It's winter, the nights have drawn in, it's cold, damp and miserable, but you've only got a couple of months to the start of the new season. So you need to go training, but the weather is awful. The question is; are you more likely to make yourself ill with all this training and what about the bad weather?

In the United States the Centre for Disease Control and Prevention estimate that more than 425 million cases of colds and 'flu occur annually. It's likely that a similar story (depending on population size) occurs in other countries. This year in the UK there has been a reported increase in 'flu cases.

Cold or 'Flu?
You wake up one morning and feel like death. Your head is hurts, you feel congested and unable to breathe properly, your body doesn't feel like it belongs to you – you must have the 'flu? Right? Maybe, maybe not. So how do you differentiate between colds, and 'flu? Here's some background:

Both colds and influenza ('flu) are caused by viruses
A cold is an inflammation of the upper respiratory tract, whereas 'flu affects the whole body
There are more than 200 different types of viruses from the family of rhinoviruses and corona viruses, which initiate colds. With this many you can't become immune to them
Influenza is caused by two major strains of virus, with a third minor strain. Known as A, B (major) and C. The strains of virus are continually changing which makes it impossible to become immune. Furthermore, 'flu vaccines are scientists guessing at which strain is likely to be most prevalent that year
Similarities between colds and 'flu are chest congestion and cough
Cold symptoms usually include sneezing, sore throat, coughing, chest congestion and nasal congestion
Influenza symptoms usually include pyrexia (high fever), a pounding headache, severe aches and pains, fatigue and general lethargy. Often 'flu victims are laid up in bed for several days

Do athletes have a greater chance of becoming ill?
Whilst, many coaches and athletes themselves feel that athletes' suffer a greater risk of illnesses such as cold, 'flu, chest infections, etc., popular belief has it that athletes are less likely to be ill. There has been a fair amount of research into exercise and upper respiratory tract infections (URTI). Research by Nieman (1994) suggests that a vague 'J' shaped model exists between exercise and infection (shown below).


This figure suggests that with moderate amounts of exercise the immune system is strengthened, whilst with heavy training (e.g. characterised by intense cycle training; multisport training) the immune system is weakened and there is a greater chance of an upper respiratory tract infection.

Effects of exercise on the immune system
Recent research has suggested that with high intensity endurance training there is a biphasic perturbation of the circulating leukocyte count. Immediately post exercise leukocytes increase 50 % - 100%. However, within 30 minutes of recovery, the lymphocyte count dips 30 - 50% below pre exercise levels, and remain low for 3 - 6 hours. Lymphocytes are white blood cells that either destroy invading organisms or produce antibodies that deal with the invading organisms.

Lymphocyte changes are dependent upon exercise-induced changes in adrenaline (U.S. epinephrine) and cortisol. Concentrations of adrenaline and cortisol rise rapidly at intensities greater than 60 % VO2 max (the maximal volume of oxygen that can be utilised by the body). Post exercise, blood concentrations of adrenaline start to fall to pre exercise levels almost immediately. This is in contrast to cortisol, which can remain elevated for more than 2 hours. Following heavy training there is a general impairment of the immune system. This would leave athletes vulnerable to infection such as colds and 'flu.

Prevention of infection
So how do you prevent infection and can you reduce the chance of getting ill? Viruses are everywhere and leaving yourself vulnerable to attack can increase the incidence of illness. We've just seen that intense endurance exercise can leave you open to attack. Touching, for instance, your eyes, nose or mouth, can easily spread diseases; therefore, you should clean your hands compulsively to prevent the spread of infection.

The volume of training that an athlete completes can also have a bearing on the chance of becoming ill. Nieman et al., reports that in a group of marathon runners it was found that those running more than 96 kilometres per week doubled their odds of becoming ill compared with those training less than 32 kilometres per week. Interestingly, those who competed in the marathon had a 6 to 1 chance of becoming ill (some people ended up not taking part in the marathon).

In another study (Heath et al., 1991) runners self reported URTI symptoms over a year. It was found that on average the runners experienced 1.2 URTI episodes per year. However, those who ran less than 16 kilometres per week had had the lowest odds for becoming ill. At more than 27 kilometres per week the odds doubled, suggesting that as volume is increased so is the chance of infection.

Surprisingly, there is also a link between psychological stress and the immune system. During episodes of psychological and emotional stress periods there is an increase in circulating adrenaline, cortisol, and neuropeptides, which will have a detrimental effect on the immune system. Furthermore, during racing there is often psychological stress, which might further affect the immune system.

Nutritional supplementation
Can the use of nutritional supplements help improve the immune response to exercise? Recently, glutamine (a non essential amino acid) has been touted as the wonder aid for improving immune response following exercise. Glutamine metabolism is of vital importance for lymphocytes. A decreased amount of glutamine has a direct effect on lowering the proliferation of lymphocytes. Exercise can decrease the amount of glutamine. However, research has failed to completely satisfy whether exercise induced reductions in glutamine is correlated to decreased immunity.

More interesting results have been noted with carbohydrate (CHO) supplementation. During exercise as CHO is oxidised and muscle glycogen is used and depleted, stress hormones are released that depress the immune system. By using a CHO drink during and post exercise, plasma glucose concentration is better maintained and changes in immunity are reduced. Furthermore, CHO supplementation may be protein sparing, thus preserving adequate muscle glutamine levels.

Recent research (Peters-Futre, 1997) has shown that several double-blind, placebo, studies of South African ultramarathon runners have demonstrated an association between vitamin C supplementation and fewer reports of URTI symptoms. However, other studies have failed to show similar responses. Research compiled by Holford (1997; founder of the Institute of Optimum Nutrition) has suggested that 3grams of vitamin C every 4 hours for a total of 48 hours has a beneficial effect on the immune system when ill. However, these high doses of vitamin C supplementation may cause a laxative effect. Furthermore, in the book "The Optimum Nutrition Bible" Holford suggests that taking 1 gram per day of vitamin C has a positive effect on the immune system.

The micronutrient zinc has also recently been investigated in terms of benefiting the immune system there is however, a paucity of data. In eight recent controlled trials examining the use of zinc on the common cold, the results are equivocal. Four studies showed a positive benefit, whilst the other four did not, some of which is attributed to the methodology employed in the studies concerned. The exact mechanism(s) for zinc exhibiting a positive effect has still to be fully elucidated, however, one hypothesis is that zinc prevents the rhinovirus from binding to respiratory molecules.

The use of herbs is becoming more commonplace in the treatment of many illnesses. It is thought that echinacea can help speed the recovery from certain respiratory illnesses, such as cold and 'flu. Again there is a paucity of data with equivocal results, but there is growing evidence to support it's use.

To exercise or not?
Okay, so you're ill, do you train or not? Whilst, this information should not take the place of a qualified medical practitioner, here are some guidelines.

Exercising during the incubation period of an infection may worsen the illness
If an athlete experiences sudden and unexplained decrease in performance during training or competition, a viral infection should be suspected
If it appears that an infection is beginning, then training/competing should either be suspended or greatly reduced. Often, at the beginning of an illness there is a rise in resting heart rate, usually larger than that associated with poor recovery from training (e.g. > 10 b min-1) 
Light, low intensity exercise during sickness with a common cold is not contraindicated, providing symptoms are above the neck
If there are signs or symptoms of systemic involvement (e.g. pyrexia, fatigue, muscle aches, swollen lymph glands, etc.) as in 'flu or symptoms of a 'chest' infection (hacking cough, 'dirty' phlegm, pyrexia, etc.) then 2 weeks post illness should be allowed before resuming intensive training to avoid relapse and / or potential life threatening complications such as cardiomyopathy or endocarditis
Remember that these common diseases (colds, 'flu, chest infections, etc.) are all potentially serious and life threatening. Don't ignore the symptoms. If in doubt, leave it out - don't train.

Although there isn't a definitive list of substances that can be taken to improve/prevent [respiratory] illnesses or one that is 100% scientifically proven, here's what I do or try to do:

Avoid contact with 'ill' people (contact spreads infection) especially post training and racing
Avoid stress
Avoid overtraining
Get a 'flu vaccination
Eat a 'healthy' diet, including plenty of fresh fruit and vegetables
Take a '100%' daily multi-vitamin and mineral as well as 1000 mg of vitamin C
Take a carbohydrate drink during and post training (e.g. PSP 22) and / or a carbohydrate-protein 'recovery' drink after an intensive session (e.g. REGO)

At the onset and during illness
Increase vitamin C intake to 3 x 1000mg per day; spread evenly throughout the day
Use zinc lozenges
Use echinacea
Decrease or stop training depending on symptoms
Don't feel guilty about not training
Drink plenty of fluids
Steam inhalation for nasal congestion

Hopefully, you'll all get through every season without being ill... Take care.

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*This article is for educational purposes only. Before, embarking on any exercise regimen you should be fit, healthy and free from any illness/disease. If you have any queries or are not sure about your general health and well being, you should contact your health care advisor/family physician.

HealthRichard Stern