Immune responses to exercising in a hot environment in soccer players

Hot temperature and exercise independently lead to metabolic changes in the human body and depress the immune system. Changes on immunoglobulin A (IgA) and cortisol in response to an intensive exercise in hot environment especially in the soccer players are not well known. Thus, the aim of this study was to investigate the effect of an intensive exercise in thermoneutral and hot conditions on salivary IgA (s-IgA) and cortisol concentrations in soccer players.

Twelve elite male soccer players (age, 21 to 34 years) participated in this study as the subject. Total unstimulated saliva samples were collected before, immediately and 30 min after the exercise training in thermoneutral (HT: 20 ○C and 20% RH) and hot environments (HT: 30 ○C and 20% RH). Water was available ad-libitum.

s-IgA and cortisol levels were increased after an intensive exercise at both environments and their levels were significantly higher than baseline until 30 min after the exercise (P<0.05). Total protein concentration was increased 30 min after the exercise in the heat (P<0.05), however no significant differences were observed between two occasions. Salivary flow rate was not affected by 2 conditions or differed at any time-point post-exercise. No significant differences were observed in s-IgA and cortisol levels between two environments.

In conclusion, enduring hot temperature intensified stressful responses elicited by intensive exercise. This study advocates that hot temperature deteriorates exercise performance under exhaustive stress and effort conditions in soccer players.