While it may be tempting to make up for lost time, don’t run yourself ragged after an illness. While exercise can boost your immune system, it’s best to ease back into your running routine after being sick. Your endurance may be impaired after illness, so don’t be surprised if you can’t run as hard or as long as before. Take extra time to prepare your body for physical activity after being sick. By taking a slow and steady approach, you can safely build up your strength and endurance and return to your normal running routine with less risk of a setback.
Impact on Immunity
Moderate physical activity can have a positive impact on your immune system, temporarily boosting the production and efficient movement of cells that help fight bacteria and viruses. While moderate exercise can boost your immune system, extreme exercise sessions of 90-plus minutes can decrease your immunity for up to 72 hours, leaving you at risk for another illness. Running too hard or for too long when recovering from an illness can decrease your white blood cell count and increase stress hormone production, which can suppress your immune system.
When to Begin Running
You don’t necessarily have to wait until all of your symptoms subside to return to running. The American Council on Exercise refers to the the “above the neck” rule to determine if it is safe to exercise. (See Reference 1) If you are suffering from a head cold with symptoms above your neck (runny or stuffy nose, cough) then moderate exercise is usually safe. (See Reference 1) But if you have symptoms below the neck, like respiratory symptoms associated with the flu, or diarrhea and vomiting experienced with intestinal illnesses, you should not run until your symptoms resolve. (See Reference 2)
Building Up Endurance
It can take up to five days after an illness to be in running shape. If your illness has prevented you from running for up to five days, ease back into your running routine at approximately 80 to 90 percent of your normal distance at a casual pace. If you are able to perform two to three easy runs successfully, then you can ramp back up to your normal running regimen. If your illness prevented you from running for six to ten days, begin at 60 to 70 percent of your normal distance for the first few days. For longer illnesses, it may take up to two weeks of modified workouts to return to your regular running routine.
Take Extra Precautions
Illnesses can cause dehydration, so when you return to your running regimen, be vigilant about hydrating before and during your run. Drink two cups of water right before your run and approximately one cup of water every fifteen minutes during your workout. After your run, replenish fluids with two additional cups of water. Be equally vigilant in keeping track of your exertion level. With your body in a weakened state, you are more vulnerable to overexertion. This is especially true if you run outdoors in an extremely hot or cold climate. If possible, use an indoor track as you return to your running routine. Take extra breaks as needed and don’t hesitate to end your run early if you experience any symptoms of overexertion like dizziness, nausea and fatigue.
- American Council on Exercise: Can Exercise Reduce Your Risk of Catching a Cold?
- MarathonGuide.com: "To Run or Not to Run... What to Do When You're Sick"
- RunnersConnect: How to Return to Running After Injury, Sickness or Missing Training
- Massachusetts Department of Public Health: Getting Enough to Drink: Dehydration and the Flu
- UC Riverside: Guidelines for Exercise