Abstract
Athletes are susceptible to upper respiratory tract infection (URTI) during intense
training and after major competition; high rates of URTI have also been associated
with the overtraining syndrome (staleness). Secretory Immunglobulin A (IgA), the predominant
Immunoglobulin in mucosal secretion, is a major effector of resistance against pathogenic
microorganisms causing URTI. Previous work has shown that salivary IgA levels decrease
after a single bout of intense prolonged exercise. The purpose of these studies was
to examine the IgA response to various exercise conditions. Whole, unstimulated saliva
was obtained before and after exercise. IgA concentration (ug.mg protein-1) was measured by ELISA and IgA secretion rate (µg · min-1) calculated. Study 1: Recreational joggers ran on a treadmill for 40 min at 55% and 75% VO2peak, and competitive distance runners ran for 90 min at the same intensities. In both
groups, IgA secretion rate did not change significantly after exercise at either intensity.
Study 2: Competitive runners ran on a treadmill for 90 min at 75% VO2peak on 3 consecutive days. IgA secretion rate decreased 20 to 50% after exercise (p<.001).
Post-exercise IgA secretion rates were significantly lower (p<.05) on days 2 and 3
compared with day 1. Study 3: Elite swimmers were followed over a 6 month season, with IgA concentration measured
at 5 times. Throughout the season, IgA concentration was significantly (p<.05) lower
in stale compared with well-trained swimmers. Taken together, these data suggest that
exercise intensity is an important factor determining the mucosal immune system response
to exercise; intense daily exercise appears to have a cumulative effect on mucosal
immunity. Exercise-induced changes in IgA output may be one mechanism responsible
for the high incidence of URTI among athletes who undertake intense exercise on a
daily basis.
Key words
Upper respiratory tract infection - colds - intense exercise - secretory immunoglobulin
A - mucosal immunity - immune function
