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IntroductionLysozyme is one of the salivary antimicrobial proteins which act as the “first line of defence” at the mucosal surface. The effects of prolonged exercise in the hot and cool environments among recreational athletes on salivary lysozyme responses are very limited in the literature, especially in the Asian countries.ObjectiveTo determine the effects of prolonged running in the hot and cool environments on selected physiological parameters and salivary lysozyme responses among recreational athletes.MethodsRandomised and cross-over study design. Thirteen male recreational athletes (age: 20.9 ± 1.3 years old) from Universiti Sains Malaysia participated in this study. They performed two separate running trials; 90 min running at 60% of their respective maximum oxygen uptake (trueV˙normalO2max) One running trial was performed in the hot (31ºC) while the other was in the cool (18ºC) environment and this sequence was randomised. Each running trial was started with a 5 min warm-up at 50% of participant's respective trueV˙normalO2max Recovery period between these two trials was one week. In the both trials, saliva samples, blood samples, heart rate, ratings of perceived exertion, skin and tympanic temperatures, oxygen consumption, nude body weight, room temperature, and relative humidity were collected.ResultsParticipants' skin temperature, tympanic temperature, body weight changes, heart rate, ratings of perceived exertion, and plasma volume changes were significantly higher (p < 0.05) in the hot trial compared to the cool trial. Saliva flow rate was not significantly (p = 0.949) different between the hot (0.32 ± 0.08 ml/min) and cool (0.27 ± 0.05 ml/min) trials. However, in each trial, it significantly decreased (p < 0.05) at post-exercise as compared to pre-exercise but it returned to baseline value at 1 h post-exercise. In addition, there were no significant differences between and within hot and cool trials in salivary lysozyme concentration (p = 0.925; 4.79 ± 1.37 and 4.44 ± 1.11 μg/ml respectively) and secretion rate (p = 0.843; 1.67 ± 1.1 and 1.17 ± 1.0 μg/min respectively).ConclusionThis study found similar lysozyme responses between both hot and cool trials. Thus, room/ambient temperature did not affect lysozyme responses among recreational athletes. Nevertheless, the selected physiological parameters were significantly affected by room temperature.

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.