Shaw Keely, Singh Jyotpal, Sirant Luke, Neary J Patrick, Chilibeck Philip D
University of Saskatchewan.
University of Regina.
Int J Sport Nutr Exerc Metab. 2020 Sep 11;30(6):420-426. doi: 10.1123/ijsnem.2020-0051. Print 2020 Nov 1.
Dark chocolate (DC) is high in flavonoids and has been shown to increase nitric oxide in the blood. Increased nitric oxide has the potential to improve delivery of oxygen to muscle, especially in hypoxic conditions, such as altitude. Our aim was to assess the impact of DC supplementation on cycling performance at altitude. Twelve healthy, trained cyclists (n = 2 females, n = 10 males; age = 35 [12] years; height = 177 [7] cm; mass = 75.2 [11.0] kg; VO2max = 55 [6] ml·kg-1·min-1) were randomized to supplement with 60 g of DC or placebo twice per day for 14 days in a double-blind crossover study. After the 2 weeks of supplementation, the participants attended a laboratory session in which they consumed 120 g of DC or placebo and then cycled for 90 min at 50% peak power output, followed immediately by a 10-km time trial (TT) at simulated altitude (15% O2). The plasma concentration of blood glucose and lactate were measured before and at 15, 30, 60, and 90 min during the steady-state exercise and post TT, while muscular and prefrontal cortex oxygenation was measured continuously throughout exercise using near-infrared spectroscopy. DC resulted in a higher concentration of blood glucose (5.5 [0.5] vs. 5.3 [0.9] mmol/L) throughout the trial and lower blood lactate concentration following the TT (7.7 [1.92] vs. 10.0 [4.6] mmol/L) compared with the placebo. DC had no effect on the TT performance (19.04 [2.16] vs. 19.21 ± 1.96 min) or oxygenation status in either the prefrontal cortex or muscle. The authors conclude that, although it provided some metabolic benefit, DC is not effective as an ergogenic aid during TT cycling at simulated altitude.
黑巧克力（DC）富含类黄酮，且已被证明可增加血液中的一氧化氮。一氧化氮的增加有可能改善氧气向肌肉的输送，尤其是在低氧条件下，如在高海拔地区。我们的目的是评估补充DC对高海拔地区骑行表现的影响。在一项双盲交叉研究中，12名健康的、经过训练的自行车运动员（n = 2名女性，n = 10名男性；年龄 = 35 [12]岁；身高 = 177 [7]厘米；体重 = 75.2 [11.0]千克；最大摄氧量 = 55 [6]毫升·千克⁻¹·分钟⁻¹）被随机分配，每天两次补充60克DC或安慰剂，持续14天。在补充2周后，参与者参加了一次实验室测试，他们食用120克DC或安慰剂，然后以50%的峰值功率输出骑行90分钟，随后立即在模拟海拔（15%氧气）下进行10公里计时赛（TT）。在稳态运动期间以及TT后，分别在15、30、60和90分钟时以及运动前测量血糖和乳酸的血浆浓度，同时在整个运动过程中使用近红外光谱法连续测量肌肉和前额叶皮层的氧合情况。与安慰剂相比，DC在整个试验过程中导致血糖浓度更高（5.5 [0.5] 对5.3 [0.9]毫摩尔/升），并且在TT后血乳酸浓度更低（7.7 [1.92] 对10.0 [4.6]毫摩尔/升）。DC对TT表现（19.04 [2.16] 对19.21 ± 1.96分钟）或前额叶皮层或肌肉中的氧合状态没有影响。作者得出结论，尽管DC提供了一些代谢益处，但在模拟海拔的TT骑行中，它作为一种提高运动能力的辅助手段并不有效。
