ORIGINAL ARTICLE Panagiota Klentrou ® Thomas Cieslak Melanie MacNeil ® Angela Vintinner ® Michael Plyley Effect of moderate exercise on salivary immunoglobulin A and infection risk in humans Accepted: 12 February 2002 / Published online: 17 April 2002 Ó Springer-Verlag 2002 Abstract The incidence of upper respiratory tract in- fections (URTI) and salivary immunoglobulin A con- centrations [IgA s ] of nine individuals were examined during 12 weeks of moderate exercise training, and compared to ten sedentary controls. Changes in maxi- mal oxygen uptake were assessed at initial, mid-point and final evaluations (T1–3), while changes in [IgA s ] and salivary immunoglobulin concentration-salivary albu- min concentration ratio ([IgA s ]:[Alb s ]) were monitored at T1 and T3. During the 12 week period, symptoms of URTI were self-recorded daily. During the period of training the level of fitness significantly increased (P<0.05) in the exercise group. The number of days recording symptoms of influenza, but not of cold, and total light URTI symptoms was significantly reduced in the exercise group during the last weeks of training. A significant increase in [IgA s ] and in [IgA s ]:[Alb s ] was found in the exercise group after training. Both [IgA s ] and [IgA s ]:[Alb s ] were significantly related to the number of days showing symptoms of influenza (P<0.01) and the total number of days of sickness (P<0.05). These data provide quantitative support for the belief that regular, moderate exercise results in an increased [IgA s ] at rest and [IgA s ]:[Alb s ], which may contribute to a de- creased risk of infection. Keywords Salivary immunoglobulin A:albumin ratio ® Upper respiratory tract infection ® Immunosurveillance ® Aerobic training Introduction Intense exercise has been linked to a generalized lower- ing of the body’s natural defence mechanisms through suppression of natural killer cell (NK-cell) activity (Nieman 1994), neutrophil activity (Hack et al. 1994), inteleukin-2 concentrations (Baj et al. 1994), inhibition of B- and T-lymphocyte function (Nieman 1994), and immunoglobulin A concentrations ([IgA]) (Tharp and Barnes 1989; Mackinnon 1996). On the other hand, a regular exposure to exercise at the level of moderate training is believed to lead to a decrease in one’s sus- ceptibility to contracting an upper respiratory tract in- fection (URTI) (Nieman et al. 1990; Smith et al. 1990; Karper and Goldfarb 1995; Harjee 1996; Weidner et al. 1998), and therefore, a decreased incidence of URTI (Woods et al. 1999). Nieman (1994) has described the relationship be- tween the risk of contracting an URTI and the amount of regular exercise as being a ‘‘J–curve relationship’’. Thus, a sedentary individual would be at moderate risk of contracting an URTI, an individual who is slightly to moderately active (regularly) would exhibit a decreased risk of contracting an URTI, and one who is highly and intensely active would show an increased risk above that of the sedentary individual (Nieman 1994). This hy- pothesis has been supported by previous studies which allowed for differences in the lifestyles and activity levels of the participants (Nieman et al. 1990, 1993, 1998; Heath et al. 1991). To date, the majority of the research has been con- ducted on subjects who are highly trained athletes or individuals who regularly train intensely. Evidence points to an increased incidence and contraction of URTI in these individuals (Peters and Bateman 1985; Nieman and Pederson 1999). Immunoglobulin A (IgA) has been shown to be active in defending against infectious agents. Mackinnon (1996) reports that the IgA class of antibodies primarily interact and defend the various secretory surfaces from invasion; therefore, [IgA] can readily be measured in tears, saliva, or fluids from the respiratory, genito-uri- nary and gastro-intestinal tracts. Although heavy exer- cise has been shown to decrease markedly the IgA concentrations of both nasal and salivary ([IgA s ]) Eur J Appl Physiol (2002) 87: 153–158 DOI 10.1007/s00421-002-0609-1 P. Klentrou (&) ® T. Cieslak ® M. MacNeil ® A. Vintinner M. Plyley Faculty of Applied Health Sciences, Brock University, St. Catharines, Ontario L2S 3A1, Canada E-mail: nota@arnie.pec.brocku.ca Tel.: +1-905-6885550 Fax: +1-905-6888364