Exercise And Immunity: Infection and swimming performance

Exercise And Immunity: Infection and swimming performance

The persuasive theory that heavy training lowers immunity to illness, with a consequent negative impact on performance, has been called into question by an Australian study of elite male and female swimmers. This showed that a season of training did not alter salivary immunoglobulin concentrations and, further, that the presence of respiratory tract infection had no significant impact on competitive performance.

Exercise and training by highly-trained athletes have been shown in previous studies to elicit changes in mucosal immunity, particularly in lowering levels of the secretory immunoglobulins IgA and IgM. The researchers responsible for this study were less interested in substantiating these earlier results than in finding out whether such changes lead to parallel changes in the incidence of illness and whether, in turn, such illness has any impact on competitive performance, an assumption which has not yet been tested experimentally.

The study centred on members of the 1998 Australian National Swimming Team during the four-month run-up to that year's Commonwealth Games (CG) in Kuala Lumpur, Malaysia. A team of 41 swimmers aged 15-27 were monitored between May and August, alongside a control group of 25 coaching and support staff who were exposed to the same environmental conditions - minus the training, of course!

At the start of the study, one week after the Australian National Swimming Championships in Melbourne, all the team members provided saliva samples for immunoglobulin assessment. They were then retested after a further 15 weeks of training, 17 days before the start of the Games. Episodes of respiratory illness and infection were investigated and recorded by the team physician in the six-week taper period before and including the CG swimming competition. Competitive performance of the swimmers at the National Championships (May) and the CG (September) was assessed and compared in the light of illness history and immune status as revealed by salivary immunoglobulin concentrations.

In the event, the Australian Swimming Team won a total of 48 medals (24 gold) to be the leading nation in the CG swimming competition, with a mean international point score of 947, compared with 945 at the National Championships.

There was a significant incidence of single episodes of illness in the taper and competition period of the CG, affecting 42% of all subjects. But symptoms were mostly mild, only three swimmers were actually ill during the competition week and all were sufficiently healthy to compete in their selected events.

Despite the intensive training undertaken by the swimmers between May and August, there was no significant change in salivary IgA and IgG concentrations and only small differences in salivary IgM, which is at odds with some previous research. And there were no significant differences in immune markers between healthy and ill swimmers. However, the same comparison between healthy and ill coaching and team staff revealed that staff with illness had significantly lower salivary IgG in May than their healthy counterparts, while during the August assessment staff with illness had a significantly lower median salivary IgA concentration - about one third the levels of healthy staff.

This was an unexpected finding, since the researchers had assumed that the highly trained athletes would be more prone to lowered immunity and illness than the relatively sedentary control group. ''The incidence of RTI and lowered mucosal immunity suggests the involvement of psychological and lifestyle issues rather than physiological factors in the regulation of effective immunity in this group,' they comment. The greater age of the controls may also have been a factor. 'A number of studies have suggested a link between psychological stress and the incidence of illness. Coaching at the elite level can be very stressful, and the results of this study suggest that lifestyle and self-management programmes should be directed to coaching and team staff as well as the athletes themselves.'

Did illness in the swimmers impair their performance? The healthy swimmers did score better than the ill swimmers, with mean International Points Scores (IPS) of 955 and 937 respectively. In scientific terms this difference did not reach statistical difference; but in real-world terms it was enough to change a swimmer's placing from a first, second or third position to a minor or non-medal finishing position (fourth to eighth).

The researchers' final conclusion is that more studies are needed to clarify the relationship between illness and competitive performance in elite athletes.
Med Sci Sports Exerc 2001 Mar 33(3) 9348-53

Vitamin C for biathletes
Taking high doses of vitamin C does not correct impaired immune function after strenuous exercise, according to a small-scale study of Austrian biathletes. The study was carried out during the gruelling 'Schockel Classic' in Graz, consisting of 16.5k uphill cycling and 2k uphill running, with a total difference in altitude of 1100m. Six male athletes took high doses of vitamin C (2g/day) for a week before the race while a further four male competitors had no supplementation and served as controls. Blood samples were taken 15 minutes before and immediately after the biathlon, for which the subjects' times ranged from 1hr 7min to 2hr 23min.
The researchers were most keen to analyse the effect of vitamin C on the functioning of neutrophils, the while blood cells which respond most rapidly to invasion of the body by viruses or bacteria. Although neutrophils in blood are actually elevated after exercise, an impairment of neutrophil function has been suggested as a factor in the increased susceptibility of athletes to upper respiratory tract infections (URTI). Treatment with vitamin C is thought to improve neutrophil function in patients with recurrent furunculosis (boils caused by persisting bacteria in the skin) and to prevent URTI in patients after strenuous exercise.
Analysis of blood samples after the race showed evidence of impaired neutrophil function in all the athletes, with no difference between those taking vitamin C and the controls.
Raised blood levels of the 'stress hormones' noradrenaline and adrenaline, which have been shown to impair neutrophil function in laboratory tests, were observed in all the athletes and were inversely correlated to neutrophil function, with no difference between supplemented athletes and controls.
'Our results do not support the concept that vitamin C supplementation corrects neutrophil dysfunction after strenuous exercise,' comment the researchers. The evidence for its efficacy has come from studies of people with already-impaired neutrophil function. 'As none of the athletes in our study showed any neutrophil impairment before the biathlon, this may explain the lack of effect of vitamin C treatment. Therefore, in athletes without evidence for pre-existing impaired neutrophil function, vitamin C supplementation with the aim to correct exercise-induced impaired neutrophil function cannot be recommended.'

Another argument against supplementation with high doses of vitamin C comes from a new US study, published in Science, which ratifies previous British findings that taking high levels of vitamin C (500mg/day) could lead to the production of 'genotoxins' which can damage DNA.
Eur J Clin Invest 2001 Mar 31(3) p258-63