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Anatomy & Physiology

Why Your Body Hurts: The Nervous System, Stress, Sensitivity, and the Modern Experience of Pain

May 18, 2026

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Pain is one of the most common reasons people begin searching for help for their bodies.

Sometimes it begins in one place: the jaw, neck, shoulders, lower back, pelvis, hips, knees, or hands. Sometimes it spreads. Sometimes it changes location. Sometimes the whole body feels stiff, tender, inflamed, tired, or strangely “on edge”.

And sometimes the most unsettling part is this: the pain feels very real, but the usual structural explanation does not seem to explain the whole picture.

This is exactly where a modern understanding of pain becomes so important.

For many years, people were taught to think about pain in a very narrow way: if something hurts, something must be damaged in direct proportion to the pain. But modern pain science has moved far beyond that model.

The International Association for the Study of Pain defines pain as an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage. Just as importantly, it distinguishes pain from nociception. Nociception is the neural process of detecting potentially harmful stimuli. Pain is the lived experience the nervous system produces.

That distinction changes everything.

It explains why pain can be intense without major tissue damage.
It explains why structural changes can exist without much pain.
And it explains why stress, fear, sleep, beliefs, sensitivity, and the state of the nervous system can profoundly shape what you feel.

This does not mean pain is imaginary.

It means pain is biologically real, but biologically more complex than most people were taught.

For a practical back-pain starting point, you may also want to read 10 Common Causes of Back Pain: What Really Triggers It and What Actually Helps.

Pain is an output of the nervous system, not a simple signal from tissue

One of the most important shifts in modern pain science is understanding that pain is not a passive message sent directly from tissues to the brain. It is an active protective experience generated by the nervous system.

If you cut your finger, sprain an ankle, overload a tendon, irritate a joint, or strain a muscle, specialised sensory receptors in the tissues can detect mechanical, thermal, or chemical threat. These receptors are called nociceptors.

They do not create pain by themselves.

They send information into the nervous system about possible danger. The nervous system then evaluates that information in context and may generate pain as a protective output.

The IASP terminology page defines nociception as the neural process of encoding noxious stimuli and nociceptive pain as pain arising from actual or threatened damage to non-neural tissue through activation of nociceptors.

This means pain is never only mechanical.

Even in an ordinary injury, there is more happening than “damage equals pain”. There is incoming sensory information, but there is also attention, memory, stress chemistry, previous experience, and the nervous system’s real-time estimate of danger.

Pain is the result of that whole evaluation.

That is why the same movement can hurt more in one context and less in another. That is why a body under stress often hurts more. That is why pain can persist after tissues have already improved.

A-delta fibres, C fibres, and why pain can feel sharp first and diffuse later

Pain is not only complex in cause. It is also complex in how it feels.

One useful distinction is the difference between A-delta fibres and C fibres.

A-delta fibres are thinly myelinated and conduct signals relatively quickly. They are associated with the first, sharper, more localised pain that often appears immediately after an acute insult.

C fibres are unmyelinated, conduct more slowly, and are more associated with the later, duller, heavier, more diffuse aching quality of pain.

This helps explain why pain can evolve over time.

A sensation that begins as sharp and precise may later become heavy, throbbing, sore, or difficult to localise. In persistent pain states, the body may move even further away from that early acute pattern and towards something broader, more sensitive, and harder to interpret.

Understanding this can be reassuring.

It reminds you that the changing quality of pain is not random. It reflects different mechanisms, different nerve pathways, and a nervous system that is responding dynamically rather than mechanically.

Three broad mechanistic pain descriptors: nociceptive, neuropathic, and nociplastic

One of the clearest ways to make sense of modern pain science is to understand that not all pain is created by the same mechanism.

Nociceptive pain

This is pain arising from actual or threatened damage to non-neural tissue through activation of nociceptors.

Think of an inflamed joint, an irritated tendon, an acute tissue strain, or a painful overload state. The IASP terminology page defines it in exactly those terms.

Neuropathic pain

This is pain caused by a lesion or disease of the somatosensory nervous system itself. In other words, the nerve pathway is affected.

Again, IASP defines neuropathic pain as pain caused by a lesion or disease of the somatosensory nervous system.

Nociplastic pain

This is one of the most important concepts for persistent and widespread pain.

IASP defines nociplastic pain as pain arising from altered nociception, despite no clear evidence of actual or threatened tissue damage that would explain the pain, and without evidence of a somatosensory lesion that would make it neuropathic.

This category matters because it gives language to the kind of pain many people experience when sensitivity, fatigue, stress, poor sleep, diffuse tenderness, and widespread symptoms become part of the picture.

It helps explain why a person may feel significant pain without a simple structural answer.

These categories are useful, but real life is often mixed. A person may have nociceptive input, some nervous-system sensitisation, and some neuropathic features at the same time.

Pain is not always neat.

That is one reason it needs thoughtful explanation rather than simplistic labels.

Peripheral sensitisation: why tissues become easier to trigger

In the earlier phases of pain, one important process is peripheral sensitisation.

When tissue is irritated or inflamed, local biochemical mediators such as prostaglandins, bradykinin, cytokines, and growth factors can lower the activation threshold of nociceptors.

In plain language, the local alarm system becomes easier to trigger.

Signals that might not have hurt much before can begin to feel significantly more painful. Mechanistic reviews describe how inflammatory mediators increase the responsiveness of peripheral sensory endings. See, for example, this PMC review on peripheral pain mechanisms and this review on pain hypersensitivity mechanisms.

This matters because it explains why the painful area can become locally “hotter” in a functional sense even without dramatic structural change.

The tissue environment itself can become chemically more excitable.

That is one reason why inflammatory load, repeated irritation, poor recovery, and excessive strain can all make pain easier to provoke.

But this is only part of the story.

Peripheral sensitisation explains increased sensitivity at the tissue level. It does not fully explain why pain spreads, why light touch may hurt, why symptoms can become disproportionate, or why sleep, stress, and fear can intensify the experience.

For that, we need to look at the central nervous system.

Central sensitisation: when the alarm system becomes over-responsive

If peripheral sensitisation makes tissues easier to trigger, central sensitisation makes the nervous system itself more responsive.

This is one of the most important mechanisms in persistent pain.

The central nervous system, particularly the spinal cord and brain, can become more efficient at amplifying nociceptive input. A useful formal definition comes from pain science literature: central sensitisation involves increased responsiveness of nociceptive neurons in the central nervous system to normal or even subthreshold input.

A classic review on this topic is Central sensitization: Implications for the diagnosis and treatment of pain.

At the neurophysiological level, this involves changes in synaptic efficiency and excitability. Reviews describe the role of glutamate, AMPA receptors, NMDA receptors, intracellular calcium signalling, and kinase-mediated processes that strengthen nociceptive transmission and help maintain hypersensitivity.

In simpler terms, repeated alarm signals can train the system to produce pain more easily.

This is where the phrase “the nervous system can learn pain” becomes meaningful.

Not because pain is imagined.
Not because the person is making it up.
But because neuroplasticity works in both directions.

The nervous system can learn overprotection. It can become very good at producing pain. And with the right conditions, it can also gradually learn safety again.

If this sensitivity pattern feels relevant to you, you may also want to read How Stress Changes the Body: Muscle Guarding, Nervous System Load, and Pain.

Hyperalgesia and allodynia: when pain changes quality

Once sensitisation develops, pain often changes not only in intensity, but also in quality.

Two useful terms here are:

Hyperalgesia — an increased response to a stimulus that is normally painful
Allodynia — pain caused by a stimulus that is not normally painful, such as light touch

These changes are part of why persistent pain can feel so confusing.

A person may notice that normal pressure feels excessive, clothing feels irritating, mild manual therapy feels too intense, or simple movement produces a surprisingly large reaction.

These experiences can be frightening if they are interpreted only as damage.

But in a sensitised nervous system, they make physiological sense.

The volume of the alarm system has been turned up.
The threshold has dropped.
The protective response has become easier to trigger.

The neuromatrix and the pain neurotag

One of the most useful models for understanding persistent pain is the idea that pain is generated by a distributed network rather than by one simple linear pathway.

This has often been described through ideas such as the neuromatrix, neurosignature, or pain neurotag.

The central insight is that pain emerges from the integration of many kinds of information:

movement
sensory input
emotions
beliefs
memories
smells
visual cues
previous painful experiences
social context
and threat appraisal

The nervous system weighs these inputs and may generate pain if the overall output tilts strongly enough towards danger.

This helps explain experiences that otherwise seem mysterious:

pain that appears before movement fully loads the tissue
pain that is stronger in stressful contexts
pain associated with certain environments or memories
pain that persists long after an acute injury has healed
pain that changes with fear, attention, reassurance, or education

The system is not being irrational.

It is protecting according to what it has learned.

Descending modulation: the brain can amplify pain or dampen it

Pain is not only driven from the body upward.

There are also descending modulatory pathways from the brain downward, and these pathways can either inhibit pain or facilitate it.

This is clinically very important because it means your state matters.

Sleep, confidence, fear, stress, attention, meaning, safety, social support, and language all influence pain modulation. They are not “soft extras”. They are part of the physiology.

If the nervous system is in a more threatened state, descending facilitation may increase. If the system feels safer, more predictable, and more regulated, pain inhibition tends to work better.

This is one reason explanation itself can be therapeutic. It is one reason supportive movement can help. It is one reason a calmer context can change how the body feels without any dramatic structural intervention.

Why stress can worsen body pain

Stress does not create every pain problem from nothing, but it can make an existing system much more reactive.

This is exactly why the biopsychosocial model of pain matters. Pain is not only biological, but it is not only psychological either. It is shaped by the interaction between biological factors, psychological factors, and social context.

Stress can intensify pain through several channels at once:

increased muscle guarding
autonomic arousal
poorer sleep
altered attention
greater threat monitoring
reduced pain inhibition
and increased inflammatory signalling

That is why people often notice that symptoms flare during emotionally overloaded periods, during prolonged work pressure, or after a phase of poor sleep and mental strain.

This is not “just stress”.

It is stress physiology influencing pain physiology.

This topic is explored more specifically in Stress at Work and Your Back: How the Nervous System Adds Tension.

Why sleep matters so much

Poor sleep is not just an inconvenience that happens alongside pain.

It often becomes part of the mechanism.

Sleep disturbance lowers pain tolerance, worsens fatigue, affects emotional regulation, and tends to make the nervous system more reactive the next day.

Pain disturbs sleep.
Poor sleep amplifies pain.
And the cycle can become self-reinforcing.

This is especially clear in widespread pain and fibromyalgia-type presentations. The NHS overview of fibromyalgia and its symptoms page describe common features such as widespread pain, stiffness, heightened sensitivity, fatigue, poor sleep, and cognitive difficulty. The NCCIH fibromyalgia overview also describes the broader symptom picture.

This does not mean every person with body pain has fibromyalgia.

It means that pain often becomes a whole-system issue, and sleep is one of the major regulators of that system.

For a fuller explanation, continue with Why Sleep Changes Pain: Sleep Quality, Recovery, and Body Sensitivity.

Why language changes pain

Words matter far more than most people realise.

Pain is shaped not only by tissues and nerves, but also by meaning. Threatening labels, dramatic explanations, and poorly contextualised scan findings can intensify fear, increase catastrophising, reduce a person’s sense of control, and make the body feel more fragile than it really is.

That is why language such as:

“degeneration”
“instability”
“your spine is crumbling”
“you are out of place”
“you must never bend”

can be so harmful when it is delivered without proper explanation.

It does not just affect mood.

It changes behaviour, expectation, and nervous-system threat processing.

A better pain conversation does not deny reality.

It explains reality without adding unnecessary fear.

This principle also matters deeply in posture and back-pain conversations. You may want to read How Words Change Pain: Language, Fear, Nocebo, and the Way We Experience the Body and The Myth of Perfect Posture: Why Sitting Up Straight Hurts.

Why scans and labels are not the whole story

One reason people become frightened is that imaging is often treated like a final answer.

But structural findings need context.

A scan can show changes that are meaningful, and it can also show changes that are common and incidental.

A report is not the same thing as your whole clinical picture.

A label is not the same thing as your full lived experience.

That is why a modern clinician does not ask only:

“What does the scan show?”

but also:

What do the symptoms do?
What is the sensitivity level of the system?
What is the sleep like?
What is happening with stress?
What is the person afraid of?
What can the body still tolerate?
What restores confidence?

Pain becomes much easier to understand when scans are interpreted inside the whole person rather than above them.

For a practical guide to staying calm around back-pain advice and imaging, you may also want to read Advice Chaos for Back Pain: How to Choose Safely.

Widespread pain, sensitivity, and the whole-person pattern

When the nervous system becomes more sensitive, the symptom picture often broadens.

A person may begin with one painful area and then also notice:

muscle stiffness and soreness
fatigue
headaches
jaw clenching
poor concentration
low mood
digestive or pelvic symptoms
poor sleep
neck and shoulder tension
skin sensitivity
feeling that the whole body hurts

This is one reason persistent pain can feel much bigger than one body part.

The system has become more globally reactive.

For the person living with it, this often feels deeply confusing. One day the back hurts most. Another day it is the neck, jaw, hips, or whole body.

But from a sensitivity perspective, that pattern is understandable.

A sensitised nervous system does not always stay neatly local.

Self-efficacy: one of the strongest protective factors

One of the most underrated concepts in pain recovery is self-efficacy.

Self-efficacy means your sense that you can still move, cope, participate, work, enjoy life, and gradually rebuild activity even while pain is part of the picture.

It is not denial.
It is not pretending pain is absent.
It is the growing sense that pain does not fully control your life.

This matters enormously.

When a person feels:

“My body is fragile.”
“I should avoid everything.”
“Pain means I am damaging myself.”
“I cannot trust movement anymore.”

the nervous system tends to become more guarded.

When a person gradually regains:

understanding
tolerable movement
confidence
agency
and a sense of safety

the whole system often becomes easier to calm.

Pain recovery is not only about reducing symptoms.

It is also about rebuilding trust.

For a deeper explanation of this topic, continue with Self-Efficacy and Pain: Why Confidence Changes the Way You Experience the Body.

DIMs and SIMs: danger input signals and safety input signals

A very practical way to think about persistent pain is through the idea of danger input signals and safety input signals.

Some things in life push the system towards threat:

frightening explanations
catastrophic beliefs
overload
uncertainty
sleep deprivation
social isolation
repeated failure experiences
doom-scrolling about symptoms

Other things push the system towards safety:

a clear explanation
a plan you understand
movement you can tolerate
a supportive practitioner
enjoyable activity
a calmer sleep rhythm
feeling listened to
feeling stronger and more capable

This is one of the most useful shifts in persistent pain.

Instead of asking only:

“Where does it hurt?”

you begin asking:

What is amplifying danger?
What increases trust?
What makes the body brace more?
What helps the system feel safer?

Where movement fits in

Movement matters, but the old conversation around movement is often too crude.

The goal is not complete rest until symptoms vanish. The goal is not pushing through everything. And the goal is not forcing the body because “exercise is always good”.

The modern answer is usually:

graded, tolerable, regular movement.

The body needs loading, but it also needs recovery.

Tissues generally become healthier through intelligent loading, not through underuse. At the same time, excessive repetitive load, poor recovery, or movement performed inside high fear can make things worse.

This is where guidance matters.

The most helpful movement is usually movement that:

reduces fear
restores variability
builds trust
matches the current capacity of the system
and leaves the person feeling more capable rather than more defeated

For a gentle entry point, you may want to read Gentle Back Pain Relief Exercises at Home: 6 Simple Movements to Reduce Tension and Restore Ease.

If your symptoms are mainly back-related, continue with Yoga Therapy for Back Pain, Posture, and Everyday Movement.

Where yoga therapy fits into this picture

Yoga therapy is not a replacement for medical assessment when diagnosis, medication, or specialist care is needed.

But for pain shaped by nervous-system sensitivity, chronic bracing, loss of body trust, stress physiology, poor recovery, and fear of movement, yoga therapy can be highly relevant.

Why?

Because it can work at several levels at once:

movement variability
breath regulation
autonomic downshifting
interoceptive awareness
reduced guarding
pacing
graded exposure
rest without collapse
and a calmer relationship with sensation

This aligns well with broader scientific and public-health directions too. The NCCIH overview of chronic pain and complementary health approaches and its science digest on complementary approaches for chronic pain note that approaches such as yoga, mindfulness, tai chi, qigong, and related practices may help some chronic pain conditions.

The real value here is not one pose.

It is helping the whole system move from hypervigilance towards steadiness.

If you want to understand how yoga therapy is adapted to the individual, you may also want to read Why Two People With the Same Diagnosis Need Different Yoga Therapy Plans.

This understanding should make you calmer, not careless

A modern pain model should reduce unnecessary fear, but it should not erase medical caution.

Pain still needs proper assessment when it is:

new and severe
linked with trauma
accompanied by fever
associated with unexplained weight loss
progressing with weakness or neurological loss
affecting bladder or bowel function
or behaving in a way that suggests something more serious

A whole-person pain model is not the same as saying:

“Everything is just sensitivity.”

It means understanding when the system is overprotective and when something needs medical evaluation first.

If you want to understand these boundaries more clearly, you may also want to read Yoga Therapy Alongside Medical Care: When Support Needs Boundaries.

Final thought

Pain is not only about tissue.
It is not only about structure.
It is not only about stress.
It is not only about thoughts.
And it is not only about mindset.

Pain is a real protective experience generated by a nervous system that is constantly integrating tissue state, inflammatory chemistry, nerve signalling, previous experience, stress load, sleep, beliefs, language, context, and perceived safety.

That is why two people can have similar scans and very different pain.

That is why a small load can hurt a lot in one phase and much less in another.

That is why language can worsen pain.

That is why understanding can reduce fear.

And that is why recovery is rarely about one magic technique, but about helping the whole system feel safer, stronger, and more capable again.

Sources

FAQ

Why does my body hurt when there is no clear injury?
Pain can be influenced by more than tissue damage. Stress, poor sleep, nervous-system sensitivity, fear, previous experiences, inflammation, muscle guarding, and reduced recovery can all affect how strongly the body produces pain.

Does this mean pain is imaginary?
No. Pain is real. The point is that pain is produced by the nervous system, and the nervous system uses many kinds of information when deciding whether to protect the body with pain.

What is central sensitisation?
Central sensitisation means the central nervous system has become more responsive to input. The pain alarm system becomes easier to trigger, so normal or mild sensations may feel more painful than expected.

What is nociplastic pain?
Nociplastic pain is pain that arises from altered nociception without clear evidence of tissue damage or nerve lesion that fully explains the pain. It is often relevant in persistent, widespread, or sensitivity-related pain patterns.

Can stress really make pain worse?
Yes. Stress can increase muscle guarding, disturb sleep, increase vigilance, reduce pain inhibition, change breathing, and make the nervous system more reactive. This does not mean pain is “just stress”; it means stress affects pain physiology.

How can yoga therapy help with nervous-system-related pain?
Yoga therapy may support pain care by helping with breath regulation, movement confidence, pacing, relaxation, body awareness, reduced guarding, and a calmer relationship with sensation. It is complementary support, not a replacement for medical assessment when needed.

Disclaimer

This article is for educational purposes only and does not replace medical advice, diagnosis, physiotherapy, psychological care, medication, or treatment. Pain can have many causes, and some symptoms require medical assessment. If you have new or severe pain, pain after trauma, fever, unexplained weight loss, progressive weakness, numbness, bladder or bowel changes, severe mental-health distress, or symptoms that feel unusual or worrying, please seek appropriate professional support.