تاثیر مکمل یاری کوتاه مدت کافئین - آب چغندر بر تغییرات کاتکولامینها لاکتات و شاخص درک فشار به دنبال فعالیت شدید بی هوازی در دوندگان نخبه مرد.

Background & Aims: Athletes use variety of compounds to improve athletic performance and are constantly striving to improve capacity and performance. Various supplements are used by the masses and regularly by athletes in exercise to take advantage of the energizing properties as well as to prevent or delay fatigue (1). Dietary supplements, in addition to proper exercise and nutrition to improve athletic performance, are recognized, including caffeine and nitrate supplements. Since both beet juice and caffeine supplements are safe, effective, and legal, it seems that combining these two supplements and using them by athletes can have an increasing effect on improving athletic performance. Caffeine is used by many athletes as an ergogenic supplement, and low and moderate doses of caffeine (3 to 6 mg/kg) are very useful for a variety of exercise (2). Also, the use of beet juice supplementation in speed runners increased the concentration of lactate in the blood, while there was no difference in the amount of oxygen consumed (7). According to the results of other studies, it seems that the use of nitrate supplementation can reduce the time required to run 10 km and maintain lactate levels in the constant range. However, it seems that 30 days of nitrate supplementation combined with continuous aerobic exercise can improve the performance of running 10 km compared to running alone, one of the mechanisms for which is stability at the surface Blood lactate (8). The results of a study showed that the use of nitric oxide as supplement can accelerate the clearance of lactate from the body after exercise and thus accelerate recovery (9). In study of Bescós et al. (2011) two randomized blinds stated that the use of nitrate supplementation as a single dose of 10 mg per kg of body weight 3 hours before exercise had an effect on athletic performance and arrival time. Also, it did not cause fatigue and the use of this supplement and with this dose did not affect the heart rate (10). Belbis et al. (2018) examined the effect of 200 mg of caffeine on repetitive running activity on heart rate and lactate levels. The results of this study showed that caffeine supplementation at dose of 200 mg can increase performance in repetitive doses compared to counterparts in the control group (11). Due to the very limited studies of supplementation of caffeine and beet juice and the lack of comparison of doses used in professional runners with field protocol and considering the conditions of intense aerobic and anaerobic training subsequently and in a short time in most sports to Improves anaerobic power and lactate threshold, as well as strengthens cardiovascular endurance during training and tournaments that probably have more than one training session per day, and considering that running is used as one of the pillars of training to increase the performance of athletes by coaches., Therefore, the aim of this study was to investigate the effect of short-term caffeine-beet juice supplementation on catecholamine changes, lactate and Rating of Perceived Exertion following intense anaerobic activity in elite male runners. Methods: In this quasi-experimental study, 30 elite male runners (age 27.5±3.8 y, height: 176.7±7 cm, body fat: 9.9±1.7 %) were randomly divided into three exercise groups with 1) high dose supplement (9.6 mmol Beet extract and 400 mg caffeine), 2) low-dose supplement (4.8 mmol beet extract and 200 mg caffeine) and 3) placebo group (natural beet juice). total of 36 sessions were performed in three stages and two stages of six-day wash out between the first and second stages and the second and third stages. Levels of epinephrine and norepinephrine, lactate and pressure perception were measured. Data were analyzed using analysis of variance with repeated measures at the P<0.05. Results: The results showed that supplementation and exercise no significant changes in epinephrine levels (p = 0.93), norepinephrine (p = 0.89) and lactate (p = 0.37), but has had a significant effect on the perception of runner pressure (p<0.001). Also, supplementation and exercise caused significant changes in catecholamine levels (p<0.001). As the time elapsed after running, lactate levels decreased more than at baseline (p<0.001). Also, with increasing running distance, the rate of pressure perception increased (p<0.001). Conclusion: The results of the present study showed that short-term supplementation with beet juice and caffeine was not able to significantly change the levels of catecholamines, lactate in elite runners, but was significantly reduce the pressure perception. The findings of this study were consistent with the results of Previous research (14-19). It has been shown that nitrate supplements for 15 days can reduce the perception of pressure, increase oxygen saturation and also increase the time to reach fatigue (23). Nitrate is an organic ion found in many foods, especially vegetables such as celery, beets, lettuce and spinach (24, 25). Following consumption, nitrate enters the bloodstream and has a shelf life of about 5 hours. Once absorbed into the bloodstream, nitrate is converted to nitrite and then nitric oxide, which can dilate blood vessels, increase blood flow, reduce muscle energy expenditure, improve nutrient delivery to muscle, and increase calcium ion release, and ultimately Improve runners' performance (26,27). Short-term nitrate supplementation appears to increase nitric oxide bioavailability and inhibit sympathetic vasoconstriction in resting or contracting muscle, however, some studies have shown conflicting results. Nitrate supplementation has been shown to be unable to alter vascular contraction due to sympathetic effects in young male athletes (27). also, the physiological effects of caffeine supplementation are not well understood, but it appears that the effects of caffeine on heart rate are influenced by the intensity of exercise and caffeine supplementation can reduce heart rate and blood pressure perception (32). It seems that the lack of significance in high and low doses of caffeine and beet juice supplementation on catecholamine variables indicates the lack of sympathetic effect of this combined supplement or that the presence of caffeine and nitrate together can neutralize each other. In relation to the exercise pressure perception index, the difference in the dose received by this combined supplement had a significant effect, which indicates that by increasing the amount, the pain perception threshold can be increased. Possible mechanisms include vasodilation, increased blood flow, improved delivery of nutrients and oxygen to the muscle, and increased calcium ion release and reduced fatigue. One of the limitations of this study is the lack of precise control of subjects in terms of food intake between the second to seventh day and also in the rest period between each stage. It also seems that individual differences in athletes' eating habits and body reactions may affect the response to variables due to the short duration of the intervention, especially in the case of caffeine, which despite the relative control during the study but the body Athletes show different responses to it, or the duration of the research is limited due to the professionalism of the athletes and the time that coaches allow them to participate in applied research. One of the strengths of this research is the use of supplements that are extracted from natural and daily foods. It is suggested that in future research on the recommended amounts of supplements with several different doses or in combination with other ergogenic supplements, preferably with a nutritional nature and not chemical and with a synergistic effect similar to this study and with longer use or in non-professionals. As well as other sports with the nature of endurance, strength or speed and skill to be considered. The results of this study showed that short-term supplementation with caffeine and beetroot juice as a source of nitrate did not cause significant changes in catecholamine, lactate and heart rate, but caused significant changes in runners' perception of pressure. Further studies are also needed to investigate possible mechanisms involved in athletes' anaerobic performance and more effective doses. It does not seem to combine these two supplements with each other or in higher doses compared to smaller amounts. [ABSTRACT FROM AUTHOR]