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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.
EN
Study aim: the aim of this study was to compare the accuracy of a contactless photoplethysmographic mobile application (CPA) to record post-exercise heart rate and estimate maximal aerobic capacity after the Queen’s College Step Test. It was hypothesised that the CPA may present a cost effective heart rate measurement tool for educators and practitioners with limited access to specialised laboratory equipment. Materials and Methods: seventeen participants (eleven males and six females, 28 ± 9 years, 75.5 ± 15.5 kg, 173.6 ± 9.8 cm) had their heart rate measured immediately after the 3-min test simultaneously using the CPA, a wireless heart rate monitor (HRM) and manually via palpation of the radial artery (MAN). Results: both the CPA and MAN measurements had high variance compared to the HRM (CV = 31 and 11% respectively, ES = 1.79 and 0.65 respectively), and there were no significant correlations between the methods. Maximal oxygen consumption was estimated 17% higher in CPA compared to HRM (p < 0.001). Conclusions: in conclusion it is recommended that field practitioners should exercise caution and assess the accuracy of new freely available technologies if they are to be used in practice.
EN
Generally, it is assumed that heart-rhythm disorders during hypoxia result from the interplay between the autonomic nervous system (ANS) and the direct effect of hypoxia on cardiorespiratory structures of the central nervous system and on the myocardium. Circadian variability in the ANS may substantially influence the electrical stability of the myocardium, and thus it is associated with the preconditioning protective mechanism. We designed our study using anaesthetized Wistar rats (ketamine/xylazine 100 mg/15 mg/kg, i.m., open chest experiments) to evaluate the effect of preconditioning (PC) induced by 1 to 3 cycles (1 PC–3 PC) of asphyxia (5 min. of artificial hypoventilation, VT = 0.5 ml/100 g of b.w., 20 breaths/min.) and reoxygenation (5 min. of artificial ventilation, VT = 1 ml/100 g of b.w., 50 breaths/min.) on the heart rate (HR) during followed exposure 20 minutes of hypoventilation after adaptation to a light-dark (LD) cycle of 12 hours:12 hours. Hypoxic HR increases were only minimally prevented by 1 to 2 PC pre-treatment, particularly during the dark part of the day. A statistically significant HR increase required 3 PC and was seen only in the light part of the day. We concluded that possible ANS participation in asphyxic preconditioning depends not only on the number of preconditioned cycles but also on the LD cycle, when the ANS participation in preconditioning can be effective only in the light (nonactive) period.
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EN
The aim of study was to analyze heart rate variability (HRV) after different cardiac valve surgery procedures and the prognostic values of these findings. This study included 101 consecutive patients who underwent surgical implantation for an artificial valve. The mean age of the patients was 62 ± 10 years. An aortic valve was implanted in 65 patients. A mitral valve was implanted in 36 patients. HRV was analyzed from 24 hours Holter electrocardiographic (ECG) records. The time from the operation to the recording of Holter ECG and measuring HRV was 3.8 ± 1.4 months. After discharged from stationary cardiac rehabilitation, all involved patients were contacted to provide data on their health in the follow-up period (33 ± 21 months). A total of 46 patients with an implanted artificial valve had decreased overall HRV or standard deviation of all normal R-R intervals (SDNN) < 93 ms. Patients with an implanted artificial mitral valve had a shorter RR interval (817 ± 122 vs. 863 ± 122ms, p=0.03) and lower values of total power (1166 ± 1888 vs. 2802 ± 3601 ms2, p<0.001) compared to patients with an implanted artificial aortic valve. The results of study show that several months after cardiac surgery, almost half of the patients with an implanted artificial valve have decreased HRV. However, postoperative decreased HRV in those patients have no importance in long-term prediction of mortality rate.
EN
Study aim: To compare the effects of 6-week isokinetic and isotonic training programmes on heart rate and blood pressure in high school students.Material and methods: Twenty-nine healthy, untrained male student subjects aged 15 - 18 years participated in the study. They were assigned into 3 groups: control (C; n = 11), and subjected to isokinetic (IK; n = 8) or isotonic (IT; n = 10) training lasting 6 weeks, 3 days a week. Isokinetic exercises consisted of 3 sets of 20-s extensions/flexions (both knees) at 180°/s, spaced by 30-s intermissions, the isotonic ones - of 4 sets of extensions (both knees) at 50% of the predetermined one repetition maximum, spaced by 30-s intermissions. Heart rates (HR) and blood pressure were determined before and after the training period, both pre- and post-exercise.Results: Mean resting HR and exercise-induced HR-increase significantly decreased post-training in IT group (by 19 and 24%, respectively; p<0.001). The exercise-induced HR-increase significantly increased post-training in IK group (by 17%; p<0.001). Significant (p<0.01) training-induced decreases in the systolic pressure (SBP) were found in both training groups (IT and IK, by 7 and 6%, respectively).Conclusions: The results may be of practical importance for athletes and health professionals who administer openchain resistance exercises.
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