Zahedan J Res Med Sci. 2019 January; 21(1):e86250. Published online 2019 February 4. doi: 10.5812/zjrms.86250. Research Article Investigation of Six-Week Beetroot Juice Ingestion on VO 2 max in Female Soccer Players Maryam Lotfi 1 , Mohammad Azizi 1, * , Worya Tahmasebi 1 and Parviz Bashiri 2 1 Department of Exercise Physiology, Faculty of Sport Sciences, Razi University, Kermanshah, Iran 2 Department of Animal Science, Faculty of Animal Science, Razi University, Kermanshah, Iran * Corresponding author: Assistant Professor of Exercise Physiology, Department of Exercise Physiology, Faculty of Sport Sciences, Razi University, Kermanshah, Iran. Email: azizimihammad@gmail.com Received 2018 November 10; Revised 2019 January 06; Accepted 2019 January 26. Abstract Background: One of the beverages improving athletic performance is beetroot juice. Objectives: The aim of the present study was to investigate if six weeks of beetroot juice ingestion can increase VO2 max and improve the performance of female soccer players. Methods: 20 female soccer players (age: 23.13 ± 0.77 years) were selected and assigned into two groups: experimental (beetroot juice, n = 10) and control (placebo, n = 10). The Bruce test was first done to assess VO2 max without drinking beetroot juice. Then, the experimental group started consuming 200 mL of the juice two hours before each training session for six weeks. Finally, the second Bruce test was performed after six weeks of beetroot juice ingestion. Results: There was a significant increase in VO2 max in the experimental and control groups from pretest to posttest (P < 0.001). In addition, the results of independent samples t-test showed there was a significant difference between the experimental and control groups in VO2 max (P < 0.001, t = 12.39). Conclusions: The present study provides evidence that beetroot juice positively affects performance and increases the maximum volume of oxygen consumption in female soccer players. Therefore, we can propose this juice to female soccer players to improve their performance. Keywords: Soccer, Beetroot Juice, VO2 max, Performance 1. Background Soccer is a strength and power-contact sport that in- cludes high-intensity activity, training, and competition (1). Physiological, technical, and tactical skills are impor- tant for soccer performance. Factors such as acceleration, speed, jump height, and energy release capacity are of most importance in soccer. Due to the duration of a soc- cer match, 90% of the energy release is aerobic. The aero- bic endurance performance in soccer depends on three fac- tors: maximal oxygen consumption (VO 2 max), anaerobic threshold, and work economy (2). It is known that the dis- tance covered in high intensity and speed is more in men than in women (3), which is due to the low VO 2 max and the anaerobic power of female soccer players (4). Athletic performance is one of the issues to which soccer players at- tend. They use various supplementations to increase their performance. Although supplements may temporarily im- prove their athletic performance, their long-term use will increase the damage to the blood, kidneys, and liver. A no- table factor of performance is the maximal oxygen uptake (VO 2 max). VO 2 max measures the maximum amount of oxygen consumed by the body per minute that is typically expressed in mL/kg/min. The higher the VO 2 max value pro- duced by an individual, the greater the rate of oxygen con- sumption by the athlete’s body and the higher the level of fitness. Minor increases in VO 2 max can have remark- able advantages, especially in team sports. For example, some researchers speculate that if every player in a soc- cer team has a VO 2 max of just 6 mL/kg/min higher than the opponent has, the aerobic capability possessed would equate essentially having an additional player in the field (5). VO 2 max can be increased in an individual over time by participating in different types of endurance training pro- grams (6). The advantage of a higher VO 2 max is that there is a greater delivery of oxygen from the blood to the mus- cle tissues, so athletes may work at a higher intensity for a longer time. Increased blood flow is attributed mostly to increased cardiac output, but also to the muscle pump and local mediation of vasodilation near the muscle tissue. Copyright © 2019, Zahedan Journal of Research in Medical Sciences. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License (http://creativecommons.org/licenses/by-nc/4.0/) which permits copy and redistribute the material just in noncommercial usages, provided the original work is properly cited.