Effects Of Oral Administration Of Caffeine On The Salivary Immunoglobulin A And Lysozyme In Male Endurance Collegiate Players During Exercise In A High-temperature Environment

Objective: The objective of this study was to examine the effects of oral administration of caffeine on the salivary secretory immunoglobulin A(slg A) and lysozyme(LZM) in male endurance collegiate players during prolonged exercise in a high-temperature environment.Methods: This study used experimental method, and thirteen male endurance collegiate athletes were used as subjects. Each subject finished two trials including caffeine exercise trial and control exercise trial in a laboratory room with the temperature of 33? and the relative humidity of 65%. In each trial, subjects exercise at 50% maximal workload for 40 minutes on a cycle ergometer at a pedaling cadence of 60 rmp. In each of the caffeine exercise trial, subjects drank sports drink(3ml/kg body mass) containing caffeine(6mg/kg body mass); while in the control exercise trial subjects drank the same amount of sports drink. During each trial, saliva samples were collected at the points of 60 min before-exercise, before-exercise, exercise 20 min, and after-exercise. Salivary s Ig A and LZM were determined, and secretion rates of s Ig A and LZM were calculated.Results:(1) In the caffeine exercise trial and control exercise trial, the s Ig A concentration of after-exercise(4.6614±1.0908?g/ml, 5.8036±2.0464?g/ml) were significantly higher than that of 60 min before-exercise(3.9156±0.6659?g/ml, 4.1126±0.9469?g/ml), respectively(P <0.05). There were no significant differences in the concentrations and the secretion rates of s Ig A at the different time points between caffeine exercise trial and control exercise trial(P>0.05).(2) In the caffeine exercise trial and control exercise trial, the LZM concentration of after-exercise(9.3553±3.9648?g/ml, 18.1758±15.3318?g/ml) were significantly higher than that of 60 min before-exercise(4.7993±3.0142?g/ml, 6.4549±5.9372?g/ml), respectively(P <0.05). The LZM concentration of after-exercise in the caffeine exercise trial(9.3553±3.9648?g/ml) was significantly lower than that in the control exercise trial(18.1758±15.3318?g/ml)(P <0.05). The secretion rates of LZM of exercise 20 min, and after-exercise(8.7542±6.2113?g/min,12.3359±7.4076?g/min) were significantly lower than those in the control exercise trial(16.7278 ± 15.4061?g/min, 20.9404 ±21.2443?g/min)(all P <0.01).(3) In the caffeine exercise trial, the concentrations of s Ig A correlated positively with the concentrations of LZM(r=0.598, P <0.01), and the secretion rates of s Ig A correlated positively with the secretion rate of LZM(r=0.598, P <0.01). In the control exercise trial, the concentrations of s Ig A correlated positively with the concentrations of LZM(r=0.924, P <0.01), and the secretion rates of s Ig A correlated positively with the secretion rates of LZM(r=0.825, P <0.01).Conclusions:(1) Oral administration of caffeine does not affect the level of salivary s Ig A, but decreases the level of salivary LZM in male endurance collegiate players during exercise in the high-temperature environment.(2) The prolonged moderate intensity exercise in the high-temperature environment increases the levels of salivary s Ig A and LZM, thus enhances function of mucosal immunity.(3) There exists a strong positive correlation between concentrations of salivary s Ig A and LZM in male endurance collegiate players during exercise in the high-temperature environment..