Red X iconGreen tick iconYellow tick icon

This programme of work explores the neuroendocrine mechanisms of manual therapy through a series projects working with people with concussion symptoms.

About our current work: Human response to neck treatment following concussion

Gerard Farrell imageThis research explores the neuroendocrine mechanisms of manual therapy, specifically, whether manual therapy can modulate the human stress response.

This research is part of Gerard Farrells PhD studies.

About this research

Moving the joints in your neck is a common, and effective, treatment for concussion symptoms, but also many other musculoskeletal conditions of the neck. However, the reason for its positive effect is not fully understood. Therefore, the goal of this body of research has been to determine whether a different response happens after moving the joints at the top or bottom of the neck in healthy people (to work out the normal response) and in people with persistent concussion symptoms.

The response we were interested in is the human stress response. This is the response you have when you are exposed to stress i.e. if you have to give a speech in front of thousands of people, your heart may race, you may get sweaty, and you may get hypervigilant. This is a heightened stress response. In the same situation, some people may be the opposite, and have a dampened stress response. This response is always somewhat active (baseline) and ready to go when required (reactivity). But in some instances or populations it doesn't work as well. This can lead to a less efficient response to stress, which can potentially lead to prolonged illness or symptoms. So can moving the joints in different locations of the neck be used to selectively modulate the stress response? Lets find out.

Learn about what we've discovered so far

Our first studies results: Working with people who have no pain, illness, or injuries

This study set out to see whether there is a different response depending on whether one mobilised (gentle oscillations of the neck joints-common physiotherapy treatment) the top or bottom of healthy people's neck. The response we were looking at is the human stress response. 

What our study found is that the main stress hormone, cortisol, DECREASES 30-minutes after mobilising the BOTTOM of people's neck. What we also found was a trend for cortisol to INCREASE the night after mobilising the BOTTOM of people's neck. This last finding, a trend for cortisol to increase the night after mobilising the bottom of people's necks, is interesting. Especially when you consider that people with persistent post-concussion symptoms and long-COVID often have low levels of cortisol. Maybe mobilising the lower part of the neck is a novel treatment to increase cortisol levels? Continue reading to find out what happens when we perform the same neck mobilisations in people with persistent post-concussion symptoms.

Our second studies results: Working with people who have persistent concussion symptoms

The first study showed that we may be able to stimulate the human stress response in a different direction depending on whether you mobilise the top or bottom of someone's neck. That was on healthy individuals though. What we know is that people with persistent concussion symptoms may have a dysregulated stress response (the literature review of my thesis showed this), meaning they may response differently to the mobilisations.  This study directly followed up from our first study, setting out to see whether there is a different response depending on whether one mobilised the top or bottom of people's neck who have persistent post-concussion symptoms (such as headache, dizziness, fatigue, etc).

What our study found is that the main stress hormone, cortisol, DECREASES 30-minutes after mobilising the BOTTOM of people's neck. But what was also interesting, is that there was a trend for cortisol to INCREASE the night after mobilising the BOTTOM of people's neck and for cortisol to DECREASE the night after mobilising the TOP of people's neck. This trend supports the idea that lower neck mobilisation can be used to increase the stress response in populations who may have a decreased response, and upper neck mobilisation can be used to decrease the stress response in populations who may have an increased response.

What this study also found is that the autonomic nervous system, specifically the 'rest and digest' component (parasympathetic or vagal), INCREASED 30-minutes after mobilising the TOP of people's neck. This finding supports the idea that upper neck mobilisation can be used to decrease the stress response in populations who may have an increased response. This finding is interesting when you consider that many populations often have a decreased 'rest and digest' component of the autonomic nervous system, such as Postural Orthostatic Tachycardia Syndrome (POTS), Ehler Danlos Syndrome (EDS). Maybe mobilising the upper part of the neck is a novel treatment to increase the 'rest and digest' component of the autonomic nervous system?

Where to next?

I've recently completed my PhD and am currently working in the School of Physiotherapy Clinics, incorporating my research into clinical practice. I have a special interest in managing conditions that can be characterised by dysautonomia (also known as autonomic dysfunction or stress response dysfunction). Such conditions include Postural Orthostatic Tachycardia Syndrome (POTS), Ehler Danlos Syndrome (EDS), Hypermobility Spectrum Disorders (HSD), persistent post-concussion symptoms. Understanding the person, their condition and its underlying physiology, and their symptoms allows the appropriate intervention to be tailored to that person.

Regarding research, I'm in the process of publishing the results of my thesis in scientific journals, and will be applying for funding to continue this line of research.

Acknowledgements

I would just like to take this opportunity to thank anyone why has been involved in any way with my thesis. But of particular emphasis, I would like to thank all my participants. Each of you gave up your time and are one of the key reasons this study was able to occur. In reality, without you volunteering your time, there would be no study.

Publications

Farrell G, Bell M, Chapple C, Kennedy E, Sampath K, Gisselman AS, Cook C, Katare R, Tumilty S. Autonomic nervous system and endocrine system response to upper and lower cervical spine mobilization in healthy male adults: a randomized crossover trial. J Man Manip Ther. 2023 Feb 16:1-14. doi: 10.1080/10669817.2023.2177071. Epub ahead of print. PMID: 36794952.https://pubmed.ncbi.nlm.nih.gov/36794952/

Gerard Farrell, Sizhong Wang, Cathy Chapple, Ewan Kennedy, Angela Spontelli Gisselman, Kesava Sampath, Chad Cook and Steve Tumilty. (2022). Dysfunction of the stress response in individuals with persistent post-concussion symptoms: a scoping review, Physical Therapy Reviews, 27:5, 384-405, DOI:10.1080/10833196.2022.2096195

Gerard Farrell, Sizhong Wang, Cathy Chapple, Ewan Kennedy, Angela Spontelli Gisselman, Kesava Sampath, Chad Cook & Steve Tumilty. (2022). Dysfunction of the stress response in individuals with persistent post-concussion symptoms: a scoping review.  Physical Therapy Reviews 27:5, pages 384-405, DOI: doi.org/10.1080/10833196.2021.1948752

The team

Study lead: Gerard Farrell (PhD candidate and Professional Practice Fellow at the School of Physiotherapy Clinics)
Email gerard.farrell@otago.ac.nz

  • Associate Professor Steve Tumilty (primary supervisor)
  • Dr Cathy Chapple (secondary supervisor)
  • Dr Ewan Kennedy (secondary supervisor)
  • Dr Kesava Sampath (external advisor)
  • Dr Angela Gisselman (international advisor)
  • Dr Chad Cook (international advisor)

This study is supported by a Stanley Paris PhD Fellowship and University of Otago Doctoral Scholarship.

Back to top