Should you run when you are sick?

Sports medicine doctors often use a simple rule. If your symptoms are above the neck, a light run or walk is probably fine. If they are below the neck, or spread across your body, rest. A sports medicine physician quoted by Cleveland Clinic puts it this way: with a runny nose or congestion, it is probably safe to exercise.

The rule has limits. If you have asthma or a heart condition, Cleveland Clinic’s advice is to rest when you are ill rather than test it. And how you feel counts. A cold that leaves you wiped out is a reason to stay in bed, even if it is all above the neck.

Illnesses also change. Some start with a scratchy throat or a stuffy nose and turn into fever and aches a day later. Check in with yourself each morning, and use the next-day test: if you feel worse the day after an easy run, rest until you feel better.

A fever means your body is fighting an infection. Cleveland Clinic warns that exercising with a fever can lead to dehydration and make it harder for your body to control its temperature. Your heart is also working harder at rest. A run on top of that adds stress and no fitness worth having.

Wait until the fever has gone without fever-reducing medicine before you run again. Pills can mask a fever and make you feel better than you are.

While you rest, drink regularly and eat what you can. A fever, vomiting or diarrhea all cost you fluid and salt. Water, broth and an oral rehydration or electrolyte drink help you catch up, see electrolytes for running. Plenty of sleep matters more than any workout that week.

• Cut your usual effort and time by at least half, as Cleveland Clinic suggests. A 40-minute run becomes 20 minutes, very easy.
• Walk instead of run if even easy jogging feels hard.
• Skip intervals, hills and long runs until you are well.
• Run alone or on a treadmill at home. Coughing and sneezing at a group run passes the cold around.
• Drink more than usual. A blocked nose and mouth breathing dry you out.

Stop at once and rest if you get chest pain, have trouble breathing, feel dizzy, or feel faint. Those are not signs to push through. Call 911 for chest pain that does not go away or severe breathing trouble.

Cleveland Clinic also suggests swapping to lighter activity while you are under the weather: walking instead of running, or gentle, low-impact movement like yoga. These keep the habit going without asking much of your body.

• A 15 to 20 minute walk outside in daylight.
• Easy stretching or yoga at home.
• A slow spin on a stationary bike.
• Nothing at all, if you feel poorly. Sleep and fluids do more for you.

Cleveland Clinic’s doctor notes that even after a couple of days off, you bounce back fairly quickly. A few missed runs cost you very little fitness. After a fever or a chest infection, check with a doctor before hard efforts.

An example: you usually run 3 miles four times a week, and a flu keeps you in bed for five days. Once the fever has gone, walk for 20 minutes. Two days later, try 1.5 miles of easy running with walk breaks. Over the next week, go to 2 miles, then back to 3 if each run leaves you feeling fine the next morning.

Watch for signs that you came back too soon:

• Your heart rate is much higher than usual for an easy pace.
• You feel more tired after an easy run than before it.
• A cough that was settling comes back or gets worse.
• The fever returns.
• You need a nap after every run for days.

If any of these happen, drop back a stage and give it a few more days. If they last, see a doctor.

Do not push through illness to beat a window. If you have not tapped Start yet, wait until you are well, since the window only begins then. The long challenges leave room for sick days: TURTLE is 42.3 miles (68 km) over 39 days, about 1.1 miles a day on average. Lose four days and the daily average barely moves. Easy walks count toward the total too, see walking challenges with medals.

On a short challenge like LOKI, 7 days, a cold early on is a good reason to wait before you start. Sleep is the other half of getting better, see rest days and sleep for runners.

• Running a planned long run on the first day of a cold because it is on the schedule.
• Taking fever-reducing pills so you feel well enough to run.
• Jumping straight back to your old pace and distance after a week in bed.
• Joining a group run while still coughing and sneezing.
• Skipping fluids because you do not feel thirsty while ill.

• Can running sweat out a cold? No. A light run may make you feel clearer for a while, but it does not shorten a cold.
• Can I run with a sore throat? A mild one, gently, if the rest of you feels fine. Rest if it comes with fever or aches.
• How long after the flu can I run? Wait until the fever is gone and you feel well, then start with short walks. Flu often leaves you tired for a week or more.
• Should I run with allergies? Allergies are not an infection, so many people run as normal. Check pollen counts and run when they are lower.

This is general information for healthy adults, not medical advice. If you have a health condition, are pregnant, or have not exercised in a long time, check with a doctor before you start.

• Cleveland Clinic, Should You Work Out When You’re Sick?