Institute of Sport Sciences, The Jerzy Kukuczka Academy of Physical Education in Katowice, 40-065 Katowice, Poland.
Faculty of Physical Education, Gdansk University of Physical Education and Sport, 80-336 Gdansk, Poland.
Nutrients. 2020 Dec 13;12(12):3813. doi: 10.3390/nu12123813.
By using deceptive experimental designs, several investigations have observed that trained individuals may increase their performance when told they were given caffeine, when in fact they received a placebo (i.e., the placebo effect of caffeine). However, most of these investigations on the placebo effect of caffeine used individuals with low caffeine consumption or did not report habitual caffeine consumption, especially in studies analyzing resistance-based exercise. Hence, it is unknown if habitual caffeine consumers benefit from the placebo effect of caffeine on exercise performance. Thus, the aim of the present study was to analyze the placebo effect of caffeine on maximal strength and strength-endurance performance during the bench press exercise (BP) in women with mild-moderate daily consumption of caffeine.
Thirteen resistance-trained women (BP one-repetition maximum (1RM) = 40.0 ± 9.7 kg) habituated to caffeine (4.1 ± 1.7 mg/kg/day) completed a deceptive randomized experimental design with two experimental trials. On one occasion, participants were told that they would receive 6 mg/kg of caffeine but received a placebo (PLAC), and on other occasions, participants did not receive any substance and were told that this was a control situation (CONT). In each experimental trial, participants underwent a 1RM BP test and a strength-endurance test consisting of performing the maximal number of repetitions at 50% of their 1RM.
In comparison to CONT, PLAC did not enhance 1RM (40.0 ± 10.5 kg vs. 41.0 ± 9.5 kg, respectively; = 0.10), nor did it enhance the number of repetitions (32.2 ± 5.1 vs. 31.8 ± 4.5; = 0.66) or mean power (130 ± 34 vs. 121 ± 26; = 0.08) in the strength-endurance test.
Informing participants that they were given caffeine, when in fact they received a placebo, did not modify any performance variable measured in this investigation. Thus, the use of the placebo effect of caffeine seemed an ineffective strategy to enhance muscle strength and strength endurance during the BP exercise in women with mild-moderate consumption of caffeine.
通过使用欺骗性的实验设计，多项研究观察到，当告知训练有素的个体他们摄入了咖啡因时，即使实际上他们摄入的是安慰剂（即咖啡因的安慰剂效应），他们的表现可能会提高。然而，大多数关于咖啡因安慰剂效应的研究都使用了低咖啡因摄入的个体，或者没有报告习惯性咖啡因摄入，尤其是在分析基于阻力的运动的研究中。因此，尚不清楚习惯性咖啡因消费者是否受益于咖啡因对运动表现的安慰剂效应。因此，本研究的目的是分析在习惯性摄入低剂量咖啡因的女性中，咖啡因的安慰剂效应是否会对卧推运动（BP）的最大力量和力量耐力表现产生影响。
13 名接受过阻力训练的女性（BP 一次重复最大重量（1RM）= 40.0 ± 9.7 公斤）习惯于每天摄入 4.1 ± 1.7 毫克/公斤的咖啡因，完成了一项具有欺骗性的随机实验设计，共进行了两次实验。在一次实验中，参与者被告知他们将摄入 6 毫克/公斤的咖啡因，但实际上他们摄入了安慰剂（PLAC），而在另一次实验中，参与者没有摄入任何物质，并被告知这是一种对照情况（CONT）。在每次实验中，参与者都进行了 1RM BP 测试和力量耐力测试，包括以 1RM 的 50%最大重复次数进行测试。
与 CONT 相比，PLAC 并没有提高 1RM（40.0 ± 10.5 公斤与 41.0 ± 9.5 公斤相比； = 0.10），也没有提高重复次数（32.2 ± 5.1 次与 31.8 ± 4.5 次相比； = 0.66）或力量耐力测试中的平均功率（130 ± 34 瓦与 121 ± 26 瓦相比； = 0.08）。
告知参与者他们摄入了咖啡因，而实际上他们摄入了安慰剂，并没有改变本研究中测量的任何表现变量。因此，在习惯性摄入低剂量咖啡因的女性中，使用咖啡因的安慰剂效应似乎是一种无效的策略，无法增强卧推运动中的肌肉力量和力量耐力。
