Infectious Disease

Effects of exercise on immunity

Benefits

Regular, moderate levels of exercise improve resistance to most infections, particularly those affecting the upper respiratory tract (URTI).

Possibly because of mild elevations in:

T-cell lymphocytes.
Interleukins.
Endorphins.

Adverse effects

There is good evidence that athletes undertaking intensive training (e.g. endurance runners covering > 90km/week) are more prone to minor infection, particularly URTI. This is thought to be due to reduction of:

Salivary IgA, which plays an important role in resistance to some viruses.
IgM.
Natural killer cells, which show increased activity during exercise, only to fall in the first few hours of recovery.

Supplementation with carbohydrate, vitamin C, glutamine, and zinc may reduce the immunosuppressive effect of heavy exercise.

Why are athletes prone to infection?

Stress/overtraining/under recovery

Symptoms may include:

Poor performance.
Depressed mood.
Insomnia.
Frequent URTIs.
Cervical lymphadenopathy may be present.
High cortisol or low testosterone levels are sometimes seen.
Lack of recovery time in training programmes can lead to lowered IgA levels, reducing resistance to viral infection, and lowered T and B lymphocytes (cortisol driven).

High level and endurance athletes are particularly at risk of training excessively, due to their competitive nature.

Treatment includes rest and education about the need for increased training recovery time, optimization of nutrition, psychological monitoring and support, and gradual re-introduction of training.

Close contact with other athletes

On tours and in training/competition camps, the inevitable close contact between athletes, coaches, and support staff can encourage the spread of respiratory and GI infections.

Sexual activity

Like the population as a whole, athletes are at risk of sexually-transmitted diseases if practicing unsafe sex.

Trauma

Traumatic injury can predispose to infection, especially if wounds are open.

Foreign travel

Hepatitis B is endemic in many third world countries, and travelling athletes should be considered for immunization (particularly in contact sports). Travel also carries risk of tropical diseases, such as malaria and diarrhoea.

Upper respiratory tract infections

Although a small proportion of URTIs will be caused by group A streptococcus, most are caused by a virus such as:

Echovirus.
Adenovirus.
Coxsackie viruses A and B.
Influenza.

Investigations may include a throat swab and a monospot or Paul-Bunnell test for infectious mononucleosis (glandular fever).

Treatment of URTIs

Analgesia: paracetamol—effective and safe in correct dosage.
Decongestants: nasal sprays can help. Doctors and sports people need to be aware that some decongestants are still on the WADA banned list and, if in doubt, the drug should be checked using the UK sport drug information database. Menthol or eucalyptus inhalants will relieve most symptoms of congestion and are not banned.

Dangers of URTIs

Coxsackie virus can cause inflammation of heart muscle (myocarditis) in exercising athletes. If a sports person has a combination of the following symptoms, they should be advised not to train or play:

Resting tachycardia (> 10beats/min above normal).
Myalgia.
Lethargy.
Oral temperature > 38*C.
Cervical lymphadenopathy.

Advise athlete that premature return to training/playing will delay recovery and there is a small risk of myocarditis and cardiac arrhythmias.

‘Neck check’ guidelines for athletes

If all of the symptoms are above the neck (stuffy or runny nose, sneezing, watery eyes, and/or scratchy throat), it is okay to start your usual workout at about half speed.
Do not work out if you have a fever or symptoms below the neck (aching muscles, a hacking cough that seems to resound deep within the chest, nausea, vomiting, and/or diarrhoea). Working out under those conditions is risky, and you’ll recover much faster from your illness if you rest.¹

Common viral infections

These can be caused by several viruses, particularly:

Epstein-Barr virus (infectious mononucleosis).
Toxoplasma.
Cytomegalovirus (CMV).
Primary HIV disease.

They commonly occur in younger age groups, and are linked to the development of chronic fatigue syndrome. Splenomegaly occurs and participation in contact sports carries a risk of traumatic splenic rupture.

Infectious mononucleosis (InfM)