Recovery in POTS, Long COVID and Related Disorders:
- Graham Exelby
- Aug 10
- 8 min read
Updated: 4 hours ago
A Progressive Clinical and Scientific Exploration of Recovery
Dr Graham Exelby
This work did not begin with a new theory. It began with patients.
Over approximately 15 years, and through the assessment of more than 700 patients with POTS, Long COVID and related disorders, I repeatedly encountered patients whose illness could not be satisfactorily explained by existing diagnostic models. Many were profoundly disabled despite apparently reassuring routine investigations. Others carried multiple diagnoses—POTS, ME/CFS, fibromyalgia, migraine, gastrointestinal disorders, hypermobility, thoracic outlet abnormalities, mast-cell-associated symptoms and chronic pain—yet the boundaries between these conditions often appeared remarkably indistinct.
More importantly, patients sometimes improved when physiological abnormalities apparently unrelated to their diagnostic label were identified and addressed.
Over time, recurring patterns emerged. What initially appeared to be separate problems involving the autonomic nervous system, circulation, brain, gastrointestinal tract, musculoskeletal system, metabolism and immune system increasingly appeared interconnected.
Those observations progressively changed the questions being asked.
Instead of asking only: “What disease does this patient have?”
another question became increasingly important: “What is preventing this patient from adapting normally?”
That question became the foundation of the Recovery Concept and ultimately the Adaptive Physiology Framework developed throughout this work.
Adaptive Physiology: Why Similar Abnormalities Produce Different Symptoms
One of the most important lessons from this research has been that anatomical abnormality does not necessarily equal physiological disease.
Mechanical and vascular abnormalities—including thoracic outlet compression, jugular venous obstruction, altered cranio-cervical mechanics, Nutcracker anatomy, May–Thurner anatomy, pelvic venous congestion, altered coeliac or superior mesenteric artery relationships, spinal rotation and altered thoraco-diaphragmatic mechanics—may sometimes be demonstrated in people who remain remarkably well.
Other individuals with apparently similar abnormalities develop severe orthostatic intolerance, head pressure, pain, cognitive dysfunction, post-exertional malaise, gastrointestinal disturbance, migraine or profound fatigue.
The anatomy alone therefore cannot explain the phenotype.
The difference may lie in adaptive capacity.
Human physiology possesses substantial redundancy and reserve. Collateral venous pathways develop. Autonomic responses alter vascular tone, heart rate and cardiac output. Cerebral autoregulation protects oxygen delivery. Respiratory and musculoskeletal systems compensate for structural variation. Metabolic pathways alter substrate utilisation according to demand. Neuroendocrine, immune and repair systems continually respond to physiological stress.
For years, and sometimes decades, these adaptations may allow significant anatomical or physiological imperfections to remain clinically silent.
Symptoms may emerge when the cumulative physiological demand exceeds the capacity of those compensatory systems.
This is the central concept of Adaptive Physiology.
Adaptive reserve is not a single measurable variable. It is an emergent property of multiple interacting systems—including vascular, autonomic, neurological, metabolic, immune, lymphatic, extracellular-matrix, respiratory and musculoskeletal physiology.
Two people may therefore have remarkably similar anatomy but completely different symptoms because their ability to compensate is different.
This may also help explain why illness sometimes appears after an additional physiological stressor. Infection, COVID-19, trauma, surgery, rapid growth, pregnancy, hormonal change, prolonged stress or changes in physical loading may not necessarily create every underlying abnormality. They may instead expose a physiological system that had previously been compensating successfully.
The clinical problem then becomes one of determining which factors are driving the loss of adaptation, which are amplifying it, and which can realistically be changed.
From Adaptive Physiology to Recovery Failure
Patients with POTS, Long COVID, ME/CFS and related disorders frequently present with an extensive constellation of symptoms: orthostatic intolerance, post-exertional malaise, brain fog, chronic fatigue, pain, autonomic instability, migraine, sleep disturbance and gastrointestinal dysfunction.
These manifestations are traditionally divided between specialties and frequently treated individually.
The framework developed throughout this work asks whether, in at least a proportion of patients, they may instead represent downstream manifestations of disruption within an interconnected physiological network.
The concept of Recovery Failure describes a dynamic state in which the biological systems responsible for maintaining homeostasis and recovering from physiological stress progressively lose their capacity to do so.
This does not imply that POTS, Long COVID, ME/CFS or related disorders have a single cause. They clearly do not.
Nor does it imply that every mechanism described throughout these chapters occurs in every patient.
The proposition is different:
Different initiating events and different combinations of physiological abnormalities may converge upon a similar state of impaired adaptation and reduced physiological reserve.
The resulting clinical phenotype will depend upon which systems are affected, the magnitude of the physiological disturbance and the adaptive capacity of the individual.
The Physiological Bottleneck Framework
The Physiological Bottleneck Framework developed from this reasoning.
A physiological bottleneck is a component of the integrated system that has become sufficiently constrained that it begins to limit adaptation or recovery elsewhere.
Depending upon the individual, a bottleneck may involve preload, regional blood flow, cerebral perfusion, venous drainage, autonomic regulation, tissue oxygen delivery, lymphatic drainage, extracellular-matrix function, neuroimmune signalling, metabolism, respiratory mechanics or musculoskeletal function.
Frequently, several coexist. Importantly, the dominant bottleneck may change during recovery.
Correcting one significant physiological constraint may expose another that was previously concealed by the severity of the first. Recovery can therefore become a process of sequential physiological restoration rather than a response to a single intervention.
This changes the clinical question from: “Which treatment is appropriate for this diagnosis?” to: “Which physiological bottleneck is currently preventing further recovery, and who is best equipped to address it?”
As successive constraints are reduced, physiological reserve may expand. Autonomic regulation may become more stable, tolerance of physical and cognitive stress may improve, and the threshold at which symptoms are generated may progressively increase.
The objective is therefore not simply symptom suppression.
It is restoration of the physiological conditions that allow the body to adapt again.
A Multidisciplinary Approach to Recovery
Adaptive physiology is an emergent property of multiple interacting biological systems. Its restoration therefore cannot reasonably belong to a single medical specialty or therapeutic discipline.
Mechanical, vascular, autonomic, metabolic, lymphatic, rehabilitative and selected pharmacological interventions should not necessarily be regarded as competing explanations or competing treatments. They may be addressing different components of the same physiological network.
The practical philosophy underlying this framework can be summarised in three principles:
Understand what is happening.
Restore what can be restored.
Seek help for what cannot be restored within your own discipline.
The role of the clinician or therapist is therefore not to explain every component of the patient's illness personally. It is to recognise the limits of their own discipline while understanding how their contribution fits within the larger physiology of recovery.
This is particularly important in complex disorders where structural, haemodynamic, neurological, metabolic and immune abnormalities may interact.
Clinical Observation: Adaptive Reserve and Environmental Stress
Even relatively modest physiological stresses may become clinically important when adaptive reserve is limited.
Many patients, for example, report worsening symptoms with approaching storms, changing humidity or rapid changes in barometric pressure. Such observations are easily dismissed because they do not fit comfortably within conventional disease models.
Within an Adaptive Physiology Framework, however, environmental change does not need to be the primary cause of disease.
It may simply represent another physiological demand.
An individual with substantial adaptive reserve accommodates that demand without noticeable symptoms. A patient whose compensatory systems are already operating close to their limits may cross a physiological threshold and experience worsening pain, fatigue, head pressure, autonomic instability or cognitive dysfunction.
This seemingly simple observation illustrates an important principle running throughout this work:
The magnitude of an external stressor does not necessarily determine the magnitude of the clinical response. The available adaptive reserve may be equally important.
The Evolution of the Recovery Concept
The framework presented here developed progressively through clinical observation, physiological investigation, multidisciplinary collaboration and repeated reassessment of patients over many years. It required movement across conventional specialty boundaries.
Orthostatic intolerance led to questions about preload.
Preload led to venous obstruction, venous capacitance and collateral circulation.
Head pressure led towards cerebral venous drainage, cerebrospinal fluid dynamics and lymphatic outflow.
Coathanger pain and migraine led back towards the cranio-cervical region, thoracic outlet and sympathetic nervous system.
Gastrointestinal symptoms led towards the coeliac plexus, abdominal vascular relationships and thoraco-diaphragmatic mechanics.
Post-exertional malaise led towards tissue oxygen delivery, neurovascular regulation, mitochondrial metabolism and metabolic reserve.
Persistent illness following infection led towards endothelial and pericyte biology, immune signalling, extracellular-matrix remodelling and the biology of tissue repair.
Gradually, apparently separate observations began to converge. This work is an attempt to explore that convergence.
Established Science, Clinical Observation and Working Hypothesis
An important distinction applies throughout these chapters.
The framework brings together several different levels of evidence.
Some components describe well-established anatomy and physiology.
Others draw upon published experimental and clinical research from fields that are not commonly considered together.
Some derive from recurring observations within our multidisciplinary clinical cohort.
Others are working physiological hypotheses generated by integrating those observations with established biological mechanisms.
These categories should not be confused.
The purpose of this work is not to present hypothesis as established fact. It is to identify reproducible clinical patterns, examine whether existing science can explain them, and where it cannot, develop biologically plausible hypotheses capable of being tested.
Some of the proposals within these chapters will undoubtedly require modification as better evidence becomes available.
That is how the framework should evolve.
Progressive Release of the Chapters
Recovery in POTS, Long COVID and Related Disorders is being released progressively as individual chapters complete their final clinical, scientific and reference review.
This reflects the nature of the work itself.
The framework spans autonomic regulation, haemodynamics, cerebral and systemic venous drainage, tissue oxygenation, cerebrospinal fluid dynamics, lymphatic and glymphatic function, extracellular-matrix biology, metabolism, immune signalling and musculoskeletal mechanics. Many of the later chapters build directly upon physiological principles established in earlier sections.
Rather than delay access until every component of the manuscript is complete, chapters that have reached a sufficiently mature stage will be released individually as PDF documents on this website.
Each chapter should therefore be regarded as part of a larger evolving physiological framework, not as an isolated explanation of POTS, Long COVID, ME/CFS or any related disorder.
No single mechanism described within these chapters is proposed to explain every patient. Indeed, the central premise of the Recovery Concept is precisely the opposite: similar clinical syndromes may emerge from different combinations of physiological constraints acting upon individuals with different levels of adaptive reserve.
As further chapters are completed, they will be progressively added to this page.
Earlier chapters may also undergo revision where subsequent work provides important clarification, stronger supporting evidence or improved integration between components of the framework.
The intention is that this website will progressively become the complete work while allowing patients, clinicians, therapists and researchers access to individual chapters as soon as they are ready for release.
About the Chapters
Each downloadable PDF forms part of the progressively released manuscript Recovery in POTS, Long COVID and Related Disorders and should be read within the broader Adaptive Physiology and Recovery Failure framework developed throughout the series.
Where proposed mechanisms extend beyond established evidence, they are presented as working physiological hypotheses intended to stimulate further clinical and scientific investigation.
The chapters are not intended to provide individual medical advice or a prescriptive treatment protocol. Their purpose is to provide a physiological framework through which complex and apparently disconnected symptoms may be reconsidered, investigated and, where possible, addressed.
Chapters
Available for Reading
Completed chapters will be added below as individual PDF documents.
Several additional chapters are currently undergoing final editorial, scientific and reference review and will be released progressively as they are completed.
Further chapters addressing POTS, Long COVID, post-exertional malaise, metabolic reserve, cranio-cervical physiology, thoraco-diaphragmatic integration, abdominal vascular and autonomic physiology, and multidisciplinary restoration of adaptive capacity will follow as the manuscript develops.
The Objective
This manuscript is not designed to be read as a treatment protocol, although treatment where appropriate is included. This is particularly relevant in Long COVID as the background knowledge of COVID pathology has become available.
It is an attempt to provide patients with a way of understanding why apparently unrelated symptoms may be connected; clinicians with a framework for looking beyond individual diagnostic labels; therapists with a physiological context for the contribution of their disciplines; and researchers with hypotheses that can be challenged and tested.
Ultimately, the Recovery Concept asks a deceptively simple question:
What does the human body require in order to recover?
If disease emerges when physiological demands exceed adaptive capacity, then recovery may require more than treating the disease label.
It may require identifying what is preventing adaptation, restoring what can be restored, and progressively rebuilding the physiological reserve that allows normal life to resume.
Protocols treat diseases. Physiology restores patients.
A Companion Paper- "Head Pressure, Migraine and Dysautonomia:
An Integrated Hydraulic–Neurovascular Framework Linking the Brain, Neck and Body" is a hard read but important to understand how these becomes manifest in brain fog and other major problems in POTS and Long COVID. It is detailed just as the pathophysiology that causes it is complex.
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