Research has shown that regular moderate exercise helps to protect you against colds and sore throats, but intense and prolonged (>1.5 hour) exercise can put you at a higher risk.
Hard training athletes seem to pick up more colds and suffer longer from them than the general population. Studies have shown that there is a 100 to 500% increase in risk of getting a cold following a marathon or an ultra-event, even though most of these are recurrences from prerace infections. Sometimes the symptoms are not caused by infections though, but by inflammation due to drying out of mucosal surfaces, to inhalation of pollutants or to allergies.
Your first line of defence against viruses is the antibodies in your saliva and lining of your nose and sinuses.
If they manage to get through they will bump into your second line: macrophages that will engulf and kill them.
To infect you, viruses have to invade your cells and replicate in them, but your natural killer cells will eliminate the affected cells before this can happen.
In the meanwhile your third line of defence is joining in: B lymphocytes start to produce antibodies and cytotoxic lymphocytes are attracted to the site to help eliminating infected and damaged cells.
The three levels reinforce and complement each other, and the distinction between them is often unclear.
Regular moderate exercise increases the antibodies in your saliva and mucosal surfaces, and therefore helps you to fight off viruses. In contrast, after a bout of prolonged, intensive exercise, all the immune cells decrease in number for 3 to 17 hours.
Does this mean that hard training is bad for you?
A temporarily drop in the number of immune cells does not make you more vulnerable, but if it happens too often or is too deep, it could be just enough to increase your risk of picking up a common infection such as a cold or a sore throat, or reactivate an old one. However, hard training athletes are not more at risk of severe infections than the general population.Exercise has so many other benefits, such as reduced risk of cardiovascular disease, cancer or diabetes, that having occasionally a cold is a small price to pay.
Even so, you do not want to pick up a cold when training for a hard race, or just after a marathon or ultra-event. The best solution would be to follow a well-balanced training plan with enough rest to allow your immune system to recover after each hard bout. But what else can you do?
From tricks that are useless…
In 2004 Christian Fisher and his colleagues showed that taking large quantities of vitamin C and E for 28 days before intense exercise reduced the depression of the immune system. But their data showed that it could also decrease the trainings effect, and therefore limit what you gain from your hard work, and even be bad for your health in the long term.
Glutamine is considered as a “fuel” for white blood cells, but studies have not demonstrated any effect of supplements.
Via some that might help…
Echinacea, elderberry, garlic and ginseng are very popular, but as yet there are not enough scientific studies to prove that they can prevent colds.
Or are very promising…
Probiotics influence the microbiological flora in the gut and interact with the intestinal and immune cells. Studies have demonstrated that they can help people in stressful situations to defend themselves against infections, including colds and sore throats. There is therefore hope that they could also help athletes, but as yet only a few studies have been done. Further research is needed.
…to some that are proven,
Studies have shown that taking 30 to 60 g carbohydrates per hour during exercise reduces the effects on the immune system. This is about the amount you usually take during endurance events to delay fatigue, and as yet there are no reasons to believe that it impairs the training effects or your health. A recovery drink afterwards will help to shorten the time your immune cells are reduced.
Zinc lozenges can prevent colds, and reduce their duration and severity if you start taking them within 24 hours of the first symptoms. Expect a bad taste and some nausea.
but do not forget the obvious ones
Eat a well-balanced diet to keep the vitamins and minerals in your body at an optimum level.
Try to reduce all other risk factors:
Keep psychological stress to minimum.
Avoid rapid weight loss.
Make sure that you have enough sleep.
Do not over train.
Avoid contact with sick people and large crowds.
Avoid touching your eyes and your nose with your hands and wash your hands regularly.
What can a virus do to me?
When you are infected, you break down proteins from your muscles to deliver nutrient to your immune system, and to supply the increased energy needed for fever. Your muscles are therefore wasting away, and you are losing strength. The amount you lose will depend on the severity of the disease.
Studies by Friman demonstrated that young male athletes lose about 15% of their strength after an illness requiring a week of bed rest. As your heart is also a muscle, it will contribute as well. A 25% reduction of aerobic capacity was shown in the same study group, due to the combined effect of bed rest and illness.
The nervous system is usually also affected by fever and infection, and your coordination will be decreased.
When can you start training again after an illness?
Unfortunately nobody really knows. Easy exercise during a light infection does not seem to be dangerous, and as a rule of thumb, if the symptoms are only from the neck up a light training is usually possible.
If you have only a cold without any whole-body involvement such as fever, muscle pains, swollen glands or extreme tiredness, you can resume regular training when the symptoms are over. But if you have suffered from a systemic involvement, it is safer to wait for two to four weeks.
Vigorous exercise during or too soon after an infection could make it more severe and lead to a recurrence, a complication or a myocarditis (inflammation of the heart muscle). A few athletes have died following vigorous exercise during or just after an illness.
Every athlete and every micro-organism is different and you have to use your own common sense to stay safe.
Disclaimer: This article is for general information only and cannot guide diagnosis and/or treatment. If you have any concerns or questions, you should talk to a qualified health provider.