Colds and flu

Updated 27 September 2017

Should you exercise when you have a cold or flu?

Studies indicate that if you exercise regularly, as opposed to leading a sedentary lifestyle, you will be less prone to illness.

In winter we spend more time indoors which means we are in closer contact with other people who may be carrying germs.

Moderate exercise

But flu is not something to be sneezed at, and worldwide up to five million people get seriously ill during the "flu season", and around a quarter of a million die from it, so it makes sense to take the necessary precautions to stay well this season. 

You may not be able to banish those "lurgies" completely but research shows that moderate levels of regular exercise are thought to help strengthen the immune system. Studies indicate that if you exercise regularly, as opposed to leading a sedentary lifestyle, you might not become immune, but definitely less prone to illness. "This does not mean you should exercise when you have flu though," warns Bonitas Medical Fund. 

Read: The three types of flu viruses

Be warned, though, that this doesn’t mean the harder you exercise the better off you are! In fact, a really hard workout, or overdoing it, can knock your immune system.

Ever had inexplicable sniffles or a sore throat the day after what you would consider a "good workout"? 
These are symptoms of what’s medically known as an upper respiratory tract illness or infection (URTI). This is more likely to happen after continuous, prolonged (more than 1.5 hours) of moderate to high-intensity exercise. This is even more prevalent if you are not eating the correct foods.

Flu injection recommended

So, with moderate exercise and good nutrition your body should be able to fight off the bugs on its own. When you consider that we experience about 2-4 common cold episodes a year and sore throats are the most common reason for athletes visiting the doctor, it makes sense to look after yourself in winter – not only to keep away colds and sore throats but to prevent them becoming bad enough to need antibiotics.

The main cause of respiratory infections is viruses such as rhinovirus and adenovirus that result in symptoms of the common cold and flu. Bonitas recommends that those who have poor immune systems or are over the age of 65 should have a flu injection before the start of winter, although you can be inoculated right up until the end of August.

Read: Counting the cost of having the flu in SA

If you are unlucky enough to catch one of these "lurgies", there are some basic guidelines for safe exercise during your illness and recovery.

Bonitas recommends some basic guidelines for exercise during infectious episodes. It is a good idea, though, to consult your doctor before you begin exercising:

  • DAY 1 of illness: Do not exercise strenuously when experiencing URTI symptoms like a sore throat, coughing, runny or congested nose. Avoid ALL exercise when experiencing symptoms like muscle/joint pain and headache, fever and generalised feeling of malaise, diarrhoea or vomiting.
  • DAY 2: Avoid exercise if fever, diarrhoea or vomiting present, or if coughing increases. If no fever is present and there is no worsening of "above the collar" symptoms, undertake light exercise (heart rate < 120 beats per minute) for 30-45 minutes (indoors during winter) by yourself.
  • DAY 3: If fever and URTI (or gastrointestinal) symptoms are still present, consult your doctor. If no fever is present and there is no worsening of initial symptoms, undertake moderate exercise (heart rate < 150 beats per minute) for 45-60 minutes, preferably indoors and by yourself.
  • DAY 4: If there is no symptom relief, do not try to exercise, and go and see your doctor. If this is the first day of improved condition, wait one day without fever and with improvement of URTI or gastrointestinal symptoms before returning to exercise.

Read: How do people get flu?

However, it is important to stop training and consult your doctor if a new episode with fever occurs or if initial symptoms become worse, coughing persists or breathing problems during exercise occur.

It is generally agreed that prevention is always preferable to treatment, and here are some practical guidelines to keeping healthy during winter:

  • Advise sick co-workers to stay at home if symptoms are likely to be infectious – or avoid them if they do come in.
  • Wash hands before meals and after direct contact with potentially contagious people, animals, blood, secretions, public places and bathrooms.
  • Use disposable paper towels and limit hand to mouth/nose contact when suffering from respiratory or gastrointestinal infection symptoms. Carry alcohol-based hand-washing gel with you.
  • Do not share drinking bottles, cups, towels etc. with other people. Ensure adequate dietary energy, protein and essential micronutrient intake and avoid crash dieting and rapid weight loss. It is a good time to take a nutritional supplement, including Vitamin C
  • Ensure adequate carbohydrate intake before and during strenuous prolonged exercise.
  • Wear appropriate outdoor clothing in inclement weather and avoid getting cold and wet after exercise (have a change of dry clothes).
  • Get adequate sleep (at least 7 hours per night is recommended).
  • Keep other stress factors to a minimum where possible.

Of course it’s best to avoid getting ill at all by maintaining a healthy lifestyle, getting enough exercise and taking reasonable and practical precautions. But if you are ill, remember to look after your body and give yourself time to recover before you immerse yourself in all of life's challenges again!

Read more:

Symptoms of flu

Causes of flu

Preventing flu


Ask the Expert

Flu expert

Dr Heidi van Deventer completed her MBChB (Bachelor of Medicine and Bachelor of Surgery) degree in 2004 at the University of Stellenbosch.
She has additional training in ACLS (Advanced Cardiac Life Support) and PALS (Paediatric Advanced Life Support) as well as biostatistics and epidemiology.

Dr Van Deventer is currently working as a researcher at the Desmond Tutu Tuberculosis Centre at the University of Stellenbosch.

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