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BACKGROUND: A shift in the dynamic autonomic nervous system (ANS) balance towards sympathetic activity in patients with acute myocardial infarction (AMI) predisposes them to life-threatening ventricular arrhythmias. Improvement of unfavourable changes in ANS can be expected in such patients as a result of physical training. A beneficial shift in ANS balance towards parasympathetic activity could be confirmed by demonstrating increased baroreceptor reflex sensitivity (BRS) as well as favourable changes in heart rate variability (HRV) parameters. AIM: To analyse the effect of different forms of physical training on ANS activity in patients with AMI after hospital discharge. METHODS: The study included 38 patients with AMI (aged 59 ± 8 years) subjected to 2-month exercise training. Group 1 (n = 19)underwent 3-week supervised in-hospital cardiac rehabilitation followed by 5-week home-based training, and Group 2 (n = 19) underwent 8-week home-based training. BRS and HRV were determined based on a 10-min recording of systolic arterial pressure and the cardiac cycle. Measurements were performed one day before discharge (R1) and after 2 months of training (R2). RESULTS: A significant increase in the mean values of TP (total power), HF (high frequency power), rMSSD (square root of the mean of the squared differences between successive R-R intervals), and pNN50 (proportion of differences between successive R-R intervals that are greater than 50 ms) was observed in the overall study group, along with trends for higher SDNN (standard deviation of the mean of sinus rhythm R-R intervals) and HFnu (normalised HF power), and for lower LFnu (normalised LF power). Additionally, a significant increase in BRS (from 2.2 ± 0.6 to 5.1 ± 2.2 ms/mm Hg, p = 0.01) was found in patients with baseline BRS ≤ 3 ms/mm Hg. A significant increase in rMSSD, pNN50, HF and HFnu, as well as a decrease in LFnu and LF/HF (LF to HF ratio) was observed in Group 1. In contrast, a significant increase in BRS was noted in Group 2. CONCLUSIONS: Various forms of 2-month physical training led to a favourable shift in autonomic balance towards parasympathetic activity. Our findings suggest a clinically important effect of physical activity in patients after AMI.

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UNLABELLED: The exercise training has positive impact on autonomic nervous system (ANS) activity. However, specific type of these changes significantly depends on intensity of used physical exertion. THE AIM OF THE STUDY: To assess the influence of long-term and single moderate physical exertion on ANS function in young athletes. MATERIAL AND METHODS: Sixteen middle-aged, 19-34 years old (24 +/- 5) athletes were included in the study. Assessment of ANS parameters (baroreflex sensitivity--BRS-WBA, heart rate variability--HRV) and mean heart rate period (mean HP) were calculated three times: recording 1--during the final stage of training period, recording 2--60 minutes after single moderate exertion, recording 3--after 2 months of training before competitions. RESULTS: In the whole group, significant increase of TP, HF SDNN and rMSSD indices was found in recording 2 comparing to recording 1, whereas after 2 months of intensive training no statistically significant changes were observed. In the group of athletes training only endurance sport (12 persons) in recording 2 the significant increase of TP, HF, SDNN, rMSSD and BRS-WBA was found. After 2 months of intensive training, no changes of these parameters were observed. CONCLUSIONS: In response to long-term training cycle with increasing intensity, preparing athletes for competitions, no significant changes of measured ANS parameters were found, which may indicate lack of overtraining during such a high intensity of training, and its safety. The changes of ANS parameters indicating increase of parasympathetic nervous system function after single exertion with moderate intensity (65% of maximum heart rate) were observed.

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INTRODUCTION: Moderate-intensity endurance training causes increased parasympathetic activity while very intensive (extreme) exercise loads may lead to persistently elevated sympathetic tone in champion class athletes preparing for competitions. Exercise training loads used by regional class sportsmen are usually somewhat less intensive. AIM: To assess the changes in autonomic nervous system activity in a group of regional class runners during a long-term training cycle preparing them for competitions. METHODS: Twenty-four regional class runners (including 22 males) with a mean age of 24+/-4 years (18 to 34 years) were enrolled in the study. Resting heart rate (mean HR) and autonomic system tone were assessed in the final period of the preparatory training (1) and in the terminal phase of the competition period (2). Additionally, ten-minute long continuous non-invasive acquisitions of systolic arterial blood pressure--SAP (Finapress, Ohmeda) and heart rate period--HP (Mingograf 72oC) were carried out in each subject. Then arterial baroreflex sensitivity by means of spectral analysis (BRS_WBA) and indices of heart rate variability (SDNN, pNN50, RMSSD, TP, LF, LFnu, HF, LF/HF) were calculated from the recorded SAP and HP signals. RESULTS: A statistically significant increase in indices of heart rate variability such as BRS_WBA, SDNN, pNN50, TP and LF in period 2 when compared with period 1 was found. Their values were 17.2+/-8.2 vs 11.5+/-5.1 ms/mmHg (p=0.0001), 91+/-55 vs 70+/-36 ms (p=0.0002), 48+/-24 vs 38+/-23% (p=0.03), 4364+/-2614 vs 3384+/-2298 ms2 (p=0.01), 2262+/-2031 vs 1398+/-1203 ms2 (p=0.002), respectively. Borderline elevation of the RMSSD index (83+/-62 and 67+/-37 ms respectively for period 1 and period 2; p=0.09) was also noted. The other calculated parameters did not differ significantly. CONCLUSIONS: Long-term intensive exercise training, employed by regional class runners preparing for competitions, changes the autonomic profile, promoting parasympathetic dominance. This may be an important argument to encourage many young and healthy people to engage in endurance sports at such intensity.

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UNLABELLED: Initial response of human body to exercise consists of a decrease in vagal tone, followed by an increase in sympathetic activity. After exercise cessation, the parasympathetic component quickly regains its pre-exercise level, whereas signs of sympathetic activation have been reported to persist as long as 24 hours after intense exercise. AIM: To verify in a group of young marathon runners whether extreme endurance exercise may induce an increase of sympathetic activity for up to 48 hours during recovery. MATERIAL AND METHODS: Twelve athletes aged 32+/-12 years, taking part in a marathon (42 km) were studied. We measured baroreflex sensitivity using the transfer function method (BRS-WBA), as well as standard spectral indexes of short-term heart rate variability (LF and HF power, LFnu, LF/HF). These parameters were measured before the marathon and on the second day (about 48 hours) following the event. Comparisons were made between the two measurements (after vs. before). RESULTS: We found a statistically significant decrease in BRS-WBA (15.1+/-4.5 vs. 10.5+/-3.5 ms/mmHg, p=0.013), as well as a trend towards higher values of LF/HF (1.0+/-1.0 vs. 1.4+/-1.4, p=0.09). An increase in LF (from 1048+/-874 to 1427+/-1678 ms2) was observed, but it did not reach statistical significance. CONCLUSIONS: These results suggest that increased sympathetic activity can persist for up to 24 hours after an extreme endurance exercise such as a marathon. It is thus likely that in less trained and less physically active people exposed to excessive amounts of strenuous exercise, the autonomic nervous system response can be similar. Further studies are needed, however, to verify this inference.

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BACKGROUND: The aim of the present study was to investigate the effect of a single bout of mild exercise on autonomic nervous system activity in healthy subjects. METHODS AND RESULTS: The study group comprised 18 healthy males, aged between 20 and 24 years, who had not been training regularly for the last 3 months. A supine recording of systolic arterial pressure (SAP) and RR interval and the administration of the phenylephrine test were performed at baseline and repeated after a 60-min recovery period following treadmill exercise training for 30 min at 65% of maximal heart rate. Mean SAP and RR interval, heart rate variability (HRV) indices (the standard deviation of normal-to-normal RR intervals (SDNN), the square root of the mean of squared differences between successive intervals and the percentage of adjacent RR intervals differing more than 50 ms), noninvasive spectral baroreflex sensitivity (Spe-BRS) and phenylephrine baroreflex sensitivity (Phe-BRS) were assessed before and after training. Mean SAP measured after exercise was lower than baseline (120+/-12 mmHg vs 128+/-12 mmHg, p = 0.05). Spe-BRS and Phe-BRS increased significantly after exercise, from 11.8+/-6.1 ms/mmHg to 16.0+/-7.8 ms/mmHg (p = 0.034), and from 16.0+/-8.8 ms/mmHg to 21.9+/-9.3 ms/mmHg (p = 0.022), respectively. A parallel increase was also observed in SDNN (from 81+/-44 ms to 96+/-53 ms, p = 0.02), but the other HRV indices showed no significant differences between pre- and post-exercise. CONCLUSIONS: A single session of mild exercise performed by sedentary young men leads to significant autonomic nervous system improvement, which suggests that even mild physical activity is beneficial for neural cardiac regulation and should be recommended to sedentary healthy subjects.

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