Exercise makes you feel good and helps keep you healthy, but nothing can sideline you faster than a bout of the flu. The flu is a respiratory illness often accompanied by congestion and trouble breathing.
Under these conditions, you generally shouldn't exercise or do anything that makes you breathe hard. If your flu symptoms are mild, use common sense when it comes to exercise. Don't push yourself too hard and give your body time to heal. If your symptoms are severe or you have a compromised immune system, see a medical professional for treatment and to discuss exercise options.
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If you have the flu, it's probably a good time to take a rest day (or week). You absolutely should not exercise when you have the flu if you have a fever, but with all other symptoms, at least cut back on your intensity and duration.
What Is Influenza?
Influenza is caused by a virus that can cause fevers, stuffy nose, coughs, chills, sore throats and muscle aches, among other things, says Harvard Health Publishing. While some of the symptoms resemble those of the common cold, the flu is generally more intense, makes you feel worse and often shows up suddenly.
If you experience nausea or diarrhea, you probably don't have the flu but have picked up a stomach virus — the "stomach flu" can make you miserable but isn't technically influenza.
The flu can be confirmed by a nasal swab at a doctor's office, according to the CDC. And if you have flu-like symptoms after getting the flu shot, it's not the flu (that's a myth). You can (and should!) workout after getting the flu shot.
When to See a Doctor
If you have a fever, cough, sore throat, runny or stuffy nose, body aches, headache, chills and/or fatigue, it might be time to see the doctor. You may or may not have the flu, and a doctor will diagnose you accordingly.
It's important to know if you have the flu or another contagious virus to ensure you limit your ability to spread it to others (aka, to know if you need to avoid the gym), but generally, most people can recover from the flu without medical help.
However, if you're over 65, are pregnant or have other complications, including severe symptoms, UCSF Health advises that you seek medical help,
Exercise and the Flu
While it's true that exercise boosts immunity, once you're already sick, it's not going to help. And the idea that working out can help you "sweat out" an illness is a myth, according to NYU Langone Health.
You've likely heard that as long as your symptoms are "above the neck" (sneezing, runny nose, light cough), it's OK to exercise, and that's true — with a caveat. "We would generally say take it down a notch," Dr. Montero of the Mayo Clinic says.
Below-the-neck symptoms (a hacking cough, body aches, feeling dizzy and fever) are signals from your body that it needs to focus on healing and it's time to skip the workout.
If You Have a Fever
You should definitely not exercise if you have a fever, which is a common symptom of the flu, advises the Mayo Clinic. Your heart rate becomes elevated with a fever, and exercise can put too much strain on your heart. In some cases it can lead to heart failure.
You also have a higher risk of becoming dehydrated when you have a fever, and exercising exacerbates that risk. Fever indicates that your body is working hard to overcome the flu virus, and the best thing you can do is rest and let your body heal.
Don't Go to the Gym
Even if your symptoms are mild and you don't have a fever, if you suspect you have the flu or have been diagnosed with the flu, don't work out with others.
The flu is a highly contagious illness that is passed directly between people or by touching a contaminated surface, so stay home when you are sick to avoid spreading your germs to other people. A flu sometimes presents with a cough, so don't think about exercising with a cough for the first 48 hours.
You can leave flu germs on workout equipment that other people can pick up if the equipment is not wiped down and sanitized, even six or seven days after getting the flu.
Stick to Moderately Intense Exercise
You can exercise if you have a cold, according to Harvard Health Publishing, although you may want to cut your workout in half. If you have the flu, you shouldn't exercise with the same intensity as when you are well. And if you have a fever, wait until it is gone before you hit the gym.
If your symptoms are mild, stick to gentle to moderate exercises if you just can't give up a workout. Consider going for a low-intensity walk or doing a restorative yoga session.
After You've Recovered
When you are over the flu, return to a regular exercise routine gradually to give your immune system a chance to build back up. If you had a fever, you should wait a couple of days after it breaks before doing any exercise, according to NYU Langone.
And per Harvard Health Publishing, you want your first workout to be so low intensity that you don't get out of breath.
Don't expect to be able to do your old exercise routine right away — it might take a couple of weeks to get back into the swing of things.
To avoid catching the flu, think about working out during less popular hours at your gym during flu season and wipe equipment before using (and definitely after), recommends the University of California Irvine.
But don't skip working out, especially during flu season. There is a general consensus that regular bouts of up to 45 minutes of moderate intensity exercise is beneficial for immune defense, according to a 2020 article in Exercise Immunology Review.
Does working out make the flu worse?
If you have intense symptoms, in particular a fever, working out will make it harder for your body to recover from the flu. Per NYU Langone, exercising with a fever can be dangerous, as it increases your heart rate and body temperature and can increase the risk of dehydration.
Is it bad to workout when you have a cold or flu?
Mild colds with above-the-neck symptoms are fine to exercise during. The flu, however, is usually more intense and warrants taking a break from workouts. If your flu symptoms are truly mild, you can exercise, but stick to low-intensity workouts.
What is the best exercise for the flu?
Rest is the best thing you can do for your body when you have the flu. As you recover, don't do any exercise that gets you out of breath — stick with walks.