Wang Lijun, Zhao Ruohan, Yan Yuhang, Zhang Hongli, Yan Ruixin, Zhu Yifan, Han Zhuohong, Qu Yue, Wang Ruonan, Li Yicheng, Chao Ruolin
Institute of Physical Education, Shaanxi Normal University, Xi'an, China.
Municipal Environmental Engineering Institute, Xian University of Architecture and Technology, Xi'an, China.
Front Nutr. 2025 May 8;12:1576712. doi: 10.3389/fnut.2025.1576712. eCollection 2025.
In bodybuilding competitions, athletes are required to hold static poses for extended periods. This study aimed to evaluate the effects of acute beetroot juice (BJ) supplementation on isometric muscle endurance in college bodybuilding athletes.
Sixteen male college bodybuilding athletes participated in a randomized, double-blind, crossover study conducted over three weeks with four laboratory visits. The first visit involved explaining the experimental protocol and performing the maximal voluntary isometric contraction (MVIC) test. The second visit familiarized participants with the testing procedures. During subsequent visits, participants consumed either BJ (250 ml,∼ 12.48 mmol of NO3-) or PL (250 ml,∼ 0.0005 mmol of NO3-), and blood samples were collected before testing to measure nitrate (NO3-) and nitrite (NO2-) concentrations. Participants then performed three rounds of isometric circuit endurance tests (ICET), during which heart rate (HR), ratings of perceived exertion (RPE), and blood lactate levels were recorded. Each round of ICET consisted of four subtests targeting the elbow flexors, core muscles, forearm muscles, and knee extensors, maintaining 70% of MVIC until fatigue. Additionally, surface electromyography (sEMG) was used to record and analyze muscle activity.
Compared to PL, acute BJ supplementation resulted in a 10.87-fold and 1.57-fold increase in serum NO3- and NO2- levels, respectively ( < 0.001). No significant differences were observed in MVIC peak torque under different conditions ( > 0.05). In the third round of testing (ICET-3), endurance improved by 14.9, 25.4, and 25.2% for the elbow flexors, forearm muscles, and knee extensors, respectively. No significant differences in root mean square (RMS) values were observed between the BJ and PL groups ( > 0.05).
These data suggest that acute beetroot juice supplementation had no significant effect on MVIC in college bodybuilding athletes but improved endurance in certain muscle groups during ICET. This suggests that nitrates may enhance endurance by optimizing intermittent recovery processes rather than directly increasing strength.
在健美比赛中，运动员需要长时间保持静态姿势。本研究旨在评估急性补充甜菜根汁（BJ）对大学生健美运动员等长肌肉耐力的影响。
16名男性大学生健美运动员参与了一项为期三周、进行四次实验室访问的随机、双盲、交叉研究。第一次访问包括解释实验方案并进行最大自主等长收缩（MVIC）测试。第二次访问让参与者熟悉测试程序。在随后的访问中，参与者饮用BJ（250毫升，约12.48毫摩尔硝酸盐）或安慰剂（PL，250毫升，约0.0005毫摩尔硝酸盐），并在测试前采集血样以测量硝酸盐（NO3-）和亚硝酸盐（NO2-）浓度。参与者随后进行三轮等长循环耐力测试（ICET），在此期间记录心率（HR）、主观用力程度（RPE）和血乳酸水平。每轮ICET由针对肘屈肌、核心肌肉、前臂肌肉和膝伸肌的四个子测试组成，保持MVIC的70%直至疲劳。此外，使用表面肌电图（sEMG）记录和分析肌肉活动。
与PL相比，急性补充BJ导致血清NO3-和NO2-水平分别增加10.87倍和1.57倍（<0.001）。在不同条件下，MVIC峰值扭矩未观察到显著差异（>0.05）。在第三轮测试（ICET-3）中，肘屈肌、前臂肌肉和膝伸肌的耐力分别提高了14.9%、25.4%和25.2%。BJ组和PL组之间的均方根（RMS）值未观察到显著差异（>0.05）。
这些数据表明，急性补充甜菜根汁对大学生健美运动员的MVIC没有显著影响，但在ICET期间提高了某些肌肉群的耐力。这表明硝酸盐可能通过优化间歇性恢复过程而不是直接增加力量来提高耐力。
