1Department of Physical Performance, Norwegian School of Sport Sciences, Ullevål Stadion, Oslo, NORWAY; and 2Department of Chemical and Biological Working Environment, National Institute of Occupational Health, Oslo, NORWAY.
Med Sci Sports Exerc. 2014 Sep;46(9):1787-96. doi: 10.1249/MSS.0000000000000288.
Performance improvements after caffeine (CAF) ingestion are well documented when using a 1-d protocol. In numerous competitions such as the Tour de France, Tour de Ski, world championships, and National College Athletic Association championships, athletes compete for several days in a row. To date, no studies have investigated the effects of CAF when competing for consecutive days in a row. This study aimed to investigate the effects of placebo (PLA) and two different CAF doses (3 and 4.5 mg·kg body mass) on performance in a 10-min all-out, cross-country, double poling ergometer test (C-PT) 2 d in a row.
Eight highly trained male cross-country skiers (V˙O2max-run, 78.5 ± 1.6 mL·kg·min) participated in the study, which was a randomized, double-blind, PLA-controlled, crossover design. Performance was assessed as distance covered during a 10-min all-out C-PT. Oral ingestion of CAF or PLA was consumed 75 min before the all-out C-PT.
Poling distance was improved after CAF ingestions compared with that after PLA on both days. The improvements on day 1 were 4.0% (90% confidence limits, ±3.3) and 4.0% ± 2.9% for both CAF doses, respectively (P < 0.05), whereas improvements on day 2 were 5.0% ± 3.6% and 5.1% ± 2.8% for CAF3 and CAF4.5, respectively, compared with those for PLA. Improved performance was associated with increased HR, adrenaline concentration, blood lactate concentration, and V˙O2 consumption after CAF ingestion. Furthermore, performance was elevated despite higher creatine kinase concentration and muscular pain at arrival on day 2 for both CAF doses.
Both CAF doses improved performance in the 10-min all-out C-PT compared with PLA over two consecutive days. Therefore, CAF seems useful for athletes competing over consecutive days despite higher muscle damage occurring after enhanced performance on the first day.
在使用 1 天方案时，咖啡因（CAF）摄入后性能提高已得到充分记录。在许多比赛中，如环法自行车赛、冬季两项世界杯、世界锦标赛和全国大学生体育协会锦标赛，运动员连续几天比赛。迄今为止，尚无研究调查 CAF 在连续多天比赛时的影响。本研究旨在调查安慰剂（PLA）和两种不同 CAF 剂量（3 和 4.5 mg·kg 体重）对连续 2 天进行 10 分钟全力、越野、双杆测功计测试（C-PT）的性能影响。
8 名受过高度训练的男性越野滑雪运动员（V˙O2max 跑步，78.5 ± 1.6 mL·kg·min）参加了这项随机、双盲、PLA 对照、交叉设计的研究。性能评估为 10 分钟全力 C-PT 期间覆盖的距离。在全力 C-PT 前 75 分钟口服 CAF 或 PLA。
与 PLA 相比，CAF 摄入后两天的 pole 距离都有所提高。第 1 天的改善分别为 4.0%（90%置信区间，±3.3）和 CAF 两种剂量的 4.0%±2.9%（P<0.05），而第 2 天的改善分别为 CAF3 和 CAF4.5 的 5.0%±3.6%和 5.1%±2.8%，与 PLA 相比。在 CAF 摄入后，HR、肾上腺素浓度、血乳酸浓度和 V˙O2 消耗增加，与性能提高相关。此外，尽管 CAF 两种剂量在第 2 天到达时肌酸激酶浓度和肌肉疼痛升高，但仍能提高性能。
与 PLA 相比，CAF 两种剂量在连续 2 天的 10 分钟全力 C-PT 中均提高了性能。因此，尽管在第 1 天表现增强后发生更高的肌肉损伤，但 CAF 似乎对连续多天比赛的运动员有用。
