Should You Continue to Exercise or Rest When You are Sick?


This is a very common question many athletes are faced with during periods when they become ill. Most are unsure if they should work through the pain to continue their training, or if they should take some, potentially valuable, time off. Part of this doubt may be that physically active people do not seem to become ill as often as sedentary individuals. In fact, between 60-90% of physically active people report that they feel they do not get sick as often as sedentary people they are around. And their feelings are substantiated; as research has demonstrated that regular, moderate exercise does have several positive effects on the body’s immune system.


Positive effects of regular, MODERATE exercise

There are several positive changes that occur within the immune system during moderate physical activity. These effects during exercise are transient, and return to near baseline levels after the exercise session. However, each exercise session provides a boost to the immune system and increases its surveillance and protection of the body. In the long term this may translate to a reduced risk of infection and fewer days of sickness.

There are mechanisms that occur at the cellular level in response to exercise to improve the immune system. Moderate exercise causes there to be a decrease in various ‘stress hormones’ and the release of pro-inflammatory chemicals, both of which can cause a suppression of the immune system. A session of exercise can cause there to be a leukocytosis, or an increase in the number of white blood cells into the bloodstream. The leukocytes (white blood cells) also change their location in the body in order to provide better surveillance for infection. These changes are brought about by a release of chemical substances that are triggered by the activation of various nervous system pathways. It is these alterations during a single bout of moderate exercise that are “immuno-enhancing.”


What about in SICKNESS

Although there may be a benefit to regular, moderate intensity exercise, what happens when an athlete becomes sick? It is difficult to provide definitive answers in human studies, as this is difficult to measure. But animal studies have shown that if an animal is exposed to a virus and then undergoes exhaustive exercise, they more frequently manifest infection and tend to have more severe symptoms. It has also been well documented that athletes’ performance is reduced during a period of illness, possibly reflecting that it is more difficult to physically perform while sick.

Even though a moderate exercise session does provide a net benefit, it has been demonstrated that there is a depression of immune function approximately 3-24 hours after exercise, especially high-intensity sessions. Studies have found that there is a transient decrease in the function of the leukocytes in the body and their ability to kill viruses and bacteria. It is important to note that it has been proven that there is a direct suppression of leukocyte function and this change is not secondary to inflammatory changes that occur after a workout.

From this it can be extrapolated that pushing the body to its limit during a period of illness can result in a greater decline in the function of the immune system to fight off the current infection. These negative effects of the immune function may not only hinder the body’s ability to ward off infection, but may also result in a prolonged period of decreased athletic performance.


Recommendations While Sick

Clinical authorities of exercise immunology recommend the following:

  1. “If one has common cold symptoms (runny nose and sore throat without fever or general body aches), intensive training may be resumed a few days after the resolution of symptoms”
  2. Mild to moderate exercise (walking) when sick with the common cold does not appear to be harmful.”
  3. With symptoms of fever, extreme tiredness, muscle aches, and swollen lymph glands, 2 to 4 weeks should probably be allowed before resumption of intensive training.”

Keep It Simple: The Neck Rule

The above advice may be more difficult to remember, or not make sense to you. Therefore, a general way to think about exercise while sick is to think of the Neck Rule. This adage relates that if the symptoms of your sickness are Above your Neck then some mild exercise is acceptable. If your symptoms are Below your Neck (have congestion in your chest, generalized body aches) and/or a fever is present, then a period of rest with gradual progression to training is recommended.


Chase King, MS-IV

David Carfagno, D.O., C.A.Q.S.M.



Diment, Bethany C., Matthew B. Fortes, Jason P. Edwards, Helen G. Hanstock, Mark D. Ward, Huw M. Dunstall, Peter S. Friedmann, and Neil P. Walsh. "Exercise Intensity and Duration Effects on In Vivo Immunity." Medicine & Science in Sports & Exercise 47.7 (2015): 1390-398. Web.

Gleeson, M. "Immune Function in Sport and Exercise." Journal of Applied Physiology 103 (2007): 693-99. Web.

Mackinnon, Laurel T. "Chronic Exercise Training Effects on Immune Function." Medicine & Science in Sports & Exercise 32.Supplement (2000): n. pag. Web.

Nieman, David C. "Current Perspective on Exercise Immunology." Current Sports Medicine Reports 2.5 (2003): 239-42. Web.

Nieman, David C. "Exercise, Upper Respiratory Tract Infection, and the Immune System." Medicine & Science in Sports & Exercise 26.2 (1994): 128-39. Web.

Simpson, Richard J., Hawley Kunz, Nadia Agha, and Rachel Graff. "Exercise and the Regulation of Immune Functions." Progress in Molecular Biology and Translational Science Molecular and Cellular Regulation of Adaptation to Exercise (2015): 355-80. Web.


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