Background Equivocal findings examining the influence of caffeine on performance and biological responses to exercise may be due to inter-individual variability in cardiorespiratory or neuromuscular fitness. This study examined whether the effects of caffeine ingestion on exercise performance and biological responses to prolonged intermittent exercise to exhaustion depend on cardiorespiratory or neuromuscular fitness. Methods Twenty male soccer players, separated according to either cardiorespiratory fitness (high vs medium) or neuromuscular fitness (high vs medium) underwent two trials simulating the cardiovascular demands of a soccer game to exhaustion on treadmill after ingesting either caffeine (6 mg∙kg − 1 ) or placebo. Physical performance, cardiorespiratory and metabolic parameters and blood metabolites were evaluated. Results Time to exhaustion (719 ± 288 vs 469 ± 228 s), jump height (42.7 ± 4.2 vs 38.6 ± 4.4 cm), heart rate (163 ± 12 vs 157 ± 13 b ∙ min − 1 ), mean arterial blood pressure (98 ± 8 vs 92 ± 10 mmHg), plasma glucose (5.6 ± 0.7 vs 5.3 ± 0.6 mmol∙l − 1 ) and lactate (3.3 ± 1.2 vs 2.9 ± 1.2 mmol∙l − 1 ) were higher, while rating of perceived exertion (12.6 ± 1.7 vs 13.3 ± 1.6) was lower with caffeine vs placebo ( p < 0.01), independent of cardiorespiratory or neuromuscular fitness level. Reaction time; plasma glycerol, non-esterified fatty acids and epinephrine; carbohydrate and fat oxidation rates; and energy expenditure were not affected by caffeine ( p > 0.05). Conclusions Caffeine was effective in improving endurance and neuromuscular performance in athletes with either high or medium cardiorespiratory and neuromuscular fitness. Cardiorespiratory and neuromuscular fitness do not appear to modulate the ergogenic effects of caffeine supplementation in well-trained athletes.

中文翻译：

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咖啡因补充剂对足球运动员具有致力作用，与心肺或神经肌肉健康水平无关

背景 检查咖啡因对运动表现和生物学反应的影响的模棱两可的发现可能是由于心肺或神经肌肉健康的个体差异。这项研究检查了摄入咖啡因对运动表现的影响以及对长时间间歇性运动导致疲惫的生物反应是否取决于心肺或神经肌肉健康。方法 20 名男性足球运动员，根据心肺适能（高 vs 中）或神经肌肉适能（高 vs 中）进行了两项试验，模拟足球比赛对心血管的需求，在摄入咖啡因（6 mg·kg - 1) 或安慰剂。评估了身体机能、心肺和代谢参数以及血液代谢物。结果 疲劳时间（719 ± 288 vs 469 ± 228 s）、跳跃高度（42.7 ± 4.2 vs 38.6 ± 4.4 cm）、心率（163 ± 12 vs 157 ± 13 b ∙ min − 1 ）、平均动脉血压（ 98 ± 8 vs 92 ± 10 mmHg)、血浆葡萄糖 (5.6 ± 0.7 vs 5.3 ± 0.6 mmol∙l − 1 ) 和乳酸 (3.3 ± 1.2 vs 2.9 ± 1.2 mmol∙l − 1 ) 更高，而感知到的劳累评分(12.6 ± 1.7 vs 13.3 ± 1.6) 咖啡因与安慰剂相比较低 (p < 0.01)，与心肺或神经肌肉健康水平无关。反应时间; 血浆甘油、非酯化脂肪酸和肾上腺素；碳水化合物和脂肪氧化率；和能量消耗不受咖啡因的影响（p > 0.05）。结论 咖啡因可有效提高具有高或中等心肺和神经肌肉健康的运动员的耐力和神经肌肉表现。