Effects of Prolonged Exercise in the Heat and Cool Environments on Salivary Immunoglobulin A among Recreational Athletes

This study aims to determine the effects of prolonged exercise in the heat (31°C) and cool (18°C) environments on salivary Immunoglobulin A (SIgA) among recreational athletes. Thirteen healthy male participants (age: 20.9 ± 1.3 years old) were recruited and randomised in this cross-over study. In this study, participants performed the exercise trials in the heat environment at 31°C first followed by another exercise trial in the cool environment trial at 18°C or vice versa with one week of recovery period. Physiological parameters (heart rate, body weight changes and oxygen uptake) as well as room temperature and relative humidity were recorded. Cool water (3 ml.kg -1 body weight) was given to the participants at every 20 min during both exercise trials. Saliva samples were collected to calculate the saliva flow rate and analysed for salivary Immunoglobulin A (SIgA) concentrations and secretion rate. Paired t-test and two-way ANOVA with repeated measures were performed to analyse the data. The results revealed that saliva flow rate, SIgA concentration, and SIgA secretion rate did not significantly different between exercise trial in the heat and in the cool environments. However, prolonged exercise significantly decreased (p < 0.05) saliva flow rate in both trials with the values return to baseline 1 h post exercise. Salivary IgA concentration and secretion rate were not affected by prolonged running. As a conclusion, SIgA responses did not affected by ambient/room temperature. In addition, prolonged exercise with adequate fluid intake during exercise did not supress SIgA responses thus may not increase infection risk among athletes.