Is It a Cold, or Is It Flu? When Are You Too Sick to Work Out?

Should you tuck yourself into bed with a book and a cup of tea when you're sick, rather than head out to the gym? Most people think the answer is obvious — but it may not be.

Are You Sniffling or Sneezing? Working Out May Help You Get Over an Infection Faster

Every winter millions of people who are serious about their health use sniffles, sneezes, coughs, and fever as an excuse to skip their workouts. But a study published by the American College of Sports Medicine reports that moderate exercise may help you get over an upper respiratory infection faster.

 

People who exercise regularly tend to catch fewer colds and to have fewer bouts of flu, although it's certainly a good idea to wash your hands carefully and often when you share a gym with others. Most of the time when you catch the flu, it's because you have breathed in air in which an infected person has recently coughed or sneezed. Touching infected mucus with your hands and then touching your mouth, nose, eyes, or face is the other main way of catching the flu. In the post-COVID age, we're all familiar with all of this, and we're more careful to avoid potential contaminants than ever before.

Even when the virus has entered your body, you won't necessarily get sick. There is a certain minimum number of viruses that have to be absorbed into the lining of your nose or throat to cause infection. How many viruses you need to come down with a cold or flu depends on the strength of your immune system. Smoking weakens your immune system. A single, large dose of vitamin C at the first sign of symptoms activates your immune system. And the effects of exercise depend on when you contract the virus.

• If you do regular, moderate intensity exercise, your exercise habit helps your immune system fight off a cold when you are at rest.
• If you have just done extremely hard exercise or competed in a sports event, then for several hours while you are recovering you are more susceptible to catching colds or flu.

That second characteristic of exercise explains why it is especially important to avoid picking up a cold in a locker room or gym. It is also the reason many professional athletes use herbal adaptogens, such as  eleuthero (once known as Siberian ginseng) or rhodiola, to keep their immune system primed to fight infection all the time. But what if you are already sick?

Exercise a Cold, Rest a Fever

You have probably heard the old adage, "Feed a cold, starve a fever." There is something to the advice. When you eat, your body has to burn the calories. The burning of food creates carbon dioxide, and you breathe more deeply to take in oxygen in and breathe the carbon dioxide out. Deeper breathing loosens up phlegm and helps you get over a cold faster.

Eating a few extra fats and sugars increases your body's production of inflammatory chemicals. That is usually not a good thing. You don't want inflammation in your joints or in your arteries. But when you have a viral infection of the respiratory tract, inflammation can help your body get rid of infected cells and to create the mucus and phlegm that isolate viruses so you can expectorate the infection out of your system.

One time it is important not to feed your cold is when you are taking high-dose vitamin C. That is because eating more increases the acidity of the mucus lining your upper respiratory tract, and vitamin C works best in an alkaline environment. But it's only the first dose of vitamin C that helps you get over your symptoms.

While feeding a cold helps you open up, stoking your calorie-burning metabolic furnace is not a good idea when you have a fever. Your body turns up its thermostat to kill viruses. Adding heat to your fever doesn't make the viruses any more dead. It just makes you more uncomfortable.

The same thing can be said for moderate exercise, which also gets you sweaty and warmer. Anything that makes you breathe a little faster and a little more deeply helps loosen phlegm. Anything that makes you hot and sweaty puts more stress on your immune system and can cause a setback. But there is a simple, commonsense rule that can help you know whether exercise would be beneficial or not.

The "Neck Rule" for Colds and Flu

One good way to know whether exercise will help with your colds and flu symptoms or harm you is the "neck rule." If your symptoms are primarily above the neck, that is, if you are mostly sneezing and perhaps have a little bit of a runny nose, then moderate exercise is highly likely to help you feel better. If your symptoms are primarily below the neck, if you are mostly coughing, then it may be a good idea to skip your workout.

Even when your symptoms are mostly nasal, it's not a good idea to put out a "110 per cent effort" at the gym or on the playing field. Start your workout by doing very light exercise, maybe 50 per cent of the effort you ordinarily give your exercise routine. Then step up the pace over the next 5 to 10 minutes to see how you feel. If exercise makes you feel better, then work out at your normal pace. If exercise makes you feel worse, then do only a light workout. Even Olympic medalists need an occasional day or week off.

It is also important to stay hydrated. Antihistamines, cough syrups, and nose sprays "dry you out." Losing even more fluid through sweating while you exercise can leave you dehydrated. You always need water after your workout to help your muscles absorb the replacement amino acids and sugars they need to bulk out. You need even more water when you have a cold or you are getting over the flu, or your muscles won't benefit, so remember to keep drinking water.

Is is ever a good idea to exercise when you have a full-blown case of the flu? While you have swollen glands, body aches, and fever, get bed rest. And don't do a hard workout for at least two to four weeks after you recover.

And when you do exercise, be sure not to share your germs. It's especially important to wash your hands before you use a treadmill, gym mat, or barbells to avoid giving your infection to others, and to wash your hands after you use a treadmill, gym mat, or barbells, to avoid catching a new infection from someone else. Even better, stay away from the gym and take a walk outside, do a little aerobics routine at home, or run on your home treadmill.