Vagal Tone, Chiropractic, and the Nervous System
Vagal tone is one way we describe how well the body can shift out of stress and back into regulation. It reflects the adaptability of the autonomic nervous system: the body’s ability to breathe, digest, rest, repair, connect, recover, and respond appropriately to life.
From a chiropractic perspective, this matters because the spine is not just a stack of bones. It is a moving, sensory-rich structure that constantly sends information to the brain. When spinal segments lose healthy motion or become subluxated, the brain may receive altered input from the body. Dr. Heidi Haavik’s research has shown that adjusting dysfunctional spinal segments can change how the brain processes sensory information, particularly in areas involved with sensorimotor integration and the prefrontal cortex.
The Branches of the Nervous System
The nervous system can be understood in three broad ways.
The central nervous system includes the brain and spinal cord. This is the command centre.
The peripheral nervous system includes the nerves that travel from the spine to the rest of the body.
The autonomic nervous system helps regulate automatic functions such as heart rate, breathing, digestion, immune response, temperature, blood flow, and stress recovery. It includes the sympathetic and parasympathetic branches.
The sympathetic branch is often called the fight-or-flight system. It helps us mobilize, protect, react, run, defend, and survive.
The parasympathetic branch is often called the rest-digest-heal system. The vagus nerve is a major part of this branch. It supports digestion, heart rhythm, breath regulation, inflammation control, emotional regulation, social engagement, and recovery.
The motor system sends messages from the brain to the muscles.
The sensory system sends messages from the body back to the brain. This is especially important in chiropractic because joints, muscles, ligaments, fascia, and spinal tissues are loaded with sensory receptors.
Why Segmental Motion Matters
Healthy spinal motion creates healthy neurological input. Every time a spinal joint moves well, it feeds the brain with accurate information about position, movement, balance, pressure, and safety.
When segmental motion is restricted, irritated, or poorly coordinated, the brain may receive distorted information. This can influence posture, muscle tone, balance, breathing patterns, stress responses, and how safe or guarded the body feels.
This is why chiropractic is not simply about pain. It is about improving the quality of communication between the body and brain.
Haavik’s work supports the idea that chiropractic adjustments influence brain function through changes in sensory processing and sensorimotor integration. Research has shown changes in cortical processing after spinal manipulation of dysfunctional segments.
Chiropractic and Vagal Tone
Chiropractic does not “treat” the vagus nerve like a condition. Rather, chiropractic assesses and adjusts areas of subluxation to support clearer communication through the spine and nervous system.
Vagal tone is commonly measured through heart rate variability, or HRV. HRV reflects how adaptable the autonomic nervous system is. The research on spinal manipulation and HRV is still developing and mixed: some studies suggest autonomic changes may occur, while a 2024 review found low-quality evidence that spinal manipulation did not clearly influence autonomic measures such as HRV.
So the honest clinical conversation is this: chiropractic care may support nervous system regulation by improving spinal input and brain-body communication, but we should avoid claiming it directly “fixes” vagal tone.
What Causes Subluxation?
Subluxation can be created by stressors the body cannot fully adapt to. These stressors may be physical, chemical, hormonal, mental, or emotional.
For adults, this may include poor posture, car accidents, falls, sports injuries, repetitive desk work, pregnancy, birth trauma, lack of movement, poor sleep, inflammation, illness, surgery, emotional stress, grief, worry, or chronic overwhelm.
For pregnancy and postpartum, the body is adapting constantly. Hormonal changes soften ligaments. The pelvis changes. The spine compensates. Sleep changes. Birth may involve induction, medications, long labour, surgical birth, pushing stress, breastfeeding positions, emotional worry, and the constant nervous system demand of caring for a baby.
For babies and children, stressors may include intrauterine positioning, birth pressure, assisted delivery, C-section, feeding challenges, falls, growth spurts, poor sleep, emotional stress, screens, reduced movement, and developmental strain.
The body creates subluxation as a protective strategy. It is often the body’s attempt to guard, stabilize, or survive. Chiropractic helps assess and adjust those areas so the body can move toward better function, adaptability, and regulation.
The Big Picture
The goal is not simply to feel better. The goal is to function better.
A resilient nervous system can move between effort and recovery. It can respond to stress without getting stuck there. It can digest, sleep, heal, connect, grow, and adapt.
Chiropractic care supports this by improving spinal motion, reducing neurological interference, and helping the brain receive clearer information from the body. When the spine moves better, the brain can map the body more accurately. When the brain maps the body more accurately, the body often has a greater opportunity to regulate, coordinate, and heal.