How many times have you looked outside on a cold, rainy, winter’s day and said to yourself if I go out training in this will I get sick?

To answer this question we need to look at how exercise affects the immune system. Exercise represents a physical stress which the body reacts to with a certain pattern of hormonal and immunological responses. Depending on the volume and intensity of the exercise will determine the pattern of the response and whether the immune system is stimulated or suppressed. However, it should not be forgotten that other factors such as nutrition, psychological stress and training status will also influence the immune response to a specific training session.

During a strenuous training session there is an increase in stress hormones such as adrenaline and cortisol. Adrenaline increases during exercise in response to both the intensity and duration of the exercise bout. Cortisol increases only in response to exercise of long duration (greater than 1 hour) and shows persistently high levels for hours after the cessation of exercise (Pedersen & Hoffman-Goetz, 2000). Both of these hormones have a direct effect on immune variables such as cytokines and lymphocytes which play a big part in the body’s defence against infection. Though lymphocytes increase in concentration during exercise, concentrations drop below pre-exercise levels after long duration exercise bouts (Pedersen, Bruunsgaard, Jensen, Krzywkowski, & Ostrowski, 1999). It therefore appears that after strenuous exercise there is an “open window” where the body is vulnerable to infection (Pedersen et al., 1999).

OK, so we have figured out that a long hard ride may increase our susceptibility to infection after training but will training in the cold and wet increase our vulnerability further? The answer is quite possibly, yes. Upper Respiratory Tract Infections (URTIs) such as colds and flu’s show definite seasonal variability. One theory to explain this seasonal fluctuation is that the inhalation of cold air reduces the temperature of the nasal passages which is enough to inhibit nasal respiratory defences (Eccles, 2002).
Exercise in cold weather may very well increase the chances of catching a cold if you are exposed to the virus post-exercise. You need to be exposed to a virus to catch it so if you avoid other people with the cold or flu after training you will be taking a very sensible precaution. Don’t forget that other factors such as stress and nutrition will also influence your immune system’s ability to fight infection and with prudent precautions training outdoors in the winter will not necessary make you ill.

Most athletes that participate in endurance sports or even individual sports in general are highly self motivated. Sometimes this high level of motivation can lead to training or competing when the body is just not up to it as is shown by the common occurrence of staleness, overtraining and illness just before an important event. Sometime backing off and letting the body recover reaps greater rewards than train, train, train. So if you wake up in the morning with a scratchy throat what is the right decision, to train or not to train?

The first step is to diagnose whether you are suffering from influenza or a cold. This is not always as easy as it sounds and a visit to a registered GP is highly recommended if in doubt. Both the cold and the flu are viruses however the flu is a systemic (whole body) infection whereas a cold is an infection of the upper respiratory tract (URTI). Common symptoms of the flu are full body aches, fevers and fatigue whereas a cold is normally limit to chest and nasal congestion. With a full body infection exercise is not recommended as the immune system is already under considerable stress fighting the infection and any additional stressor such as exercise could lead to secondary complication such a lung infections or heart complications.

Colds on the other hand are infections limited to a specific area and though the immune system will be working hard to combat the infection there are some arguments for a moderate, but not strenuous, exercise to help stimulate the immune system.

Strenuous exercise has the potential to suppress the immune system therefore logic says if the immune system is already fighting an infection such as a cold, strenuous exercise isn’t going to help the situation and will likely increase the recovery time. Moderate exercise on the other hand appears to stimulate the immune system. In general epidemiological studies using self reported symptoms of URTI have found reduced URTI symptoms after moderate exercise and an increase in URTI symptoms after strenuous exercise (Pedersen & Hoffman-Goetz, 2000). Though to date there is still a lack of direct casual evidence between these symptom effects and exercise induced immune system changes.

Righto, you have decided you have a cold therefore a light training session is in order and not the strenuous interval session you had on the training schedule. Is there anything that you can take to speed up recovery? A number of nutritional supplements have been studied such as glutamine, antioxidants such as vitamin C, and carbohydrates, all of which have been shown to influence immune variables and therefore have the potential to influence exercise associated immune function (Pedersen & Hoffman-Goetz, 2000). More recently there has been an increase interest in herbal remedies such as Echinacea but there is very limited scientific data on these.

Though all of these substances have the potential to assist immune function, due to the complex nature of the interaction between exercise, immunity and infection, any one nutritional supplement is unlikely to be on substantial benefit on its own. A combination of these may be the best means of attack.

So what’s the best policy when suffering from the common cold?

# Any inkling of the dreaded early warning signs - abide by and head to bed; else:

# Light training only, stay away from anything strenuous and don’t feel bad about missing the planned training sessions.

# Take carbohydrates during any light training session.

# Take plenty of fluid both during and after training.

# Take some Vitamin C, and Echinacea

# Try and stay away from anything stressful at work or home

References

Pedersen, B., & Hoffman-Goetz, L. (2000). Exercise and the immune system: regulation, integration, and adaptation. Physiol Rev, 80(3), 1055-1081.

# Eccles, R. (2002). An explanation for the seasonality of acute upper respiratory tract viral infections. Acta Otolaryngol. 122 (2), 183-91.

# Pedersen, B., Bruunsgaard, H., Jensen, M., Krzywkowski, K., & Ostrowski, K. (1999). Exercise and immune function: effect of ageing and nutrition. Proc Nutr Soc, 58(3), 733-742.
Pedersen, B., & Hoffman-Goetz, L. (2000). Exercise and the immune system: regulation, integration, and adaptation. Physiol Rev, 80(3), 1055-1081.