For all that chiropractic care proposes about the relationship between spinal function and nervous system performance, the profession has long faced a practical problem: how do you actually measure it rigorously? A 2024 feasibility study from Dr Tyson Perez (DC, PhD), Emily Drake and Stephanie Sullivan (DC, PhD) takes a serious crack at answering that question, and the findings are certainly worth paying attention to. Best of all, it has applications for the advancement of chiropractic research.
This study began with lofty goals in mind – that of filling a gap in the technology to accurately measure what is going on in the central and peripheral nervous systems and how they might respond to chiropractic adjustments. Researchers have recognised for some time that high-quality studies examining how the brain responds to chiropractic adjustments are needed, but also that the tools to properly test our profession’s core claim regarding subluxation, nervous system optimisation and functional health impacts have been difficult to come by. This study represents an early but meaningful attempt to change that.
The feasibility study by Perez, Drake, and Sullivan asked a foundational question: can we develop a practical, tolerable, and high-quality battery of neurophysiological tests that measures both central nervous system (CNS) and peripheral nervous system (PNS) function? Can it be done in a way that is useful across both resting and non-resting conditions and within a single session?
It was a big goal to take on. Nevertheless, Perez et al created a new battery of tests aimed at answering the need for “more robust designs that employ methodologically sound neurophysiological data collection and processing procedures. [1]” Once their battery and procedures were designed and put to the test. Testing involve working with eleven healthy study participants from the Atlanta area , who were put through a comprehensive assessment battery that included:
- Resting-state EEG — 64-channel measurement of brain electrical activity at rest
- Event-Related Potentials (ERPs) — brain responses to an auditory stimulus task, probing cognitive processing
- Electrocardiography (ECG) and Impedance Cardiography (ICG) — measuring heart rate variability and the pre-ejection period (PEP) as respective markers of parasympathetic and sympathetic nervous system activity
- Electrodermal Activity (EDA) — skin conductance as a further sympathetic nervous system indicator
- Deep breathing — a paced breathing protocol to quantify respiratory sinus arrhythmia
- Isometric Handgrip Challenge — a sustained gripping task designed to provoke a cardiovascular stress response, with continuous blood pressure monitoring
- Patient Reported Outcomes (PROs) — validated questionnaires covering autonomic symptoms, cognitive flexibility, and mental fatigue
The battery was assessed against five feasibility criteria: efficiency, compliance, tolerability, acceptability, and data quality, using a traffic light (red/amber/green) progression framework.
The headline finding is straightforward: the battery is feasible, with some modifications needed. Of the eleven adults, ten finished the study, with one withdrawing due to an adverse event (discolouration of the middle finger when a finger cuff was applied, likely due to an undisclosed prior medical condition). All others completed the program and tolerated it well. However, the adverse finding was taken into consideration and the modification needs were noted as part of the study’s results.
Researchers found the following:
Efficiency held up well. Sessions averaged approximately 83 minutes, within the team’s 90-minute target.
Compliance with pre-session lifestyle restrictions (avoiding caffeine, alcohol, strenuous exercise, and similar) was largely solid. The main exception was water intake: approximately 36% of participants drank more than the protocol allowed in the four hours before testing. The researchers have since relaxed this restriction, recognising that hydration needs vary significantly between individuals.
Tolerability was high. Ten of eleven participants completed the full battery. The one withdrawal occurred after a participant experienced circulation problems following application of the blood pressure finger cuff. It was subsequently disclosed that they had Raynaud’s phenomenon, a condition involving vasospasms in the digits under stress. The team has flagged this as something future studies using finger cuff monitoring need to screen for.
Data quality was strong for most measures. EEG, ECG, ICG, and ERP data largely met quality thresholds. Two assessments, however, produced unusable data:
- All EDA recordings were discarded because skin conductance levels fell far below the expected range. Follow-up testing indicated the pre-applied electrode gel had been applied in insufficient quantities. The preparation procedure has since been revised.
- All continuous blood pressure files from the handgrip challenge had to be discarded due to a software export limitation that prevented the offline analysis the team needed. This measure has since been replaced with ECG and ICG monitoring during the handgrip, capturing both sympathetic and parasympathetic reactivity simultaneously, and reducing the amount of hardware participants need to wear.
Acceptability was high across the board. Of 14 survey items, 13 met the top-tier criterion. The one exception related to pre-session lifestyle restrictions as addressed by the protocol changes noted above.
Why this study matters:
This study is less about results and more about infrastructure. By combining EEG-based Central Nervous System (CNS) assessment with multiple validated Peripheral Nervous System (PNS) measures across both resting and reactive conditions, this battery is designed to test, with genuine scientific rigour, whether adjustments produce measurable changes in nervous system function.
The authors are clear that this is a first step. Chiropractic intervention trials using a modified version of this battery were already underway in clinical populations at the time of publication.
They are also appropriately candid about limitations. The sample was small by design, drawn from a university community, and demographic data was lost entirely due to a technical failure in their data collection platform; a significant gap they addressed through improved backup protocols. The resting-state EEG and Autonomic Nervous System recordings were also captured on separate amplifiers without precise synchronisation, limiting the ability to analyse real-time CNS-PNS interactions. The lab has since moved to a single amplifier for both signals.
The battery has since been expanded to include measures of somatomotor function, with future trials planned to incorporate longitudinal designs, control and treatment groups, and blinded outcome assessors.
For those invested in building a credible evidence base for chiropractic and nervous system research, studies like this one represent exactly the kind of foundation the profession need: careful, transparent, and willing to report what didn’t work. In this case, it was a relatively easy fix that could be solved with some software tweaks, adjustments to skin conducting thresholds and better pre-screening.
This all means that we are likely to have a new set of options for research-grade data available to chiropractic researchers in the near future. And this of course, is in the service of better quality chiropractic research service our profession and the people we care for.
This blog is based on: Perez TM, Drake E, Sullivan S. Assessing central nervous system and peripheral nervous system functioning in resting and non-resting conditions in a healthy adult population: a feasibility study. Chiropractic Journal of Australia, 2024.
