Moderate intensity exercise improves immune function and several research studies have demonstrated a reduction in both severity and frequency of viral infections in those participating. Exercise  changes the immune system , increasing the benefits over time with repeated sessions. Intense  exercise however, before or during a generalized viral infection ( whole body), particularly with a fever, is associated with more severe and prolonged symptoms.

The general ' rule' used by the Australian Institute of Sport is known as the ' neck' rule.  If the symptoms are mild and from the neck up ( sore throat or runny nose) moderate exercise may be beneficial.

Aerobic exercise ( for example fast walking) can be beneficial at the start of a cold, opening the airways, improving mucus flow and releasing natural endorphins.

Training with a fever, joint or muscle aches or bronchitis is not recommended as is training with a resting heart rate 10% above your normal resting rate. The same systems activated to fight off significant illness also repairs and builds muscle damage that occurs with high intensity training.

Advice for whole body illness includes rest and a medical review of the symptoms don't settle after several days.

Fitness is not affected by missing a few days of exercise  and training with an illness will not be quality training.

Once the symptoms have settled, it is advised to return to to pre- illness schedule gradually, with light exercise the first day, then over 2-3 days following a mild illness and 2-3 days light exercise and a slower return to full training if a week was missed.

Exercising at intensity or for long periods of time, can result in a temporary reduction in immune function, for example the risk of a upper respiratory tract infection in athletes, increased  2-6 times over a two week period after a marathon race, compared to those training who did not race.

Susceptibility to infection also increases for many athletes when reducing their training intensity immediately before an event ( tapering). This is thought to be an immune response related to the reduced stress the body is under as the training load is reduced.

The immune system of marathon runners has also been demonstrated to undergo a steep decline in the 6-9 hours after running for 2-3 hours.

Suggestions for reducing the risk of infection include:


  • No smoking
  • Eating a balanced diet, and replacing carbohydrates and protein rapidly after a training session
  • Managing stress
  • Adequate sleep
  • Practicing good hygiene, washing hands, not touching face and mouth, avoiding sick people
  • Balancing workouts with rest and recovery
  • Continue training during the tapering period, maintaining high intensity levels over smaller distances
  • There is no evidence currently regarding the value of any supplements in preventing illness under these circumstances ( for example, zinc, vitamin C , anti-oxidants and echinacea, ) the evidence lying more with the benefits of whole food containing these substances rather than individual capsules.









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