I awoke to three inches of snow Sunday morning, and the beginning of a head cold. By the end of the day I had lost my voice, couldn’t breathe through my nose, and felt like someone rubbed sandpaper along my tonsils.

I still went for a run.

And I still put in an hour and a half on my bike.

It’s a sickness of a different variety.

Cold temperatures bring an increase of illness around the world. Running while ill can be helpful or hurtful depending on the symptoms and the intensity of your runs.

Congestion, cough, runny nose, sore throat, headache, fever, diarrhea, and vomiting.

Obviously running with some of these symptoms would be unpleasant to say the least, not only for you but for others around you. Running with a fever is dangerous because the fever already increases your body temperature, and running will increase it even more.

What about the other symptoms? Running can help relieve congestion, which can then help with the related cough and sore throat. Running (exercise in general) can decrease the length of illness and prevent it. Runners, on average, take in more fluids than people who don’t exercise or run. The increase in fluids flushes your system of toxins through increased urination and sweat.

Exercising also sends antibodies and white blood cells through the body more quickly allowing you to detect illness sooner and to fight it off more effectively. The increase in body temperature caused by running or exercising, so long as you don’t have a fever, slows the growth of bacteria.

Physical and emotional stress causes the body to release stress hormones. These hormones reduce the effectiveness of the immune system. Avoid intense workouts, such as speed training or hill climbs while ill. These types of workouts place stress on the body and can lengthen the duration of illness or make symptoms more severe.

Regular running or other types of aerobic exercise will improve your immune system functioning boosting your body’s ability to prevent and fights illness.