors have often said that the intention of chiropractic care is to add years to life and life to years. A logical part of that concept is that adaptability is required. “By extension, this paper is providing supportive evidence for a contention that we as a field have put forth for many years. I think HRV is an area that can certainly be developed to provide further support for long-term vitality based care for correction of vertebral subluxation.” says Dr Amy. “I’m hoping that having put this possibility out into our profession that people will pick up on this and do the next step, to develop the controlled clinical trial, to work further on honing the variables and even getting research quality data.”
“This is how science works. Step by step. I’ve just tried to create one stepping stone, placed on steps others have created, in order to establish a foundation for further studies and future work.”
References & Terms
* This represents the Standard Deviation of Normal to Normal (SDNN) RR-intervals over a period of milliseconds. SDNN describes the overall HRV, and encapsulates both short and long term variability
[1] Haas A, Russell D (2018), “Sustained improvement of heart rate variability in patients undergoing a program of chiropractic care: a retrospective case series,” Chiropractic Journal of Australia, Volume 45, Number 4, pp. 339-358