Impact of hydration with beverages containing free sugars or xylitol on metabolic and acute kidney injury markers after physical exercise.

The proper fluid and carbohydrates intake is essential before and during physical exercise, and for this reason most athletes drink beverages containing a high amount of free sugars. Sweetened soft drinks are also commonly consumed by those not doing any sport, and this habit seems to be both unhealthy and also the cause of metabolic problems. Recently, several sweeteners have been proposed to replace sugars in popular beverages. To examine the impact of free sugars and the popular sweetener xylitol on metabolic profile and the markers of kidney function and injury after exercise the present study was conducted with semi-professional football players. All participants were healthy, with a mean age of 21.91 years. Their sports skills were on the level of the 4th-5th division of the league. The subjects took part in four football training sessions. During each session they drank a 7% solution of sugar (sucrose, fructose, glucose) or xylitol. The tolerability of these beverages and well-being during exercise was monitored. Before and after each training session, blood and urine were collected. The markers of kidney function and injury, uric acid, electrolytes, complete blood count, CRP, serum albumin, serum glucose and the lipid profile were analyzed. The main finding of this study was that the xylitol beverage is the least tolerated during exercise and 38.89% of participants experienced diarrhea after training and xylitol intake. Xylitol also led to unfavorable metabolic changes and a large increase in uric acid and creatinine levels. A mean increase of 1.8 mg/dl in the uric acid level was observed after xylitol intake. Increases in acute kidney injury markers were observed after all experiments, but changes in urine albumin and cystatin C were highest after xylitol. The other three beverages (containing "free sugars" - glucose, fructose and sucrose) had a similar impact on the variables studied, although the glucose solution seems to have some advantages over other beverages. The conclusion is that sweeteners are not a good alternative to sugars, especially during exercise. Pure water without sweeteners should be drunk by those who need to limit their calorie consumption. Clinical Trial Registration: ClinicalTrials.gov, (NCT04310514).

The "athlete's heart" features in amateur male marathon runners.

BACKGROUND: Training on a professional level can lead to cardiac structural adaptations called the "athlete's heart". As marathon participation requires intense physical preparation, the question arises whether the features of "athlete's heart" can also develop in recreational runners. METHODS: The study included 34 males (mean age 40 ± 8 years) who underwent physical examination, a cardiopulmonary exercise test and echocardiographic examination (ECHO) before a marathon. ECHO results were compared with the sedentary control group, reference values for an adult male population and those for highly-trained athletes. Runners with abnormalities revealed by ECHO were referred for cardiac magnetic resonance imaging (CMR). RESULTS: The mean training distance was 56.5 ± 19.7 km/week, peak oxygen uptake was 53.7 ± 6.9 mL/kg/min and the marathon finishing time was 3.7 ± 0.4 h. Compared to sedentary controls, amateur athletes presented larger atria, increased left ventricular (LV) wall thickness, larger LV mass and basal right ventricular (RV) inflow diameter (p < 0.05). When compared with ranges for the general adult population, 56% of participants showed increased left atrial volume, indexed to body surface area (LAVI), 56% right atrial area and interventricular septum thickness, while 47% had enlarged RV proximal outflow tract diameter. In 50% of cases, LAVI exceeded values reported for highly-trained athletes. Due to ECHO abnormalities, CMR was performed in 6 participants, which revealed hypertrophic cardiomyopathy in 1 runner. CONCLUSIONS: "Athlete's heart" features occur in amateur marathon runners. In this group, ECHO reference values for highly-trained elite athletes should be considered, rather than those for the general population and even then LAVI can exceed the upper normal value.

Changes of Mood and Cognitive Performance before and after a 100 km Nighttime Ultramarathon Run.

Ultramarathons are becoming an increasingly popular endurance sport. Year after year, the demands on athletes' skills and endurance increase. Ultramarathons are particularly taxing on athletes' psychological functioning. This study assessed the relationships between taking part in a nighttime ultramarathon and changes in mood and cognitive functioning. The study included 20 experienced runners aged 26-57 (M = 37.29; SD = 7.94) who had M = 7.08, SD = 5.41 (range 3-44) years of experience running. There were 18 men and 2 women. The mood states were measured twice, just before the start of the run and shortly after crossing the finish line, using the Polish version of the UMACL UWIST Mood Adjective Checklist by Mathews, Chamberlain, and Jones. To assess cognitive functioning, the Stroop Color and Word Test and "Forward digit span" subtest from the Wechsler Adult Intelligence Scale were used. We observed statistically significant changes in the mood of the runners: tense arousal, associated with the experienced stress, was significantly higher before the run than immediately after the finish. Moreover, we observed an improvement in cognitive functioning after finishing the 100 km run on both of the trials on the Stroop color word test and on the forward digit span test.

Changes in Novel AKI Biomarkers after Exercise. A Systematic Review.

More than 100 substances have been identified as biomarkers of acute kidney injury. These markers can help to diagnose acute kidney injury (AKI) in its early phase, when the creatinine level is not increased. The two markers most frequently studied in plasma and serum are cystatin C and neutrophil gelatinase-associated lipocalin (NGAL). The former is a marker of kidney function and the latter is a marker of kidney damage. Some other promising serum markers, such as osteopontin and netrin-1, have also been proposed and studied. The list of promising urinary markers is much longer and includes cystatin C, NGAL, kidney injury molecule-1 (KIM-1), liver-type fatty-acid-binding protein (L-FABP), interleukin 18, insulin-like growth factor binding protein 7 (IGFBP-7), tissue inhibitor of metalloproteinases-2 (TIMP-2) and many others. Although these markers are increased in urine for no longer than a few hours after nephrotoxic agent action, they are not widely used in clinical practice. Only combined IGFBP-7/TIMP-2 measurement was approved in some countries as a marker of AKI. Several studies have shown that the levels of urinary AKI biomarkers are increased after physical exercise. This systematic review focuses on studies concerning changes in new AKI biomarkers in healthy adults after single exercise. Twenty-seven papers were identified and analyzed in this review. The interpretation of results from different studies was difficult because of the variety of study groups, designs and methodology. The most convincing data concern cystatin C. There is evidence that cystatin C is a better indicator of glomerular filtration rate (GFR) in athletes after exercise than creatinine and also at rest in athletes with a lean mass lower or higher than average. Serum and plasma NGAL are increased after prolonged exercise, but the level also depends on inflammation and hypoxia; therefore, it seems that in physical exercise, it is too sensitive for AKI diagnosis. It may, however, help to diagnose subclinical kidney injury, e.g., in rhabdomyolysis. Urinary biomarkers are increased after many types of exercise. Increases in NGAL, KIM-1, cystatin-C, L-FABP and interleukin 18 are common, but the levels of most urinary AKI biomarkers decrease rapidly after exercise. The importance of this short-term increase in AKI biomarkers after exercise is doubtful. It is not clear if it is a sign of mild kidney injury or physiological metabolic adaptation to exercise.

The Effect of Vitamin D3 Supplementation on Hepcidin, Iron, and IL-6 Responses after a 100 km Ultra-Marathon.

Deficiencies in iron and vitamin D are frequently observed in athletes. Therefore, we examined whether different baseline vitamin D3 levels have any impact on post-exercise serum hepcidin, IL-6 and iron responses in ultra-marathon runners. In this randomized control trial, the subjects (20 male, amateur runners, mean age 40.75 ± 7.15 years) were divided into two groups: experimental (VD) and control (CON). The VD group received vitamin D3 (10,000 UI/day) and the CON group received a placebo for two weeks before the run. Venous blood samples were collected on three occasions-before the run, after the 100 km ultra-marathon and 12 h after the run-to measure iron metabolism indicators, hepcidin, and IL-6 concentration. After two weeks of supplementation, the intervention group demonstrated a higher level of serum 25(OH)D than the CON group (27.82 ± 5.8 ng/mL vs. 20.41 ± 4.67 ng/mL; p < 0.05). There were no differences between the groups before and after the run in the circulating hepcidin and IL-6 levels. The decrease in iron concentration immediately after the 100-km ultra-marathon was smaller in the VD group than CON (p < 0.05). These data show that various vitamin D3 status can affect the post-exercise metabolism of serum iron.

Factors influencing post-exercise proteinuria after marathon and ultramarathon races.

Post-exercise proteinuria is one of the most common findings observed after short and intensive physical activity, but is observed also after long runs with low intensity. The aim of this study was to analyze factors influencing proteinuria after marathon runs. Two groups of male amateur runners were studied. The results of 20 marathon finishers (42.195 m), with a mean age of 49.3 ± 6.85 years; and 17 finishers of a 100-km ultramarathon with a mean age of 40.18±4.57 years were studied. Urine albumin to creatinine ratio (ACR) was calculated before and after both races. The relationship between ACR and run pace, metabolites (lactate, beta hydroxybutyrate), markers of inflammation (CRP, IL-6) and insulin was studied. The significant increase in ACR was observed after both marathon races. ACR increased from 6.41 to 21.96 mg/g after the marathon and from 5.37 to 49.64 mg/g after the ultramarathon (p<0.05). The increase in ACR was higher after the ultramarathon that after the marathon. There was no correlation between run pace and proteinuria. There was no correlation between ACR and glucose, free fatty acids, lactate, beta-hydroxybutyrate and insulin levels. There was significant negative correlation between ACR and interleukin 6 (IL-6) (r =-0.59, p< 0.05) after ultramarathon. Proteinuria is a common finding after physical exercise. After very long exercises it is related to duration but not to intensity. There is no association between metabolic and hormonal changes and ACR after marathon runs. The role on inflammatory cytokines in albuminuria is unclear.

Changes in Water Soluble Uremic Toxins and Urinary Acute Kidney Injury Biomarkers After 10- and 100-km Runs.

Acute kidney injury (AKI) is described as a relatively common complication of exercise. In clinical practice the diagnosis of AKI is based on serum creatinine, the level of which is dependent not only on glomerular filtration rate but also on muscle mass and injury. Therefore, the diagnosis of AKI is overestimated after physical exercise. The aim of this study was to determine changes in uremic toxins: creatinine, urea, uric acid, asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA), trimethylamine N-oxide (TMAO) and urinary makers of AKI: albumin, neutrophil gelatinase-associated lipocalin (uNGAL), kidney injury molecule-1 and cystatin-C (uCyst-C) after long runs. Sixteen runners, mean age 36.7 ± 8.2 years, (2 women, 14 men) participating in 10- and 100-km races were studied. Blood and urine were taken before and after the races to assess markers of AKI. A statistically significant increase in creatinine, urea, uric acid, SDMA and all studied urinary AKI markers was observed. TMAO and ADMA levels did not change. The changes in studied markers seem to be a physiological reaction, because they were observed almost in every runner. The diagnosis of kidney failure after exercise is challenging. The most valuable novel markers which can help in post-exercise AKI diagnosis are uCyst-C and uNGAL.

Changes in Serum Iron and Leukocyte mRNA Levels of Genes Involved in Iron Metabolism in Amateur Marathon Runners-Effect of the Running Pace.

Iron is essential for physical activity due to its role in energy production pathways and oxygen transportation via hemoglobin and myoglobin. Changes in iron-related biochemical parameters after physical exercise in athletes are of substantial research interest, but molecular mechanisms such as gene expression are still rarely tested in sports. In this paper, we evaluated the mRNA levels of genes related to iron metabolism (PCBP1, PCBP2, FTL, FTH, and TFRC) in leukocytes of 24 amateur runners at four time points: before, immediately after, 3 h after, and 24 h after a marathon. We measured blood morphology as well as serum concentrations of iron, ferritin, and C-reactive protein (CRP). Our results showed significant changes in gene expression (except for TFRC), serum iron, CRP, and morphology after the marathon. However, the alterations in mRNA and protein levels occurred at different time points (immediately and 3 h post-run, respectively). The levels of circulating ferritin remained stable, whereas the number of transcripts in leukocytes differed significantly. We also showed that running pace might influence mRNA expression. Our results indicated that changes in the mRNA of genes involved in iron metabolism occurred independently of serum iron and ferritin concentrations.

Biochemical Markers of Renal Hypoperfusion, Hemoconcentration, and Proteinuria after Extreme Physical Exercise.

Background and Objectives: Physical exercise increases the blood perfusion of muscles, but decreases the renal blood flow. There are several markers of renal hypoperfusion which are used in the differential diagnosis of acute kidney failure. Albuminuria is observed after almost any exercise. The aim of this study was to assess changes in renal hypoperfusion and albuminuria after a 100-km race. Materials and Methods: A total of 27 males who finished a 100-km run were studied. The mean age of the runners was 38.04 ± 5.64 years. The exclusion criteria were a history of kidney disease, glomerular filtration rate (GFR) <60 ml/min, and proteinuria. Blood and urine were collected before and after the race. The urinary albumin/creatinine ratio (ACR), fractional excretion of urea (FeUrea) and sodium (FeNa), plasma urea/creatinine ratio (sUrea/Cr), urine/plasma creatinine ratio (u/pCr), urinary sodium to potassium ratio (uNa/K), and urinary potassium to urinary potassium plus sodium ratio (uK/(K+Na)) were calculated. Results: After the race, significant changes in albuminuria and markers of renal hypoperfusion (FeNa, FeUrea, sUrea/Cr, u/sCr, urinary Na, uNa/K, uK/(K+Na)) were found. Fifteen runners (55.56%) had severe renal hypoperfusion (FeUrea <35, uNa/K <1, and uK/(Na+K) >0.5) after the race. The mean ACR increased from 6.28 ± 3.84 mg/g to 48.43 ± 51.64 mg/g (p < 0.001). The ACR was higher in the group with severe renal hypoperfusion (59.42 ± 59.86 vs. 34.68 ± 37.04 mg/g), but without statistical significance. Conclusions: More than 50% of the runners had severe renal hypoperfusion after extreme exercise. Changes in renal hemodynamics are probably an important, but not the only, factor of post-exercise proteinuria.

The VEGFA gene and anterior cruciate ligament rupture risk in the Caucasian population.

The aim of the present study was to analyse VEGFA rs699947, rs1570360, and rs2010963 polymorphisms with susceptibility to anterior cruciate ligament rupture (ACLR) in a Polish population. The study included 412 physically active Caucasian participants. The study group consisted of 222 individuals with surgically diagnosed primary ACLR qualified for ligament reconstruction (ACLR group). The control group consisted of 190 apparently healthy participants without any history of ACLR (CON group). Three polymorphisms within the VEGFA (rs699947, rs1570360, and rs2010963) gene were chosen for investigation due to their significance in the angiogenesis signalling pathway and previous associations with risk of ACLRs. Both single-locus and haplotype-based analyses were conducted. No significant differences in the allele and genotype frequency distributions were noted for the rs699947 and rs1570360 polymorphisms. In contrast, rs2010963 was associated with risk of ACLR in the codominant (p=0.047) and recessive model (p=0.017). In the latter, the CC genotype was overrepresented among individuals with ACL rupture (23.4% vs 14.2%, OR=1.85 [1.11-3.08]). Two VEGFA haplotypes were associated with ACLR under the additive (global score=11.39, p=0.022) and dominant model (global score=11.61, p=0.020). The [C;G;G] haplotype was underrepresented in the ACLR group (52.2% vs. 60.3%), whereas the [C;G;C] haplotype was overrepresented (2.9% vs 0.5%). The results obtained suggest a potential correlation between the VEGFA rs2010963 polymorphism and ACLR risk, suggesting that harbouring this specific C allele may be an unfavourable risk factor for a knee injury in Caucasian participants from Poland.

Personality Traits and Vitamin D3 Supplementation Affect Mood State 12 h Before 100 km Ultramarathon Run.

Background: Participation in extreme endurance sports is becoming an increasingly popular activity, and thus more and more people are getting involved in it. Taking part in a 100 km run is associated with great physiological and psychological stress, which can affect one's mood state. Thus, the goal of this study was to determine if personality, experience, and motives for participation are related to a runner's mood and its changes as well as to investigate whether vitamin D3 supplementation influences mood 12 h before and 12 h after the run. Method: The study group consisted of 20 experienced marathon and ultramarathon runners taking part in a 100 km track run. All participants were males aged between 31 and 50 (M = 40.75, SD = 7.15). The group was divided in two equal subgroups: the placebo group and the group supplemented with vitamin D3. Personality traits were assessed using the Polish version of Eysenck's EPQ-R 106 and mood states were measured twice (12 h before and after the run) using the Polish version of the UMACL by Mathews, Chamberlain, and Jones. Motives for participation in ultramarathons were measured with the IPAO by Lipowski and Zaleski. Results: Levels of vitamin D3 correlated very strongly with energetic arousal (EA) (rs = 0.80; p < 0.05) and strongly hedonic tone (HT) (rs = 0.74; p < 0.05) 12 h before the run. There were no significant correlations between levels of vitamin D3 and mood states after the run. Moreover, extraversion correlated moderately with tense arousal (TA) (rs = -0.48; p < 0.05) and EA (rs = 0.47; p < 0.05) while neuroticism correlated moderately with TA (rs = 0.53; p < 0.05) and HT (rs = -0.57; p < 0.05). Conclusion: Both personality and vitamin D3 supplementation are related to runners' pre-run mood. These effects are nullified when it comes to post-run mood states.

Glomerular Filtration Rate Is Unchanged by Ultramarathon.

Wolyniec, W, Ratkowski, W, Kasprowicz, K, Jastrzebski, Z, Malgorzewicz, S, Witek, K, Grzywacz, T, Zmijewski, P, and Renke, M. Glomerular filtration rate is unchanged by ultramarathon. J Strength Cond Res 32(11): 3207-3215, 2018-Acute kidney injury (AKI) is reported as a common complication of marathon and ultramarathon running. In previous studies, AKI was diagnosed on the basis of the creatinine level in serum and estimated glomerular filtration rate (eGFR). In this study, we calculated eGFR and also measured creatinine clearance after every 25 km of a 100-km run. Twenty healthy, amateur runners (males, mean age 40.75 ± 7.15 years, mean body mass 76.87 ± 8.39 kg) took part in a 100-km run on a track. Blood and urine were collected before the run, after every 25 km, and 12 hours after the run. Seventeen runners completed the study. There was increase in creatinine, urea, and uric acid observed after 100 km (p < 0.05). The mean increase in creatinine was 0.21 mg·dl (24.53%). Five runners fulfilled the AKI network criteria of AKI. The eGFR according to the modification of diet in renal disease, chronic kidney disease epidemiology collaboration, and Cockcroft-Gault formulas was significantly decreased after the run (p ≤ 0.05). Otherwise, creatinine clearance calculated from creatinine level in both serum and urine remained stable. In contrast to the majority of previous studies, we did not observe any decrease in the kidney function during an ultramarathon. In this study, the creatinine clearance, which is the best routine laboratory method to determine GFR was used. There is no evidence that long running is harmful for kidney.

Urinary Kidney Injury Molecule-1 but Not Urinary Neutrophil Gelatinase Associated Lipocalin Is Increased after Short Maximal Exercise.

BACKGROUND AND AIMS: Urinary neutrophil gelatinase associated lipocalin (uNGAL) and urinary kidney injury molecule-1 (uKIM-1) are markers of acute kidney injury. The albuminuria is a well-known abnormality after physical exercise. The aim of this study was to investigate changes in uNGAL and uKIM-1 after intensive exercise causing albuminuria. METHODS: The study population consisted of 19 participants (10 males and 9 females). The mean age of participants was 35.74 years. All were fit amateur runners; the mean body mass index was 21.99 in females and 24.71 in males. The subjects underwent a graded treadmill exercise test (GXT) according to the Bruce protocol. Maximal oxygen consumption (VO2max) was measured. Immediately before and after the test urine was collected. Urinary creatinine, albumin, NGAL, and KIM-1 were measured. Albumin to creatinine (ACR), KIM-1 to creatinine (KCR), and NGAL to creatinine (NCR) ratios were calculated. RESULTS: The mean VO2max was 53.68 in females and 59.54 mL/min/kg in males. Albuminuria and ACR were significantly higher after exercise. An increase in the ACR from 8.82 to 114.35 mg/g (p < 0.01) was observed. uKIM-1 increased significantly after exercise from 849.02 to 1,243.26 pg/mL (p < 0.05). KCR increased from 1,239.1 to 1,725.9 ng/g but without statistical significance (p = 0.07). There were no statistical changes in pre- and post-run uNGAL levels. There was no correlation between post-GXT albuminuria and uKIM-1. CONCLUSIONS: uKIM-1 is a very sensitive marker of kidney dysfunction. In our study, uKIM-1 increased significantly after a very short period of exercise. It is not clear if the increase in KIM-1 is caused by post-exercise albuminuria.

Changes in blood morphology and chosen biochemical parameters in ultra-marathon runners during a 100-km run in relation to the age and speed of runners.

OBJECTIVES: The objective of the study was to reveal morphology, electrolyte and chosen biochemical parameters in terms of health risk in runners in reference to their age and running speed in the case of running a distance of 100 km, which occur after 12 h or 24 h of recovery. MATERIAL AND METHODS: Fourteen experienced, male, amateur, ultra-marathon runners, divided into two age and two speed groups took part in the 100-km run. Blood samples for analyses indexes were collected from the ulnar vein just before the run, after 25 km, 50 km, 75 km and 100 km, as well as 12 h and 24 h after termination of the run. RESULTS: The sustained ultramarathon run along with the distance covered (p < 0.05) caused an increase in myoglobin (max 90-fold), bilirubin (max 2.8-fold) and total antioxidant status (max 1.15-fold), which also continued during the recovery. Significant changes in the number of white blood cells were observed with each sequential course and could be associated with muscle damage. The electrolyte showed changes towards slight hyperkalemia, but no changes in natrium and calcium concentrations. There were no significant differences between the age and speed groups for all the parameters after completing the 100-km run as well as after 12 h and 24 h of recovery. CONCLUSIONS: Considering changes in blood morphology and chosen biochemical parameters in ultra-marathon runners during a 100-km run it can be stated that such an exhausting effort may be dangerous for human health due to metabolic changes and large damage to the organs. Negative metabolic changes are independent of age of an ultramarathon runner and occur both in younger (32±5.33 years) and older participants (50.56±9.7 years). It can be concluded that organ damage and negative metabolic changes during a 100-km run occur similarly in participants less experienced as well as in well trained runners. Int J Occup Med Environ Health 2016;29(5):801-814.

Effect of various forms of physical training on the autonomic nervous system activity in patients with acute myocardial infarction.

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.

[The assessment of influence of long-term exercise training on autonomic nervous system activity in young athletes preparing for competitions]. / Ocena wplywu dlugotrwalego intensywnego wysilku fizycznego na czynnosc autonomicznego ukladu nerwowego w grupie sportowców przygotowujacych sie do startu w zawodach.

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.