I Haven't Had the Flu in Years. When I Finally Did, I Used It as a Lab.

Some people get the flu once or twice a year. Some get it 3 or 4 times. They chalk it up to bad luck, a rough winter, or the open-plan office. They take the medication, spend a week on the couch, drag themselves back to work feeling half-dead, and wait for it to happen again.

It is common, but it is not normal.

Common and normal are not the same thing. Getting knocked flat by a respiratory infection 3 or 4 times a year is the average outcome for the average person living with average sleep, average stress management, and average physical condition. You did not get to where you are professionally by benchmarking yourself against average output. You did not build your career by accepting average results as the ceiling. So why are you accepting average immune function as inevitable?

The people around you getting sick every season are not proving that illness is unavoidable. They are showing you what a system under chronic stress looks like from the outside. Frequent illness is a symptom. The cause is upstream — and upstream is exactly where this system can be fixed.

I am not one of those people. For years — long stretches of them — I have not had the flu. Not because I avoid it. I work with teams, I travel, I live in the world. The reason is the same reason I can do things at 44 that I could not do at 34: the system I have built around training, sleep, stress management and nutrition produces a specific output. One of those outputs is a functioning immune system.

So when the flu finally did arrive — and it did, recently, without warning — I was not panicking. I was curious. I had 3 days of fever, the full package of body aches and fatigue, and then a recovery window that I decided to treat as a controlled experiment. I wanted to know exactly what the research said about what I was experiencing, and whether what I instinctively started doing — light cycling when the fever broke, then kettlebells a few days later at reduced load — was backed by anything credible.

It was. And the findings are more interesting than I expected.

Most people reading this are somewhere in the middle. Not sick every month, not immune to everything. You get knocked down a couple of times a year, you do the standard thing — rest, medication, Netflix — and somewhere around day 10 you start wondering whether you should be doing something more useful with your body. Or less. You genuinely do not know. Your doctor says rest. Your inner athlete says train. And you have no framework for deciding.

This article is that framework. What to do during the flu, when to do it, why it matters, and what the science actually says about moving through illness rather than waiting it out.

Your Doctor Is Not Wrong — Just Incomplete

Let me be clear about something before anything else: the general physician who tells you to rest during the flu is not being overcautious. They are being correct. For a specific phase of the illness.

The problem is that most doctors apply that advice like a blanket that covers the entire recovery arc. Day 2 and day 10 get the same prescription: rest. That is where the framework falls apart.

First, a distinction that matters more than most people realize. The flu and the common cold are not the same thing. They share some surface symptoms — congestion, sore throat, fatigue — but influenza is a systemic illness. It hits hard and fast. Fever that comes on in hours, not days. Body aches that feel like you went 10 rounds in a boxing ring. The kind of fatigue where standing up to get a glass of water feels like a project. If you have ever had real influenza, you know exactly what I mean. If you are not sure, you probably had a cold.

This distinction matters because the risk profile during the acute phase of true influenza is different from a head cold. And that risk has a name most people have not heard of: myocarditis.

Myocarditis is inflammation of the heart muscle, and it can be triggered by viral infections — including influenza.¹ The risk is low in absolute terms, but it is not zero, and exercise during the acute febrile phase of flu can increase it. Your heart is already under elevated load during a systemic infection: it is managing fever-driven temperature dysregulation, elevated immune activity and reduced circulating blood volume from dehydration. Add physical exertion on top of that and you are asking a stressed system to do more work than it can safely handle.²

There is also a thermoregulation problem. Fever is your immune system deliberately raising your core temperature to create a hostile environment for the virus. Exercise generates heat. When both are happening simultaneously, your body's ability to regulate temperature becomes compromised — and that is a physiological situation you do not want to be in.³

So when your GP says rest during the flu, they are right. During the acute phase — fever present, systemic symptoms dominant, however many days that takes — rest is not a conservative choice. It is the clinically correct one. Full stop.

The gap in the GP framework is what happens next. Once the fever breaks, once the systemic symptoms begin to lift, the blanket prescription of rest becomes not just unhelpful but actively counterproductive. And that is where the sports medicine perspective enters the conversation.

Your Coach Is Not Wrong Either — Just Reckless

The sports medicine instinct is to get athletes moving again as fast as possible. That instinct is grounded in real science.

Deconditioning happens faster than most people think. A 2016 study from Maastricht University put healthy young males through one week of strict bed rest. The result: 1.4 kilograms of lean tissue lost, a 3.2% decline in quadriceps cross-sectional area, and measurable whole-body insulin resistance — in 7 days.⁴ Another analysis published in the Journal of Applied Physiology found that muscle strength decline follows a logarithmic curve during bed rest, with the steepest losses happening earliest — meaning the first few days of complete inactivity cost you the most.⁵

The NHS states it plainly: as a general rule, it takes twice as long to regain strength as it does to lose it.⁶ Rest for a week, spend 2 weeks earning it back. That is a tax your body charges without asking permission.

For someone who has spent months or years building a training base, this is not an abstract concern. The muscle you have built is not stored permanently. It responds to the signals it receives. Stop giving it the signal to maintain itself and it starts the process of giving it back.

So the sports medicine push to return to movement quickly is not aggressive for its own sake. It is a rational response to a real physiological cost.

Where it becomes reckless is in the application. Elite athletes who push through illness do so with medical supervision, baseline physiological data, and often pharmaceutical support to manage symptoms. They have team doctors monitoring cardiac markers. They have context the average person does not have. When that model gets applied without that infrastructure — when a coach says "push through" and the athlete masks symptoms with NSAIDs to train — the risk profile changes entirely. For a 42-year-old engineering manager with no ECG on record and no medical team on site, that is a different calculation.

The answer is not to choose between the GP's caution and the coach's aggression. The answer is to build a phased protocol that takes both seriously.

The Neck Check Rule — The Bridge Most People Never Learn

Before getting into the protocol, there is one framework from sports medicine that belongs in everyone's toolkit. It is called the neck check rule, and it has been used by sports medicine practitioners for decades.⁷

The principle is simple. Evaluate your symptoms by location.

Above the neck — runny nose, nasal congestion, sneezing, mild sore throat, mild headache — light to moderate movement is generally acceptable in otherwise healthy adults. These symptoms typically indicate an upper respiratory infection that your immune system is managing locally. Gentle movement does not significantly interfere with that process and may modestly support it.

Below the neck — fever, systemic body aches, chest congestion, significant fatigue, productive deep cough — rest is mandatory. These symptoms indicate systemic illness. Your immune system is not just fighting something locally; it is mobilizing across your entire body. Adding physical stress to that load is counterproductive and potentially dangerous.

The neck check rule has one important limitation that I will state explicitly: it was not designed to screen for myocarditis risk. Cardiac inflammation from a viral infection can develop silently — with no obvious chest symptoms — and the neck check gives you no signal for it. If you have had a significant viral illness in the past 2 to 3 weeks and you notice unusual fatigue during exercise, heart rate that feels disproportionately elevated, or any chest discomfort, stop and get it checked.⁸ No training session is worth that risk.

Use the neck check as your daily decision filter during recovery. It is not a substitute for medical assessment, but it is the most practical screening tool available for otherwise healthy adults.

What to Eat During the Flu — and Why Your Grandmother Was Right

Movement protocol aside, what you put into your body during illness matters more than most people treat it. This is not the time for willpower-based fasting or mindless comfort eating. It is the time to feed the system that is working hardest to get you out of this.

Hydration is the non-negotiable

Fever causes significant fluid loss. Your immune system depends on adequate blood volume to circulate white blood cells, cytokines and antibodies to where they are needed. Dehydration slows all of it. Drink water consistently throughout the day. Warm liquids are particularly useful — they thin mucus viscosity, making it easier for your airways to clear the debris the infection leaves behind. This is the same mechanism that aerobic exercise supports. Hot liquids amplify it without requiring you to move.

Hot tea — and why it is not just comfort

Black tea with lemon has been a go-to flu remedy across Eastern Europe for generations. Much of Asia arrives at the same destination differently — green tea, often with ginger or honey, carries its own documented anti-inflammatory mechanism through EGCG rather than theaflavins, but the principle is identical: a hot, polyphenol-rich liquid with immune-supportive additions. It turns out there is actual biology behind both traditions, not just habit.

Black tea contains theaflavins — polyphenolic compounds produced during the fermentation of tea leaves. Research shows theaflavins inhibit pro-inflammatory cytokines and have demonstrated antiviral activity against several respiratory pathogens.⁹ They modulate the NF-κB signalling pathway, one of the primary molecular switches governing the body's inflammatory response.¹⁰ Green tea operates through a similar mechanism via EGCG, for those who prefer it.

Add lemon and you are compounding the effect. Lemon juice provides vitamin C, which supports immune function and has been shown to shorten the duration of upper respiratory infections.¹¹ The peel and pith carry quercetin and hesperidin — flavonoids with anti-inflammatory and antiviral properties that work synergistically with vitamin C, each improving the other's bioavailability.¹² Squeezing lemon into hot tea and letting the peel steep for a minute is not a folk cure dressed up as science. The mechanisms are documented.

Drink 3 to 4 cups throughout the day during the acute phase. Ginger tea, rosehip, and elderberry infusions are useful additions — all carry documented anti-inflammatory or antioxidant properties that support immune function.

The chicken soup question

In 2000, researchers at the Nebraska Medical Center published a study in CHEST that many people dismissed as a joke when they first heard about it: they ran chicken soup through a formal laboratory assay to test its anti-inflammatory properties.¹³

The results were not a joke. Chicken soup significantly inhibited neutrophil chemotaxis — the migration of neutrophils toward the site of infection — in a concentration-dependent manner. In practical terms: it reduced the degree of inflammatory activity in the upper respiratory tract, which is the mechanism behind symptom relief. The effect was not marginal. It was measurable and dose-responsive.

Here is the part that matters for anyone who does not eat chicken: when the researchers tested the vegetables from the soup separately — carrots, celery, onion, parsley, parsnip — they also showed inhibitory activity. The anti-inflammatory mechanism was not exclusive to the chicken. It was distributed across the vegetable components. The broth made from slow-cooking those vegetables carries the same compounds that make the full soup effective.

So the vegetarian version of chicken soup is a rich vegetable broth — onion, garlic, carrot, celery, parsley, a little turmeric and black pepper — simmered long enough to extract everything those vegetables have to offer. It does the same job. The hot liquid thins mucus. The vegetable compounds reduce local inflammation. The salt replaces electrolytes. The warmth is genuinely therapeutic.

Any hot soup works on the liquid mechanics. A miso broth, a lentil soup, a clear vegetable stock — all deliver the hot liquid benefit. The specific anti-inflammatory compounds are highest when you use the vegetables identified in the research: alliums (onion, garlic, leek), root vegetables, and fresh herbs.

What to eat and what to skip

During the acute phase, appetite suppression is normal and partly by design — your body is redirecting energy away from digestion toward immune activity. Do not force large meals. Do prioritize protein even in small amounts: eggs, yogurt, legumes, a protein shake if solid food feels like too much. Your immune system is building antibodies and repairing tissue and it needs amino acids to do it.

Avoid alcohol entirely — it suppresses immune function, disrupts sleep architecture and dehydrates you at exactly the moment your body can least afford any of those things. Avoid heavily processed, high-sugar foods for the same reason: they drive insulin spikes that temporarily impair white blood cell function.

As you move into the recovery phases and appetite returns, increase protein priority. Muscle repair and immune recovery share the same substrate. Eating enough protein in the second week of recovery is as important as the training you are doing.

The Protocol — Phase by Phase

This is what I did. This is also what I recommend to my coaching clients when they get sick. It is grounded in the research, adapted for real people with training bases worth protecting.

Phase 1 — Days 1 to 4: Absolute Rest

Fever is present. This phase is not negotiable.

The only variables you control here are hydration, sleep and nutrition. Get as much sleep as your body will take. Hydrate aggressively — fever drives significant fluid loss and you need that volume to support immune function and waste clearance. Eat enough protein to give your immune system the amino acids it needs to build antibodies and repair tissue, even if your appetite is suppressed.

That is it. No training. No "light movement to stay active." If you can walk slowly to the kitchen and back without feeling worse, that is acceptable. Structured exercise of any kind is not.

The reason this phase feels like doing nothing is because your body is doing everything. The fever is deliberate. The fatigue is your immune system pulling energy away from your muscles and directing it at the virus. Respect that process. You are not losing fitness — you are investing in getting out of this faster.

Phase 2 — Days 5 to 7: The Fever Breaks, Movement Begins

The signal to start moving: no fever for at least 24 consecutive hours and a genuine, if modest, return of energy. Not absence of symptoms — just absence of fever and the first signs that the acute phase has passed.

This is when I got on the bike. I have a bike, I like cycling, and at low intensity it is an extremely low-impact way to generate the aerobic stimulus you need here. If you do not have a bike, walk. Go outside if you can — fresh air, natural light, and a change of environment all support recovery. Start at a comfortable pace and see how you feel. If you can walk a little faster after 10 minutes without it costing you, try it. Your body will tell you clearly if you have gone too far.

The reason aerobic movement is specifically useful at this stage goes beyond "movement is good." It comes down to mucociliary clearance. Exercise increases ventilation rate and respiratory airflow. That increased airflow physically assists the body in mobilizing and clearing mucus from the airways.¹⁴ The coughing and sneezing that aerobic activity tends to provoke is not a side effect — it is the mechanism. You are helping your respiratory system do what it is already trying to do, faster.

Research on aerobic exercise and mucociliary function shows that exercise increases the release of adrenergic mediators that alter mucus viscosity and accelerate ciliary transport velocity.¹⁵ In plain language: movement helps your body clear the debris left behind by the infection more efficiently.

Keep the intensity low enough that you could hold a conversation throughout. Heart rate well below your normal training zones. If you feel significantly worse during or after — spike in fatigue, unusually elevated heart rate for the effort level, any chest symptoms — stop immediately and go back to Phase 1. The neck check applies at every session.

Start with 15 minutes on day 1 of this phase. If you feel fine the next day — not just tolerable, actually fine — extend to 20. Build day by day from there. Do not front-load the volume. The goal is a positive signal each session, not a distance target.

Phase 3 — Days 7 to 10: Reintroducing Resistance

The signal to add resistance work: above-neck symptoms only, energy substantially restored, 2 or more days of Phase 2 movement completed without negative response.

This is when I picked up the kettlebells. Not my normal working weight — approximately 60 to 70% of it. And not to failure. The goal is not training stimulus. The goal is hormonal and systemic support.

Moderate resistance training triggers a meaningful hormonal response. Testosterone and growth hormone both increase acutely in response to compound resistance work.¹⁶ Both support tissue repair and immune modulation. The IL-6 response from muscle contraction — often misread as purely inflammatory — has important anti-inflammatory downstream effects when produced by muscle tissue rather than fat tissue, promoting the release of IL-10 and IL-1ra which help regulate and resolve inflammation.¹⁷

In other words: a moderate kettlebell session at this stage is not just maintaining muscle. It is producing hormonal signals that actively support recovery.

What to avoid: training to failure, high-intensity circuits, anything that drives significant cortisol elevation. High cortisol suppresses immune function — the opposite of what you need right now.¹⁸ Keep sessions submaximal. The Grease the Groove approach works well here — not as a metaphor for shorter sessions, but literally: a single set, done well, stopped before it gets hard. That is a valid session at this stage.

Start with 5 minutes of work. A few swings, a few presses, a few squats. That is enough to produce the hormonal signal you are after without overloading a system still in recovery. Build from there day by day. Cap at 20 minutes total until you feel genuinely like yourself again — not "better than yesterday" but actually normal. When you hit that, you are ready for Phase 4.

Phase 4 — Days 10 to 14: Graduated Return

If the previous phases have gone cleanly, you are ready to resume normal training — but not at normal volume immediately.

Start at 70 to 80% of your pre-illness training load. Monitor your resting heart rate: if it is elevated by more than 5 to 7 beats above your baseline, pull back. Your body is still completing its recovery even if you feel fine subjectively, and elevated resting HR is one of the clearest signals that the system is still under stress.

After 2 consecutive sessions that feel genuinely normal — not "fine considering" but actually normal — you are back. Full volume. Full intensity. The experiment is complete.

One rule that applies across every phase of this protocol: if at any point you experience a return of fever, a spike in fatigue that feels disproportionate to the effort, or heart rate that is running significantly higher than you would expect for the intensity — stop immediately. Do not push through. Rest for at least 24 hours before attempting any movement again. If symptoms have worsened rather than stabilized after that rest period, go back to Phase 1 and treat it as a reset. The protocol is not a schedule to keep. It is a framework that follows your body's signals — not the other way around.

Getting Sick 4 Times a Year Is Not Bad Luck — It Is a System Readout

I want to come back to where this article started, because it is the part that matters most for a specific group of people reading this.

If you are getting the flu or a significant respiratory illness 3 to 4 times a year, that frequency is a readout. Not bad luck. Not genetics. Not the season. A readout of the system you are running.

You optimized your way to a senior role in one of the most demanding industries on the planet. You did not do that by accepting the average person's results as the benchmark. Getting sick 4 times a year is the average person's result. It is not yours to keep.

Chronically elevated cortisol — the kind produced by sustained overwork, fragmented sleep, and the particular cognitive load that comes with senior roles in tech — directly suppresses immune function. Cortisol reduces natural killer cell activity, impairs antibody production, and reduces the body's inflammatory response to new infections.¹⁹ This is not a minor effect. Sustained cortisol elevation measurably degrades the immune system's ability to detect and respond to pathogens.

Layer sedentary behavior on top of that. Regular moderate-intensity exercise is one of the most consistently documented immune system supports in the research literature. Adults who walked at least 20 minutes a day, 5 days a week had 43% fewer sick days than those who exercised once a week or less, and when illness did occur, symptoms were milder and recovery faster.²⁰ The mechanism is direct: moderate aerobic activity increases circulation of neutrophils, natural killer cells, T cells and anti-inflammatory cytokines.²¹ Stop exercising consistently and that immune surveillance degrades.

Add poor sleep — the kind that happens when you are pushing through high-demand work cycles on 5 or 6 hours a night. Sleep is when immune memory is consolidated and cytokine production is regulated. Chronic sleep restriction measurably reduces vaccine response and increases infection susceptibility.²²

This is the exact profile of the senior tech professional I work with most often. High cognitive load. Low physical load. Fragmented sleep. Sustained stress with no reliable recovery mechanism. And a pattern of illness that they have normalized because everyone around them seems to have the same pattern.

They do not have to. The pattern is upstream of the flu. Fix the upstream conditions and the downstream output changes.

I have not had the flu in years — not because I have unusual genetics, but because the system I run produces a specific immune output. That system is trainable. It is buildable. And it is exactly what I work on with clients in the first 90 days of coaching.

If you recognize your pattern in what I have described — getting sick repeatedly, recovering slowly, feeling like you never quite get back to full capacity before the next thing arrives — that is worth a conversation. Book a free 30-minute strategy call.

The Bottom Line

The flu will come. That is not the question.

The question is whether you move through it or just wait it out. The evidence is clear: passive bed rest until fully recovered costs more than it saves. The muscle loss is real, the deconditioning is real, and the recovery from the inactivity adds weeks to the timeline that the illness itself created.

The answer is not to train through it either. The acute phase is the acute phase. Respect it completely.

The answer is a protocol. Respect the fever phase absolutely. Move the moment it breaks — carefully, at low intensity, with your body as the signal. Add resistance work when the systemic symptoms are gone. Rebuild progressively and monitor the signals your body gives you.

This is what I did. This is what the research supports. And this is what I tell every client who messages me at day 3 of the flu asking what they should do.

Get through the fever. Then get back to work.