Can I exercise with the flu?

Why should I rest instead of working out with the flu?

The NHS advice for treating flu at home is simple: rest and sleep, and drink plenty of water to avoid dehydration. Paracetamol (acetaminophen) or ibuprofen can bring down a fever and ease aches. A workout is not on that list.

Flu is not the same as a mild cold. The CDC says flu usually starts suddenly, with fever or chills, cough, sore throat, body aches, headache and tiredness. Fever with flu commonly lasts 3 to 4 days. Most people recover in a few days to less than 2 weeks.

Dehydration is a practical reason to hold off. The NHS lists a high temperature and sweating a lot after exercise as 2 separate causes of dehydration. Exercising with a fever stacks both.

• Fever, chills or body aches: rest
• Fever gone but you still feel wiped out: keep resting, because the CDC rule is about symptoms improving overall, not just the fever
• Fever-free for 24 hours without medicine and clearly improving: you can start thinking about light exercise

Can I go to the gym or team practice with the flu?

Not yet. The CDC says that when you are sick with flu, you should stay home and away from other people, including people you live with who are not sick.

You can go back to normal activities, which includes the gym, once both of these have been true for at least 24 hours: your symptoms are getting better overall, and you have not had a fever without using fever-reducing medicine. Taking ibuprofen or acetaminophen to hide a fever does not count.

For the next 5 days after you go back, the CDC asks you to take added precautions, like cleaner air, good hygiene such as washing your hands, a well-fitting mask, keeping more distance from others, or testing. In a busy gym, that could mean wiping down equipment and skipping the crowded class for a few more days. The NHS says you are most likely to spread flu in the first 5 days after getting infected.

How do I get back to exercise after the flu?

None of the CDC, NHS or MedlinePlus pages we used give a set day-by-day plan for returning to exercise after flu. What they do give is the starting line: improving overall and 24 hours fever-free without medicine.

From there, a sensible approach is to start well below your usual effort and let how you feel guide the next step. A walk before a run, a short session before a long one. If an easy session leaves you much more tired, short of breath or achy than it should, take that as a sign to rest a few more days.

• Drink first: the NHS says to drink fluids if you have signs of dehydration, like thirst or dark yellow pee, and to avoid caffeine and alcohol, which both dehydrate you
• Keep it short and easy for the first sessions back
• If a fever comes back or you feel worse, the CDC says to stay home again until you are improving and 24 hours fever-free without medicine

Why do chest pain or palpitations after the flu matter?

The CDC lists inflammation of the heart, called myocarditis, among the serious complications flu can trigger. It is one reason not to push through new symptoms during a workout.

MedlinePlus says myocarditis is most often caused by an infection that reaches the heart, and names the flu virus as one cause. Its symptoms include chest pain that can feel like a heart attack, fainting (often linked to an irregular heart rhythm), shortness of breath and a fast heart rate. MedlinePlus says to contact your provider if you have these symptoms, especially after a recent infection.

Palpitations on their own are common and usually not serious, according to the NHS, and strenuous exercise is one ordinary trigger. What changes the picture is palpitations together with chest pain, shortness of breath or feeling faint.

• Stop exercising if you get chest pain, a pounding or irregular heartbeat that does not settle, dizziness or fainting, or breathlessness that is out of proportion to the effort
• Do not restart until you have been checked by a clinician

Who should check with a clinician before exercising after the flu?

The CDC says some people are at higher risk of serious flu complications, including adults 65 and older, pregnant people, children younger than 5, and people with long-term conditions such as asthma, diabetes or heart disease. The NHS says to get advice urgently if you are 65 or older, pregnant or recently gave birth, have a long-term condition, or have a weakened immune system.

If you are in one of those groups, it is worth asking before you start training again, especially if you have a heart condition. The NHS also says to get advice if flu symptoms are not improving after 7 days.