Cheng Lin, Wang Hongli, Han Yanbai
College of Physical Education and Health, Guangxi Normal University, Guilin, China.
Front Nutr. 2022 Nov 15;9:973003. doi: 10.3389/fnut.2022.973003. eCollection 2022.
Caffeine is commonly used by athletes as an energy supplement, but studies on its effects on salivary antimicrobial proteins (sAMPs) in humans during exercise are rare with ambiguous findings. It is also still controversial whether hot environments affect sAMPs. Using a double-blind, randomized crossover design, we examined 12 endurance-trained male collegiate athletes who completed the following two experiments: a caffeine experiment (CAF) and a placebo experiment (PLA). The participants acutely consumed caffeine-containing (6 mg/kg body weight) sports drink (3 ml/kg body weight) or an equivalent amount of placebo sports drink and subsequently performed cycling exercise for 40 min in the heat (33 ± 0.24°C, 64 ± 2.50% relative humidity) at 50% of maximum output power, maintaining a pedal frequency of 60 rpm. Saliva was collected at 60 min pre-exercise (T), the start of exercise (T), 20 min of exercise (T), and the end of the exercise (T), and salivary α-amylase (sAA) and lactoferrin (sLac) were tested. The rating of perceived exertion (RPE) was measured at T-T, while core body temperature (T ) and heart rate (HR) were monitored continuously. T , HR, and RPE increased with time during the exercise ( < 0.01), with no difference in T and HR between the CAF and PLA ( > 0.05), but RPE was higher in the PLA than in the CAF ( < 0.05). sLac concentrations were significantly higher at T and T than at T ( < 0.01) and higher at T than at T and T ( < 0.01), with no difference between the CAF and PLA ( > 0.05). Compared with T, sAA activity was significantly increased at T, T, and T ( < 0.01). sAA activity was significantly higher at T than at T and T ( < 0.01), at T than at T ( < 0.05), and in the CAF than in the PLA ( < 0.01). Heat stress caused by acute exercise in hot environments did not impair the sAMPs parameters of the participants. Instead, the participants showed transient increase in sAA activity and unchanged sLac concentrations. Caffeine may increase salivary markers related to immune response during exercise.
咖啡因是运动员常用的一种能量补充剂，但关于其在运动过程中对人体唾液抗菌蛋白（sAMPs）影响的研究很少，且结果不明确。热环境是否会影响sAMPs也仍存在争议。我们采用双盲、随机交叉设计，对12名受过耐力训练的男性大学生运动员进行了研究，他们完成了以下两个实验：咖啡因实验（CAF）和安慰剂实验（PLA）。参与者急性摄入含咖啡因（6毫克/千克体重）的运动饮料（3毫升/千克体重）或等量的安慰剂运动饮料，随后在高温环境（33±0.24°C，相对湿度64±2.50%）下以最大功率输出的50%进行40分钟的骑行运动，保持踏板频率为60转/分钟。在运动前60分钟（T0）、运动开始时（T1）、运动20分钟时（T2）和运动结束时（T3）收集唾液，并检测唾液α-淀粉酶（sAA）和乳铁蛋白（sLac）。在T1 - T3期间测量主观用力程度（RPE），同时持续监测核心体温（T c）和心率（HR）。运动过程中T c、HR和RPE随时间增加（P < 0.01），CAF和PLA之间的T c和HR无差异（P > 0.05），但PLA组的RPE高于CAF组（P < 0.05）。sLac浓度在T1和T3时显著高于T0（P < 0.01），在T3时高于T1和T2（P < 0.01），CAF和PLA之间无差异（P > 0.05）。与T0相比，sAA活性在T1、T2和T3时显著增加（P < 0.01）。sAA活性在T3时显著高于T1和T2（P < 0.01），在T2时高于T1（P < 0.05），且CAF组高于PLA组（P < 0.01）。高温环境下急性运动引起的热应激并未损害参与者的sAMPs参数。相反，参与者的sAA活性出现短暂增加，sLac浓度未改变。咖啡因可能会增加运动过程中与免疫反应相关的唾液标志物。
