Heart Health

Updated 27 September 2016

To train or not to train?

Exercise is supposed to be good for us. But when is it time to take a rest?


Exercise is frequently described as the “best medicine available”. Because of this, many experts wish they could put it into pill form, bottle it and make a fortune! But as powerful and far-reaching as the benefits of exercise are, there are times when it is healthier to rest – for example, when one is hit by a respiratory tract infection.

The first important step in determining whether or not you can exercise when you’re not feeling 100 percent, is to distinguish clearly between the cold and the flu virus.

Most colds are caused by rhinoviruses that cause a runny nose, sneezing, coughing, a sore throat and moderate gland swelling. The duration of a cold is usually about one week and any symptom lasting longer than two weeks should be medically assessed to ensure it hasn’t become a secondary bacterial infection such as sinusitis or bronchitis. Alternatively, it could be an allergy, in which case you might need to undergo some tests to see what is causing the irritation.

Flu – short for "influenza" – is a more serious viral infection. Whilst some of the symptoms of flu include those experienced with a cold, it also has some serious systemic effects which include: severe muscle, bone and joint aching, persistent headaches and significant fatigue. Glands are often swollen much more noticeably with flu. Flu also has the potential to proceed to more serious conditions such as a chest infection or bronchitis.

Follow these guidelines for exercise when affected by a cold or flu virus. However, if there is any doubt about your safety, rather consult a physician:

If the symptoms are mild and above the neck only, such as nasal congestion, a runny nose and a mild sore throat, then you can do a trial exercise session of about 10 minutes at a low intensity. If you feel fine after your 10 minutes trial, then you can continue with a longer session. However, if you feel lethargic and weak, then rather rest for a day or two more before trying again.

If, on the other hand, your symptoms are below the neck, such as chest congestion, a phlegmy cough, aching bones or muscles, fever, shivering or chills, or a raw throat, then exercise must definitely be avoided.

In this case, the safest approach is to avoid all exercise until the symptoms are completely gone. At that point, a slow return to a normal exercise routine should be followed; but even then, proceed with caution.

Never attempt to "sweat out" a feverish illness with intense exercise – this quite simply doesn't work and in fact can lead to a severely debilitating condition known as post-viral fatigue syndrome. Symptoms of this include weakness, increased fatigue, frequent infections and depression and it can persist for months or even years.

Exercising with flu also puts one at risk of suffering from viral myocarditis* – where the flu virus invades the heart muscle and causes significant and irreversible damage.

Hopefully, your healthy lifestyle precludes you from suffering from any respiratory tract infections this winter, but if you do succumb, make sensible choices and get well quickly.

Tips for training

  • Engage in a moderate, consistent exercise programme. Research has shown that this is definitely an immune booster.
  • If you train regularly and for long periods, consume carbohydrate beverages before, during and in the two-hour period after training to maintain blood sugar levels and minimise stress hormones. This will result in improved immune function.
  • Avoid overtraining. Rest if you are feeling below par.
  • Consider having a flu injection if you plan to train through the winter months.

*Myocarditis – an inflammation of the myocardium, the middle layer of the heart wall – is the main concern if you exercise while you have flu. This uncommon condition can cause a variety of signs and symptoms, including chest pain and abnormal heart rhythms. If myocarditis becomes severe, the pumping action of your heart weakens, and your heart won’t be able to supply the rest of your body with enough blood. Clots could also form in your heart, leading to a stroke or heart attack.

[This is an edit of an article by Kathleen Mc Quaide and Mandy Collins that originally appeared in Heart magazine, Winter 2008. The current edition of Heart is on sale now.]

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