PDF(Pubmed)
Abstract：
While previous studies have explored a range of factors governing the optimal use of caffeine (CAF) in athletes, limited research has explored how time of day (TOD) affects the ergogenic effects of various CAF dosages on physical performance. This study aimed to increase knowledge about how different recommended CAF doses (3 mg/kg vs. 6 mg/kg) ingested at different TODs affected maximal high-intensity physical performance and the perception of potential side effects in female athletes. In this double-blind, randomized, and counterbalanced study, 15 low CAF consumer athletes (aged 18.3 ± 0.5 y) underwent six trials, including three testing conditions assessed across two TODs: one in the morning (08:00 a.m.) and one in the evening (06:00 p.m.). During each condition, the participants ingested either a placebo, 3 mg/kg CAF (CAF (3 mg)), or 6 mg/kg CAF (CAF (6 mg)) capsules 60 min before each test with an in-between washout period of at least 72 h. In each trial, the participants performed a countermovement jumps test (CMJ), a modified agility t test (MATT), a repeated sprint ability (RSA), a rating of perceived exertion (RPE), and finally, a CAF side effects questionnaire. Our findings indicate the absence of an ergogenic effect on CMJ, MAT, and RSA performance in the evening after administering CAF (3 mg) or CAF (6 mg) compared to a placebo. Likewise, when CAF was ingested in the morning, there was an improvement in these performances with both CAF (3 mg) and CAF (6 mg), with greater improvement observed after CAF (6 mg). Additionally, neither the CAF dosage nor the TOD had a significant effect on the RPE. The occurrence of side effects increased significantly after the evening ingestion of CAF, particularly with a moderate dose of CAF (6 mg). Our findings indicate that the effectiveness of CAF depends on the TOD and CAF dosage. When ingested in the morning, a moderate dose of CAF (6 mg), rather than CAF (3 mg), is more effective in improving short-term physical performance without affecting CAF side effects in female athletes. Nevertheless, when ingested in the evening, neither dose was sufficient to enhance short-term physical performance, and both dosages increased the incidence of CAF side effects, particularly at a moderate dose.
摘要：
虽然以前的研究已经探索了一系列影响运动员最佳使用咖啡因（CAF）的因素，有限的研究已经探索了一天中的时间（TOD）如何影响各种CAF剂量对身体表现的麦角效应。这项研究旨在增加有关推荐的CAF剂量（3mg/kg与在不同的TOD下摄入6mg/kg）会影响女运动员的最大高强度身体表现和潜在副作用的感知。在这个双盲中，随机化，和平衡研究，15名低CAF消费者运动员(年龄18.3±0.5岁)接受了6次试验，包括在两个TOD中评估的三个测试条件：一个在早上（上午08:00）和一个在晚上（下午06:00）。在每种情况下，参与者摄入了安慰剂，3mg/kgCAF（CAF（3mg）），或6mg/kgCAF（CAF（6mg））胶囊在每次测试前60分钟，中间冲洗时间至少为72小时。在每次试验中，参与者进行了反运动跳跃测试(CMJ)，改进的敏捷性t检验(MATT)，重复冲刺能力(RSA)，感知劳累(RPE)评级，最后，CAF副作用问卷。我们的发现表明对CMJ没有体格效应，MAT,与安慰剂相比，施用CAF（3mg）或CAF（6mg）后晚上的RSA表现。同样，当早上摄入CAF时，CAF（3mg）和CAF（6mg）的这些性能均有所改善，CAF（6mg）后观察到更大的改善。此外,CAF剂量和TOD对RPE均无显著影响。晚上摄入CAF后，副作用的发生率显着增加，特别是中等剂量的CAF（6毫克）。我们的发现表明，CAF的有效性取决于TOD和CAF剂量。当早上摄入时，中等剂量的CAF（6毫克），而不是CAF（3毫克），在不影响女运动员CAF副作用的情况下更有效地改善短期身体表现。然而，在晚上摄入时，两种剂量都不足以增强短期身体机能，两种剂量都增加了CAF副作用的发生率，特别是在中等剂量。
