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Study aim: the purpose of this study was to assess the effect of 3 mg and 5 mg per kg of body weight of caffeine on heart rate, blood pressure and shooting performance among elite shooters. Material and methods: sStudy participants comprised 8 male shooters among athletes at the national level with at least 2 years of experience, with the mean age (26.50±13.08 years), weight (73.02 ± 12.2 kg), height (174.62 ± 8.97 cm) and BMI (23.93 ± 2.88 kg/m2). The blood pressure and heart rate of all participants were measured at rest. Participants then randomly took caffeine (3 mg and 5 mg per kg of body weight) or placebo for 3 different days, 2 days apart. One hour after ingestion, they shot with rifle and air pistol. Statistical analysis was performed using the ANOVA with repeated measures and the Bonferroni test. Results: the results of the survey showed that taking 5 mg/kg of caffeine caused a significant increase in systolic blood pressure (p < 0.001), diastolic blood pressure (p < 0.05) and also caused a significant increase in heart rate (p < 0.05) and a significant decrease in shooting performance (p < 0.05). Moreover, taking 3 mg/kg of caffeine caused a significant increase in systolic blood pressure (p < 0.05). But this amount of caffeine had no significant effect on the heart rate, diastolic blood pressure or shooting performance (p < 0.05). Conclusions: the results of this study suggest that taking 5 mg/kg of caffeine can increase the blood pressure and heart rate of the shooters that leads to a decrease in shooting performance.
Study aim: To compare the effects of caffeine on metabolic and cardiovascular responses to exercise in lean and obese subjects.Material and methods: In a double blind random design, 6 lean (BMI<20) and 6 obese (BMI>28) sedentary young men performed treadmill running for 30 min at similar exercise intensities (60% VO2max) one hour after caffeine (5 mg/kg body mass) or placebo ingestion. Gas exchange was measured by indirect calorimetry/open-circuit spirometry. Heart rate (HR) was measured throughout the exercise. Blood pressure (BP) measurements were taken at baseline, 1 h after caffeine/placebo ingestion and immediately after exercise. Repeated measures ANOVA was used in data analysis.Results: Caffeine significantly (p<0.05 - 0.01) increased the exercise-induced oxygen uptake, energy expenditure, systolic blood pressure and heart rate in both groups, the respiratory exchange ratio remaining unchanged. The effects of caffeine were in both groups alike.Conclusions: Caffeine activates metabolism without inducing major changes in fat/carbohydrate oxidation. The differences in body fat content seem not to affect the caffeine-induced effects in a submaximal exercise.
Caffeine is a natural plant product found in many drinks, including coffee, tea, soft and energy drinks. Due to caffeine’s presence in the environment, microorganisms have evolved two different mechanisms to live on caffeine. The genetic maps of the caffeine N-demethylation pathway and C-8 oxidation pathway have been discovered in Pseudomonas putida CBB5 and Pseudomonas sp. CBB1, respectively. These genes are the only characterized bacterial caffeine-degrading genes, and may be of great value in producing fine chemicals, biofuels, and animal feed from coffee and tea waste. Here, we present preliminary results for production of theobromine and 7-methylxanthine from caffeine and theobromine, respectively, by two strains of metabolically engineered E. coli. We also demonstrate complete decaffeination of tea extract by an immobilized mixed culture of Klebsiella and Rhodococcus cells. These processes provide a first level demonstration of biotechnological utilization of coffee and tea waste.
Content available remote Coffee consumption and risk of stroke: a meta-analysis of cohort studies
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