How to Pace with Long COVID: Avoiding the Push-Crash Cycle

The Reality of the Boom and Bust Cycle

Managing Long COVID requires a radical shift in how patients view energy, exertion, and recovery. Because Long COVID frequently involves a dysfunction in how the body's cells produce energy, traditional recovery methods are not only ineffective but can be actively harmful. The unpredictable nature of Long COVID energy levels often traps patients in a debilitating pattern known as the boom and bust cycle. On a "good day" when energy levels feel slightly higher, patients naturally want to catch up on backlogged tasks, whether that means chores, work, socializing, or light exercise. This is the "boom" phase, driven by a desperate desire to return to normalcy and productivity.

However, by attempting to catch up, the patient inadvertently exhausts their compromised aerobic energy system. Because the body's cellular batteries cannot recharge normally, this overexertion triggers a massive systemic backlash. 12 to 48 hours later, this triggers the "bust" phase, flattening the patient with profound exhaustion and forcing a period of prolonged, enforced bed rest until they stabilize. This cycle hinders systemic healing, continuously stresses the cellular energy system, and steadily lowers the patient's overall baseline of health over time. Breaking this cycle is the absolute foundation of Long COVID rehabilitation.

Understanding Post-Exertional Malaise (PEM)

At the core of the boom and bust cycle is a physiological phenomenon called post-exertional malaise (PEM), sometimes referred to as post-exertional symptom exacerbation (PESE). PEM is a hallmark symptom of both Long COVID and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), affecting an estimated 50% to 80% of Long COVID patients. Unlike typical fatigue that improves with a good night's sleep, PEM is a disproportionate, multi-systemic worsening of symptoms that occurs after even minor physical, cognitive, or emotional exertion. It is a defining feature that separates Long COVID fatigue from standard post-viral tiredness, as noted by the World Health Organization and leading physiotherapists.

One of the most insidious aspects of PEM is its delayed onset. A patient might exert themselves on a Monday, feel relatively fine on Tuesday, and then experience a catastrophic crash on Wednesday. This 12-to-48-hour delay makes it incredibly difficult for patients to identify exactly which activity triggered their symptoms, leading to confusion, frustration, and a constant fear of movement. During a PEM crash, patients frequently report severe cognitive dysfunction (brain fog), neuropathic pain, shortness of breath, and a profound, heavy exhaustion that feels as though their limbs are made of lead. Recognizing and respecting the reality of PEM is the first and most crucial step in learning how to pace effectively.

The Concept of the Energy Envelope

To successfully manage Long COVID and avoid the devastating consequences of PEM, patients and specialized occupational therapists utilize the concept of the "energy envelope." You can think of the energy envelope as a strict, non-negotiable daily budget of cellular energy. Before COVID-19, your energy envelope was likely vast and elastic; you could push yourself through a long workday, go to the gym, and still have energy to socialize, with your body quickly replenishing its reserves overnight. Now, that envelope is drastically shrunken and rigid. If you spend more energy than you have in your daily envelope, you will inevitably trigger a PEM crash, as highlighted by researchers studying energy-limiting conditions.

Staying within the energy envelope requires a radical shift in how you view daily activities. It means recognizing that every single action—whether it is taking a shower, digesting a heavy meal, having an emotional conversation, or simply sitting upright at a desk—draws from the exact same, limited pool of energy. Pacing is the active, intentional practice of monitoring your energy expenditure to ensure you never cross the boundary of your envelope. By consistently staying within this safe zone, you avoid the cellular damage associated with crashes, stabilize your nervous system, and create an environment where your body can slowly begin to recover and expand its capacity over time.

Mitochondrial Dysfunction and Energy Failure

To understand why pacing is so critical, we must look at what is happening inside the cells of Long COVID patients. The exhaustion experienced in Long COVID is not caused by laziness, psychological blockages, or mere physical deconditioning. Instead, it is driven by profound, measurable biological abnormalities. A landmark 2024 study published in Nature Communications by Appelman, Wüst, and colleagues investigated the cellular effects of exertion by taking skeletal muscle biopsies from Long COVID patients before and after a 15-minute cycling test. The findings were revolutionary and validated what patients had been reporting for years.

The researchers discovered that the mitochondria—the microscopic powerhouses responsible for producing adenosine triphosphate (ATP), the body's primary energy currency—were physically deranged and functioning poorly in Long COVID patients. Following mild exertion, the mitochondria failed to scale up energy production to meet the body's demands. Furthermore, the exertion triggered severe, immediate exercise-induced myopathy (muscle damage), localized tissue inflammation, and the accumulation of amyloid-containing deposits within the skeletal muscles. This proves that pushing a Long COVID patient to exercise does not build strength; it actively damages their cellular infrastructure and harms their mitochondria.

Endothelial Damage and Oxygen Starvation

Beyond the mitochondria, Long COVID severely impacts the vascular system, further explaining the necessity of pacing. Research led by Dr. David Systrom and the Open Medicine Foundation utilizing invasive cardiopulmonary exercise testing (iCPET) has highlighted that Long COVID patients suffer from severely impaired oxygen transport. During physical exertion, the heart pumps oxygen-rich blood to the muscles. However, in Long COVID, endothelial dysfunction—meaning the blood vessels are inflamed, inflexible, or blocked by microclots—hinders the muscles from properly extracting that oxygen from the bloodstream.

Additionally, invasive testing frequently shows cardiac preload failure, meaning not enough blood returns to the heart during exertion. Because the muscles are starved of oxygen, the body is forced into a state of systemic hypoxia even during mild activities like walking up a flight of stairs. This oxygen starvation is a primary driver of the shortness of breath, heavy limbs, and racing heart rates that patients experience when they step outside their energy envelope. Pacing is therefore a strategy designed to keep the body's oxygen demands low enough that the damaged vascular system can actually meet them without failing.

The Danger of the Anaerobic Threshold

Because Long COVID patients cannot efficiently use oxygen to make energy (aerobic metabolism), their bodies are forced to switch to a backup system called anaerobic metabolism. In a healthy person, the body only switches to anaerobic metabolism during intense, high-effort exercise, like sprinting or heavy weightlifting. This backup system is fast but highly inefficient, producing toxic byproducts like lactic acid that cause muscle burn and fatigue. The point at which the body switches from aerobic to anaerobic energy production is called the Ventilatory or Anaerobic Threshold (AT).

In Long COVID and ME/CFS, the anaerobic threshold is severely lowered. A Long COVID patient might cross their anaerobic threshold simply by standing up to brush their teeth or walking to the mailbox. When they cross this threshold, their body floods with lactic acid and oxidative stress, triggering the systemic inflammation cascade that results in a PEM crash. The entire scientific premise of pacing and heart rate monitoring is to identify this lowered anaerobic threshold and strictly govern daily activities to ensure the patient remains in an aerobic state, thereby avoiding the toxic metabolic fallout of anaerobic energy production.

Step 1: Establish Your Baseline and Radical Rest

The first step in implementing a successful pacing strategy is establishing your true baseline. Your baseline is the amount of activity you can sustain every single day without triggering any worsening of symptoms or post-exertional malaise. For many Long COVID patients trapped in the boom and bust cycle, finding this baseline requires a period of "radical rest." Radical rest means stripping away all non-essential activities, obligations, and stressors to allow your chronically inflamed nervous system to calm down. It involves resting aggressively until your daily symptoms stabilize at a manageable level.

During this initial phase, it is crucial to understand that cognitive and emotional exertion drain the energy envelope just as quickly as physical exertion. Watching television, scrolling through social media, reading a book, or having a stressful conversation all require significant cellular energy. True radical rest often involves lying flat in a dark, quiet room with an eye mask and earplugs, practicing deep diaphragmatic breathing to signal safety to your autonomic nervous system. Only once you have stabilized your symptoms through radical rest can you begin to accurately assess what your true daily energy envelope looks like.

Step 2: Calculate Your Safe Heart Rate Limit

Because subjective feelings of fatigue are often unreliable—especially when you are used to pushing through pain—objective data is essential for pacing. Heart rate monitoring (HRM) is the gold standard for staying within your energy envelope. By tracking your heart rate, you can ensure you do not cross your lowered anaerobic threshold. The Workwell Foundation, a leader in ME/CFS and Long COVID exercise physiology, recommends a specific formula for patients who do not have access to specialized cardiopulmonary exercise testing (CPET).

To find your safe limit, you must first calculate your Resting Heart Rate (RHR) by taking a 7-day average of your heart rate immediately upon waking, while still lying in bed. Once you have your RHR, you simply add 15 beats per minute (bpm) to that number. For example, if your resting heart rate is 70 bpm, your absolute maximum heart rate limit for daily activities should be 85 bpm. You then set an alarm on a smartwatch or chest strap monitor to alert you if your heart rate exceeds 85 bpm. If the alarm sounds, you must immediately stop what you are doing, sit or lie down, and wait for your heart rate to return to baseline before continuing.

Step 3: Apply the Traffic Light System

To make daily decision-making easier when dealing with cognitive fatigue and brain fog, occupational therapists recommend using the Traffic Light System to categorize your symptoms and activities. This visual framework helps you quickly assess whether it is safe to proceed with a task or if you need to stop and rest. The Green Zone represents your safe baseline: your symptoms are low, your heart rate is stable, and you are comfortably within your energy envelope. In this zone, it is safe to perform gentle, planned activities while continuing to monitor your body.

The Yellow (or Amber) Zone is your critical warning area. In this zone, you might notice a slight increase in your heart rate, a subtle thickening of brain fog, a feeling of heaviness in your limbs, or a mild headache. This is your body's check-engine light turning on. When you enter the Yellow Zone, you must immediately slow down, modify the task (e.g., sit down instead of standing), or stop entirely to rest. The Red Zone indicates that you have crossed your threshold and are entering a crash. In the Red Zone, all activity must cease, and you must engage in aggressive, low-sensory rest to mitigate the severity of the impending PEM flare-up.

Step 4: Break Tasks into Micro-Chunks

Once you understand your heart rate limits and the traffic light system, you must apply them to your daily life by breaking tasks into micro-chunks. Healthy individuals view taking a shower as a single, simple task. For a Long COVID patient, a shower is a complex, high-energy marathon involving standing, heat exposure, raising arms above the head, and sensory input. To pace a shower, you must break it down: gather your clothes and rest for 10 minutes; sit on a shower stool while washing; turn off the water and rest in a terrycloth robe instead of actively towel-drying; lie down for 30 minutes afterward.

This micro-chunking applies to every aspect of life. If you need to chop vegetables for dinner, do it sitting at the kitchen table in the morning, rest for several hours, and then cook them later in the day. If you need to read an important document, read for 10 minutes, close your eyes and practice deep breathing for 5 minutes, and then resume. By proactively inserting rest periods before you feel exhausted, you keep your heart rate from spiking and keep your body safely within its aerobic energy limits, effectively flattening the boom and bust cycle.

The Trap of Graded Exercise Therapy (GET)

One of the most dangerous mistakes a Long COVID patient can make is attempting Graded Exercise Therapy (GET). For decades, GET was the standard approach to managing chronic fatigue, operating on the assumption that patients were simply deconditioned and needed to slowly increase their exercise tolerance. However, as researchers and advocacy groups have emphatically proven, GET is actively harmful for anyone experiencing post-exertional malaise. Because Long COVID involves severe mitochondrial dysfunction and endothelial damage, pushing the body to exercise harder does not build stamina; it destroys cellular infrastructure and triggers massive inflammatory cascades.

Many well-meaning doctors, physical therapists, and family members may encourage you to "push through" the fatigue, believing that a little bit of sweat will help clear your system. Yielding to this pressure is a critical pitfall. Early overexertion can severely prolong and worsen Long COVID symptoms, potentially lowering your baseline permanently. It is vital to advocate for yourself, refuse therapies that encourage pushing through pain, and educate your care team that your fatigue is a physiological energy failure, not a psychological barrier or a lack of fitness.

Ignoring Cognitive and Emotional Exertion

A very common mistake when learning to pace is focusing entirely on physical movement while completely ignoring cognitive and emotional exertion. Patients often meticulously track their steps and heart rate but fail to account for the massive amount of energy required by the brain. The brain is an incredibly energy-hungry organ, consuming roughly 20% of the body's total energy output. Tasks like reading complex emails, balancing a budget, engaging in an intense conversation, or even watching a fast-paced movie can rapidly deplete your energy envelope and trigger a severe PEM crash, even if you haven't left your bed.

Emotional exertion is equally draining. The stress of navigating the medical system, grieving the loss of your pre-illness life, dealing with financial anxiety, or arguing with a partner floods the body with adrenaline and cortisol. This sympathetic nervous system activation burns through cellular energy at an astonishing rate. To pace effectively, you must budget for cognitive and emotional tasks just as strictly as you budget for physical tasks. If you have a stressful doctor's appointment on Tuesday, you must plan for aggressive cognitive rest on Monday and Wednesday to balance the energetic cost.

Reactive Resting Instead of Proactive Resting

Perhaps the most difficult habit to break is the tendency to rest reactively rather than proactively. In our pre-illness lives, we were taught to work until we felt tired, and then take a break. In the context of Long COVID and the boom and bust cycle, waiting until you feel tired to rest is a catastrophic error. By the time you feel the heavy, aching exhaustion of Long COVID, you have already crossed your anaerobic threshold, breached your energy envelope, and triggered the metabolic cascade that leads to a PEM crash. The damage has already been done.

Successful pacing requires proactive resting. This means scheduling mandatory rest breaks before you feel any symptoms of fatigue. If you know that standing in the kitchen for 15 minutes usually triggers your symptoms, you must proactively sit down and rest after 10 minutes, while you still feel perfectly fine. This requires immense discipline, as it feels counterintuitive to stop an activity when you feel capable of continuing. However, proactive resting is the only way to keep your heart rate stable, avoid lactic acid buildup, and maintain a steady, sustainable baseline of energy throughout the day.

Misunderstanding What "Rest" Actually Means

Another major pitfall is misunderstanding the definition of rest. When told to rest, many patients will lie on the couch and scroll through social media, watch a documentary, listen to a podcast, or text their friends. While these activities involve physical stillness, they are highly stimulating to the brain and the nervous system. The visual input from a screen, the cognitive processing of language, and the emotional reactions to social media all require significant ATP energy production. This is not true rest; it is simply a different form of exertion.

For a Long COVID patient, true restorative rest—often called "radical rest" or "aggressive rest"—requires minimizing all sensory input. It involves lying completely flat (to relieve the heart from the burden of pumping blood against gravity, which is crucial for those with dysautonomia or POTS), closing your eyes, wearing an eye mask, using earplugs or noise-canceling headphones, and practicing slow, diaphragmatic breathing. This low-sensory environment signals to your autonomic nervous system that you are safe, allowing it to shift out of a "fight or flight" state and into a "rest and digest" state where cellular repair can actually occur.

The Visible App: Built for Illness, Not Fitness

Because standard fitness trackers (like Apple Watches or Fitbits) are designed to push healthy people to "close their rings" and achieve 10,000 steps a day, they can be incredibly dangerous for Long COVID patients. To fill this gap, a new ecosystem of specialized tools has emerged, led by the Visible app. Developed by an engineer living with Long COVID, Visible is a pacing app explicitly designed for energy-limiting chronic illnesses like ME/CFS, POTS, and Long COVID. It flips the traditional fitness model upside down, actively encouraging users to rest and conserve energy rather than push themselves.

Visible works by measuring your Morning Stability Score. Upon waking, users place their finger over their smartphone camera to measure their Resting Heart Rate (RHR) and Heart Rate Variability (HRV). Combined with sleep data, the app generates a score from 1 to 5 that dictates your safe energy budget for the day. The premium version, Visible Plus, includes a specialized Polar armband that provides continuous, real-time heart rate monitoring. It tracks "PacePoints" throughout the day and sends immediate notifications to your phone when you are overexerting, allowing you to stop and rest before triggering a crash. It also tracks postural changes, making it an invaluable tool for managing comorbid dysautonomia.

Heart Rate Monitors and Chest Straps

For patients utilizing the Workwell Foundation's heart rate pacing formula (RHR + 15 bpm), accurate real-time data is non-negotiable. While wrist-based smartwatches are convenient, they often suffer from lag during sudden heart rate spikes, which are common in Long COVID patients with dysautonomia. Therefore, many pacing experts recommend using a dedicated chest strap monitor, such as the Polar H10 or the Garmin HRM-Pro. These devices measure the electrical activity of the heart directly, providing instantaneous, highly accurate readings that allow you to catch an anaerobic spike the exact second it happens.

If a chest strap is too uncomfortable for daily wear—a common issue for patients with sensory sensitivities or costochondritis—smartwatches can still be highly effective if configured correctly. Apps like "Pace Me" or "Hype" can be installed on Apple Watches or Garmins to set strict, customized heart rate alarms. The key is to manually disable all fitness goals, stand reminders, and calorie-burning notifications on these devices. You must transform the device from a fitness coach into a strict energy auditor, ensuring it only alerts you when you are in danger of breaching your energy envelope.

Heart Rate Variability (HRV) Tracking

In addition to monitoring raw heart rate, tracking Heart Rate Variability (HRV) is a powerful tool for Long COVID pacing. HRV measures the variance in time between your heartbeats, providing a direct window into the state of your autonomic nervous system. A high HRV generally indicates that your body is relaxed, recovered, and in a parasympathetic (rest and digest) state. A low HRV indicates that your body is under severe stress, inflamed, and stuck in a sympathetic (fight or flight) state. For Long COVID patients, a sudden drop in morning HRV is often the very first warning sign of an impending PEM crash.

Free or low-cost apps like Elite HRV or HRV4Training allow patients to measure their daily HRV using a smartphone camera or a compatible chest strap. By taking a two-minute reading every morning, you can objectively assess your nervous system's readiness for the day. If your HRV is significantly lower than your baseline, it is a clear, biological mandate to drastically reduce your energy envelope for that day, cancel non-essential plans, and engage in radical rest. This objective data is incredibly validating, helping patients trust their bodies and make difficult pacing decisions without guilt.

Clinical Frameworks and Advocacy Resources

Navigating Long COVID pacing can be overwhelming, but there are robust clinical and advocacy resources available to guide you. The Workwell Foundation provides extensive, free educational materials on the science of post-exertional malaise, how to calculate your safe heart rate threshold, and how to communicate your limitations to medical professionals. Their research is foundational to the modern understanding of energy-limiting illnesses and provides the scientific backing needed to push back against harmful exercise recommendations.

Additionally, organizations like Long COVID Physio, an international, patient-led association of physiotherapists living with Long COVID, offer peer-reviewed resources, video guides, and advocacy tools centered firmly around pacing and avoiding graded exercise therapy. The ME Association also provides comprehensive PDF guidebooks on pacing, the energy envelope, and symptom tracking. Utilizing these resources can help you build a scientifically sound pacing protocol, connect with validating communities, and equip yourself with the knowledge needed to advocate for appropriate, evidence-based care in clinical settings.

The PACELOC Trial and Crash Reduction

The efficacy of pacing is not just anecdotal; it is heavily supported by emerging clinical trials focused on Long COVID rehabilitation. One of the most significant studies is the PACELOC trial conducted by the University of Leeds in 2022. This prospective cohort study evaluated an 8-week supervised pacing protocol utilizing the World Health Organization (WHO) Borg CR-10 pacing scale. The trial involved 31 participants who had been suffering from long-standing Post-COVID Syndrome for an average of 17 to 29 months, a demographic for whom spontaneous recovery is statistically rare.

The data from the PACELOC trial yielded highly impressive and validating results. Prior to the study, the participants averaged 3.4 severe PEM "crashes" per week, keeping them trapped in a constant state of relapse and suffering. By strictly adhering to the structured pacing protocol and utilizing active rest techniques, the patients successfully reduced their crashes to an average of just 1.1 per week by the end of the program. The frequency, severity, and duration of their post-exertional symptom exacerbation episodes decreased by roughly 15% each week. Furthermore, their overall health status scores improved significantly, proving that disciplined pacing directly stabilizes the condition and improves quality of life.

The 2025 Clague-Baker Feasibility Study on Wearables

Recent research has also validated the use of digital tools and heart rate monitors for managing the energy envelope. A landmark October 2025 feasibility study published in Fatigue: Biomedicine, Health & Behavior by Clague-Baker et al. evaluated the use of heart rate monitoring (HRM) for pacing in ME/CFS and Long COVID patients. The study aimed to determine if patients could successfully integrate objective biometric data into their daily lives to avoid overexertion and manage their complex symptoms.

The findings confirmed that HRM is a highly acceptable, feasible, and effective self-management tool. Follow-up data showed incredible patient adherence, with 89% of participants continuing to use their heart rate monitors at 8 weeks, and 66% still using them after 6 months. Patients reported that the heart rate monitors provided the objective biofeedback necessary to stay within safe exertion limits, effectively taking the guesswork out of pacing. The intervention group showed positive increases in physical health, emotional well-being, and overall energy levels, demonstrating that wearable technology is a crucial component of modern Long COVID rehabilitation.

Cardiopulmonary Exercise Testing (CPET) Evidence

The biological necessity of pacing is perhaps most starkly proven by 2-day Cardiopulmonary Exercise Testing (CPET) data. CPET is the gold standard for measuring how the body's cardiovascular and pulmonary systems respond to exertion. When healthy individuals perform a maximum-effort CPET on two consecutive days, their performance on day two is virtually identical to day one. Their bodies recover overnight, and their aerobic capacity remains stable. This is the normal physiological response to exercise.

However, when Long COVID and ME/CFS patients undergo a 2-day CPET, the results are drastically different. As documented by researchers at the Workwell Foundation and the National Institutes of Health, a Long COVID patient's performance on day two plummets significantly. Their volume of oxygen consumed (VO2 max), workload capacity, and anaerobic threshold all drop dramatically compared to day one. This objective data unequivocally proves the physiological reality of post-exertional malaise. It demonstrates that exertion actively damages the patient's cellular energy system rather than reconditioning it, providing irrefutable clinical evidence that pacing is a biological necessity, not a psychological choice.

Redefining Progress and Success

The path forward with Long COVID requires a profound psychological shift in how you define progress and success. In a healthy body, progress is linear and additive: you run a little further, lift a little heavier, or work a little longer each day. In the context of Long COVID, progress is defined by stability. Success is not necessarily doing more today than you did yesterday; success is making it through the week without triggering a severe PEM crash. By flattening the boom and bust cycle through meticulous pacing, you are giving your nervous system the safety and consistency it desperately needs to begin the slow process of cellular repair.

It is essential to practice immense self-compassion during this journey. Grieving the loss of your pre-illness capacity is a normal and necessary part of living with a complex chronic illness. Acknowledge that your profound exhaustion and cognitive fog are not character flaws, signs of laziness, or a lack of willpower; they are the direct results of a measurable cellular energy crisis. By validating your own experience and strictly enforcing your energy envelope, you are taking the most powerful, evidence-based step possible toward reclaiming your quality of life.

Integrating Medical Support and Supplements

While pacing is the foundational behavioral strategy for managing Long COVID, it is most effective when combined with targeted medical support. Because Long COVID involves severe oxidative stress and mitochondrial dysfunction, many patients explore integrative interventions designed to support cellular energy production and reduce neuroinflammation. For example, ubiquinol (CoQ10) is frequently utilized to support the mitochondrial electron transport chain, potentially helping cells produce ATP more efficiently. Similarly, magnesium citrate is often explored to help manage fatigue and support muscle function in patients dealing with chronic pain and tension.

Furthermore, multidisciplinary clinics are increasingly utilizing targeted pharmacological options to address specific, overlapping symptoms that drain the energy envelope. Medications to manage dysautonomia and POTS (like beta-blockers or ivabradine), management strategies for mast cell activation syndrome (MCAS), and therapies aimed at reducing micro-clotting can all help lower the overall burden on your body. By addressing these physiological roadblocks medically, you can effectively expand your energy envelope from the inside out, making your pacing efforts significantly more effective.

Building a Sustainable Future

Living with Long COVID is an undeniable challenge, but with the right tools, knowledge, and support, it is possible to build a sustainable and meaningful life. Pacing is not a prison sentence; it is a blueprint for survival and eventual stabilization. By utilizing heart rate monitors, embracing the traffic light system, and respecting the biological reality of post-exertional malaise, you can break free from the devastating boom and bust cycle. As the scientific community continues to unravel the mechanisms of this disease through massive trials like RECOVER, the protocols for managing Long COVID will only continue to improve.

If you are struggling to manage your Long COVID symptoms, establish a safe pacing baseline, or navigate the complexities of post-exertional malaise, you do not have to do it alone. Specialized medical care that understands the intricacies of energy-limiting chronic illnesses is crucial. Explore RTHM's clinical services and Long COVID care options to connect with providers who validate your experience and can help you build a comprehensive, personalized management plan. Always consult with a dysautonomia-literate or Long COVID-literate healthcare provider before starting or stopping any medication, supplement, or physical rehabilitation protocol.