To exercise, or not to exercise? Many of us may ask that question.

If you are feeling under the weather, should you still head on out or will a good rest be the most effective remedy?

A quick self-assessment could give you the answer. 

Are the symptoms:

  • Throat up? 


  • Throat down?
  1. Throat up - Is more than likely a cold, sore throat or blocked nose for example and exercise is fine to carry on undertaking. 
  2. Throat down - May indicate an infection or something more serious that could be made worse by exercise.

Dr Hopcroft (General Practitioner within the NHS), suggests "If your symptoms are not severe and you generally feel OK, then you can exercise. 

“If you feel absolutely rotten, it is probably best not to exercise."(1) Exercising with a fever can make you feel worse. 

“In very rare cases, exercising with a fever (38° C or above ) can lead to the virus affecting your heart, which can be dangerous." (1)

Research suggests that moderate exercise improves the immune system and the response to viral infections. It can restore the body’s optimal antibody responses (2,3,4).

However, we must be mindful of undertaking more intense and prolonged intense exercise bouts, as this can spread the infection and become dangerous (3). An acute bout of intense exercise can suppress the body’s antibody production (4).

Amongst other types of infections, viral infections are the most common cause of a heart condition known as ‘Myocarditis’. Myocarditis is an inflammation of the wall of the heart and may lead to more severe conditions. Myocarditis during the flu will typically go undetected, however, the presence of vigorous exercise has the potential to cause a life-threatening condition (3,8).

Symptoms Can Include:

  1. Heart palpitations
  2. Chest pain
  3. Swelling in the hands, legs, ankles and feet

Myocarditis can affect the function of the heart and the normal electrical signals leading to complications such as; permanent damage to the heart, heart attack, stroke and arrhythmia's (7). 

Heart Inflammation

When we feel unwell, the body requires recovery. Any strenuous exercise undertaken while we feel ill is not likely going to result in any significant progress. As we simply do not have the same work capacity or energy levels. We could actually be delaying the recovery process and potentially cause us further harm.

Dr Ursula Hildebrandt, a Sports Cardiologist, states the best protection is to recover thoroughly from any illness before we exercise.

"A general rule of thumb is to wait at least two days after a bout of fever, and you have stopped presenting green or yellow phlegm,". Phlegm indicates that dangerous germs are still moving around the body (5,6).

To summarise, exercise will improve your immunity. But sometimes we may just need that extra time resting before restarting our regime. If you are unsure about the severity of your illness always seek medical advice from your doctor.


  1. https://www.nhs.uk/live-well/exercise/safe-winter-exercise/
  2. Martin SA, Pence BD, Woods JA. Exercise and respiratory tract viral infections. Exerc Sport Sci Rev. 2009;37(4):157–164. doi:10.1097/JES.0b013e3181b7b57b
  3. Shinkai S, Shore S, Shek PN and Shephard RJ. Acute exercise and immune function. Relationship between lymphocyte activity and changes in subset counts. Int J Sports Med 13: 452-461, 1992.
  5. https://www.welt.de/sport/fitness/article148069022/Sport-mit-Erkaeltung-ist-lebensgefaehrlich.html
  6. https://www.dw.com/en/when-sports-are-bad-and-threaten-the-heart/a-16309687
  7. https://www.cardiomyopathy.org/about-cardiomyopathy/myocarditis-and-cardiomyopathy
  8. Cardiovascular manifestations associated with influenza virus infection; https://doi.org/10.1016/j.ijcard.2008.04.044