PURPOSE Although caffeine is known to possess ergogenic effects, previous studies demonstrated no effect of caffeine on 800-m run performance outdoors which might be due to several uncontrolled factors including pacing strategies. We hypothesized that caffeine ingestion improves a pace-controlled simulated 800-m run performance. We also hypothesized that exercise-induced arterial hypoxemia (EIAH) occurs during the simulated 800-m run, and this response is mitigated by caffeine-induced increases in exercise ventilation. METHODS In a randomized, double-blind, placebo-controlled and crossover design, sixteen (3 females) college middle-distance runners who have 800-m seasonal best of 119.97 ± 7.64 s ingested either 1) placebo (6 mg of glucose/kg of body weight) or caffeine (6 mg of caffeine/kg of body weight). Then they performed an 800-m run consisting of 30-s running at 103% of their 800-m seasonal best, followed by running at 98% of seasonal best until exhaustion, which mimics actual 800-m run pacing pattern. RESULTS Running time to exhaustion was extended by 7.3 ± 6.2% in the caffeine-ingested relative to placebo trial (123 ± 12 vs. 114 ± 9 s, P = 0.04). Arterial oxygen saturation markedly decreased during the simulating running, but this response was similar (76.6 ± 5.7 vs. 81.1 ± 5.2%, at 113 s) between the caffeine vs. placebo trials (P ≥ 0.23 for time×supplement interaction and main effect of supplement). Minute ventilation, oxygen uptake (all P ≥ 0.36 for time×supplement interaction and main effect of supplement) and rate of perceived exertion (all P ≥ 0.11) did not differ between the trials throughout the simulating running. HR was higher in the caffeine-ingested trial throughout the simulated running (P < 0.01 for main effect of supplement). Postexercise blood lactate concentration was higher in the caffeine trial (P = 0.02). CONCLUSIONS Caffeine ingestion improves simulated 800-m run performance without affecting exercise ventilation and severe EIAH.

中文翻译：

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咖啡因可提高模拟 800 米跑步表现，而不影响严重运动引起的动脉低氧血症。

目的虽然众所周知咖啡因具有增效作用，但之前的研究表明咖啡因对户​​外 800 米跑步表现没有影响，这可能是由于包括配速策略在内的几个不受控制的因素造成的。我们假设摄入咖啡因可以改善配速控制的模拟 800 米跑步表现。我们还假设，在模拟 800 米跑步过程中会发生运动引起的动脉低氧血症 (EIAH)，并且咖啡因引起的运动通气量增加可以减轻这种反应。方法 在随机、双盲、安慰剂对照和交叉设计中，16 名（3 名女性）大学中长跑运动员的 800 米季节性最佳成绩为 119.97 ± 7.64 秒，摄入 1) 安慰剂（6 毫克葡萄糖/公斤）体重）或咖啡因（6 毫克咖啡因/公斤体重）。然后，他们进行了 800 米跑步，其中包括以 800 米季节性最佳成绩的 103% 跑 30 秒，然后以季节性最佳成绩的 98% 跑步直至精疲力尽，这模仿了实际的 800 米跑步配速模式。结果 相对于安慰剂试验，摄入咖啡因的跑步至力竭的时间延长了 7.3 ± 6.2%（123 ± 12 秒 vs. 114 ± 9 秒，P = 0.04）。模拟跑步期间动脉血氧饱和度显着下降，但咖啡因试验与安慰剂试验之间的反应相似（113 秒时为 76.6 ± 5.7 与 81.1 ± 5.2%）（时间×补充剂相互作用和主效应 P ≥ 0.23）补充）。在整个模拟跑步过程中，每分钟通气量、摄氧量（时间×补充剂相互作用和补充剂主效应的所有 P ≥ 0.36）和感知用力率（所有 P ≥ 0.11）在试验之间没有差异。在整个模拟跑步过程中，摄入咖啡因的试验中 HR 较高（补充剂的主效应 P < 0.01）。咖啡因试验中运动后血乳酸浓度较高（P = 0.02）。结论 摄入咖啡因可改善模拟 800 米跑步表现，而不影响运动通气和严重 EIAH。