If You Run With a Cold, You'll Only Make Yourself Sicker
"Always use common sense and listen to your body," says Kayser. "If you think running might make you feel better, it is safe and may even clear up a runny nose. But always use the 'neck check'--if your symptoms are below your neck (chest cough, muscle aches), it's better to rest." Symptoms below the neck may indicate a more serious illness like influenza or pneumonia, for which you'll need to seek medical attention.
A fever is another indication that you may need to take some time off. "Anytime you have a fever above 100.4 degrees F (a general guideline), it's wise to seek medical attention and avoid activity," Mohseni cautions. Because running raises your core temperature, running with a fever puts you at risk for hyperthermia, or overheating, he explains. The most serious consequence of this condition is heat stroke, which in extreme cases can lead to kidney failure.
If indeed you're dealing only with a pesky cold and decide to lace up for a run, feel free to shrug off suggestions that you'll make yourself sicker. Running with an upper respiratory tract infection--the medical term for a common cold--has not been shown to delay recovery time.
In a study published in the Journal of Medicine & Science in Sports & Exercise, researchers at Ball State University deliberately infected volunteers with rhinovirus, the culprit of at least one third of adult colds. One group exercised on treadmills for 40 minutes every other day at moderate levels, while the control group rested. At the conclusion of the study, scientists found no difference between the group members' severity of symptoms or the time it took to recover.
Remember, however, that even if you're feeling better, but not 100 percent, it's still not the right time to tackle tough interval runs. "Any time you've been sick, you should resume your training at a lower level of intensity for a few days," Kayser says. "Run at a slower pace for less time or take a few days to cross- train," Mohseni suggests. If you're recovering from severe symptoms, rest for at least two weeks, and always consult with your doctor.
To make sure you're not overdoing it when you return to your regular runs, Mohseni recommends checking objective data that can indicate whether your body's still recovering: Make sure your resting heart rate is not elevated; record how you feel after exercise by keeping a training log, assigning a number to rate fatigue from 0 to 10; and examine your sleep cycles--abnormal patterns may indicate physical distress.
Running in the Cold Will Make You Sick
Simply being cold will not make you sick--this is nothing more than an old wives' tale. "You are not likely to get sick if you dress warmly and remove the wet clothes promptly after your run," Kayser says.
The source of this common misconception probably comes from the fact that many viruses are more easily transmitted during cold weather. Cold weather, which is usually accompanied by drier air, does create optimal conditions for catching colds.
"Our mucous membranes break down in drier weather," Mohseni says, and germs are then transmitted, most likely via hand to nose or hand to mouth.
That's not to say that there aren't risks to slogging it out in a cold rain. "You should not wear cold, wet clothes for a prolonged period of time after a run. This will increase your chances of getting a bacterial infection," says Kayser. Perhaps the biggest risk of running in the rain is an accidental fall. So, be sure your shoes provide excellent traction, and watch your step.