Exercise Physiology Laboratory, Camilo José Cela University, Madrid, Spain.
Department of Physiology, EFFECTS-262 Research Group, Faculty of Medicine, University of Granada, Granada, Spain.
Eur J Nutr. 2022 Sep;61(6):3285-3292. doi: 10.1007/s00394-022-02894-z. Epub 2022 May 3.
Oral caffeine intake has been deemed as an effective supplementation strategy to enhance fat oxidation during aerobic exercise with a steady-state intensity. However, in real exercise scenarios, individuals habitually train with autoregulation of exercise intensity. This study aimed to analyze the effect of oral caffeine intake during self-paced cycling on autoregulated exercise intensity and substrate oxidation.
Fifteen young and healthy participants (11 men and 4 women) participated in a double-blind, randomized, cross-over investigation. Each participant took part in 2 experimental days consisting of pedaling for 1 h with a self-selected wattage. Participants were told that they had to exercise at a moderate intensity to maximize fat oxidation. On one occasion participants ingested 3 mg/kg of caffeine and on the other occasion ingested a placebo. Energy expenditure, fat oxidation rate, and carbohydrate oxidation rate were continuously measured during exercise by indirect calorimetry.
In comparison to the placebo, caffeine intake increased the self-selected wattage (on average, 105 ± 44 vs 117 ± 45 W, respectively, P < 0.001) which represented a higher total work during the cycling session (377 ± 157 vs 422 ± 160 kJ, P < 0.001). Caffeine increased total energy expenditure (543 ± 161 vs 587 ± 155 kcal, P = 0.042) but it did not affect total fat oxidation (24.7 ± 12.2 vs 22.9 ± 11.5 g, P = 0.509) or total carbohydrate oxidation (87.4 ± 22.4 vs 97.8 ± 32.3 g, P = 0.101).
Acute caffeine ingestion before an exercise session with an individual's freedom to regulate intensity induces a higher self-selected exercise intensity and total work. The selection of a higher exercise intensity augments total energy expenditure but eliminates the effect of caffeine on substrate oxidation during exercise.
口服咖啡因已被认为是一种有效的补充策略，可以在稳态强度的有氧运动中增强脂肪氧化。然而，在实际运动场景中，个体通常会通过自我调节运动强度来进行训练。本研究旨在分析口服咖啡因对自主调节运动强度和底物氧化的影响。
15 名年轻健康的参与者（11 名男性和 4 名女性）参与了双盲、随机、交叉研究。每位参与者参加了 2 天的实验，包括以自我选择的瓦特数蹬车 1 小时。告知参与者他们必须以中等强度运动，以最大限度地增加脂肪氧化。在一种情况下，参与者摄入 3mg/kg 的咖啡因，而在另一种情况下摄入安慰剂。通过间接测热法在运动过程中连续测量能量消耗、脂肪氧化率和碳水化合物氧化率。
与安慰剂相比，咖啡因摄入增加了自我选择的瓦特数（平均分别为 105±44 与 117±45 W，P<0.001），这代表在骑车过程中完成了更高的总工作量（377±157 与 422±160 kJ，P<0.001）。咖啡因增加了总能量消耗（543±161 与 587±155 kcal，P=0.042），但不影响总脂肪氧化（24.7±12.2 与 22.9±11.5 g，P=0.509）或总碳水化合物氧化（87.4±22.4 与 97.8±32.3 g，P=0.101）。
在个体自由调节强度的运动前摄入急性咖啡因会导致更高的自我选择运动强度和总工作量。选择更高的运动强度会增加总能量消耗，但消除了咖啡因对运动中底物氧化的影响。
