exercise is one of the most powerful non - pharmacological method of affecting cells and 
 organs in the body1 .
regular aerobic and 
 resistance exercise training has a positive long - term impact on the cardiovascular system , 
 which is a biologically complex adaptive system that is characterized by a variety of 
 complex reactions to different training loads2,3,4 . while performing exercise , it is important that the body is supplied with oxygen and energy 
 substances .
this transporting function is performed by the cardiovascular system5 . the power to transport these substances to 
 cells
it has been known for long 
 that blood flow intensification or even more accurate blood flow redistribution during 
 exercise can increase blood supply to working muscles and consequently increase working 
 capacity6 .
nowadays , athletes and 
 coaches are looking for the most efficient training method so as to achieve maximum results 
 and to maintain these results for the longest possible period of time in order to minimize 
 the probability of injury . recently , an unconventional training method has been developed 
 that uses blood flow restriction in the musculoskeletal system , otherwise known as the 
  kaatsu  methodology .
an example of this is a walking workout using blood flow restriction , 
 which has been proven to be a useful method of improving muscle function , including muscle 
 hypertrophy , strength , and endurance .
one of the potential ways to achieve 
 this could be training with blood flow restriction7 , 
 8 .
training with less weight reduces 
 stress on joints and therefore minimizes the possibility of getting injured .
recently , blood 
 flow restriction combined with low - intensity resistance exercise has been suggested as a 
 useful exercise protocol to gain muscular strength and mass without an increase in blood 
 pressure9 .
some authors have 
 suggested using as little as 20% of the maximum repetition weight during the training with 
 blood restriction . as it is almost impossible to evaluate large arterial function directly ,
recording 
 of an electrocardiogram ( ecg ) is one of the most practical noninvasive methods . in 
 application of the ecg in sports physiology , st - segment depression is the key index that 
 refers to the degree of the occurrence of myocardial ischemia .
this is of special 
 significance in adolescent or young athletes , as it can be used to recognize unphysiological 
 states during workouts .
together hereditary and congenital abnormalities of the heart are the most common causes of 
 nontraumatic death in sport in young athletes . in middle - aged recreational athletes ,
more 
 than 90% of sudden cardiac deaths occur in males , and more than 90% are caused by 
 atherosclerotic coronary artery disease10 .
such findings encourage a greater interest in noninvasive ecg 
 methods of research and in questioning the meaning of st - segment depression at different 
 workout and rest stages .
. 
 basically , corrected qt or jt interval ( qtc , jtc ) indices increases sudden death and other 
 risks11 .
however , some ecg parameters 
 observed in a minority of athletes present diagnostic conundrums .
the jt interval 
 ( measured from the j - point up to the end of the t - wave ) describes the 
 duration of ventricular repolarization , and shortening of the jt interval during physical 
 load correlates with the increase in metabolic rate in the myocardium12 .
our hypothesis states that the training gain achieved by training with the circulatory 
 restriction applied during low - intensity exercising lies within the physiological limits of 
 the cardiovascular system .
the aim of this study was to the effect of a single occlusion 
 training session on the cardiovascular response to bouts of exercise .
the 
 subjects in the study were amateur athletes in track and field with 46  years of training 
 experience , and they participated in two groups : a control group without blood flow 
 restriction and experimental group with blood flow restriction ( n=24 , mean age 22.5  
 1.5  years ; body mass index 24.7  0.5  kg / m ) .
the weight and body mass index 
 ( bmi ) ( tbf-300 body composition scale ; tanita , uk ltd .
, west drayton , uk ) of the subjects 
 were estimated while they were seminude ( shorts and t - shirts ) .
none of the subjects 
 exercised for at least 12 hours and before the test or ate for at least 2 hours before the 
 test .
the physical load test was carried out during the competitive period of the sports 
 season .
the study was designed to determine the effects of a single occlusion training session on 
 the cardiovascular system .
the participants underwent circulatory restriction with a 
 40-mm - wide cuff applied the groin13 .
the 
 participants were seated on a calf muscles trainer , and the cuff air pressure was set at 120 
 mmhg ( the approximate resting systolic blood pressure for each participant14 . in this study ,
the calf muscles 
 ( m. gastrocnemius and m. soleus ) and the sole flexion muscle ( m. 
 flexor digitorum brevis ) were impacted by the occlusion . as part of a coherent 
 muscular system ,
the knee of the working leg was fixed at an angle of 
 90 , and the ankle was fixed at an angle of 70. the dynamometer was adjusted according to 
 the foot size of the participant
. maximum voluntary contraction ( mvc ) , measured in newton s 
 ( n ) , was performed three times , and the highest value was recorded .
mvc was measured only 
 before training in order to choose the individuals training workload .
arterial blood pressure ( abp ) , an important cardiovascular functional parameter , was 
 measured using the cuff method and by listening to the  korotkoff tones .
a computerized analysis system  kaunas - load  was employed for continuous 12-lead ecg 
 registration and analysis .
changes in rr interval or heart rate ( hr ) , jt interval , 
 st - segment depression ( sum of negative values for 12 leads ) , and in ratio 
 of the jt / rr intervals were analysed .
as shown in other studies , low - intensity resistance exercise training with occlusion 
 ( 2050% mvc ) increases both muscle cross - sectional area and strength15 .
therefore , we used a single session of training with an 
 exercise intensity of 40% mvc .
foot flexor muscle conditioning training was conducted as 
 follows : three exercises comprising of the three sets of eight repetitions per set for each 
 leg .
a 2.5-min rest period was provided between exercises , and a 30-sec rest period was 
 provided between sets .
the participants were asked to lift the weight in time with a 
 metronome ( 30 movement cycles per minute)16 .
occlusion was applied before the exercise and was removed after 
 each set of three exercises ( 3 sets , 3 exercises per set , and 8 repetitions per 
 exercise ) .
the arithmetic mean ( x ) , standard deviation ( s ) , and the arithmetic mean of the error 
 ( sx ) were calculated .
a two - way independent samples student s t - test was used 
 to determine how reliable the mean difference was for performance indicator results . a 
 significant difference between compared values
this study was approved by the regional biomedical research ethics committee ( lithuanian 
 university of health sciences , kaunas , lithuania ) ( no : be-210 , 2603 - 2015 ) .
the results of the research showed that before the exercise , the average hr was 69.1  4.0 
 beats / min .
hr showed a significant 
 increase during exercise , increasing to 96.3  4.9 beats / min in the experimental group and 
 to 94.1  3.8 beats / min in the control group . during recovery from the first set , hr was 
 84.8  5.4 beats / min in the subjects with the circulatory restriction , while the value for 
 the other group was 82.0  3.1 beats / min .
1.changes in heart rate during exercise and at rest , the changes in the hr during the first set were the same in both groups ; however , 
 continuation of the exercise tasks revealed that the values after each set in the control 
 were higher than those in the experimental group .
changes in heart rate during exercise and at rest before the study , there was no significant statistical difference between the groups when 
 comparing both systolic and diastolic abp ( p<0.05 ) . in addition
, we did not find any 
 difference between groups in terms of changes in diastolic abp during exercise , and we 
 observed a low tendency for systolic abp to increase in response to repeated sets of 
 exercise ( table 1table 1.average increase in systolic and diastolic abp during exercise setssystolic ( mmhg)diastolic ( mmhg)set 1set 2set 3set 1set 2set 3experimental10.3  3.510.6  2.911.6  3.24.6  3.53.0  3.83.7  3.3control7.6  4.19.0  3.412.6  4.02.0  3.11.9  3.41.8  2.7 ) . at the onset of exercising ,
the applied occlusion had no influence on st - segment depression during 
 exercise or at rest .
jt / rr values registered before exercise during the rest and while at 
 first set of exercises were not significantly different ; however , a tendency for a lower 
 increase in jt / rr during the repeated exercise sets performed with partial circulatory 
 restriction was observed ( fig .
the cardiovascular system , is a vital body system and the model of human body response to 
 exercising12 outlines it as the most 
 important part of the supplying systems .
results obtained during this study revealed that 
 the increase in hr during the exercise was more notable in the control group compared with 
 the experimental group . it was also determined that the application of the partial 
 circulation restriction caused lower jt / rr ratio values in the ecg . in assessing these 
 findings
as it was 
 shown by other authors17 , the jt / rr ratio 
 allows depiction of the mobilization of the cardiovascular system during exercising .
if we 
 were to multiply the abovementioned ratio by 60 , it would allow us to depict the situation 
 over time , that is , how many seconds per minute the heart ( myocardium ) was contracted and 
 consequently how long the cardiac musculature was at rest .
the data from this study indicate 
 that cardiac muscle strain was slightly lower when the low - intensity exercise was carried 
 out with a partial circulatory restriction .
the present study found that systolic and diastolic abp were higher throughout the entire 
 study .
this corresponds to the findings of other research 
 showing that application of occlusion increases vascular wall elasticity19 .
it is important to note that vascular 
 wall elasticity is one of the main factors that affect diastolic arterial blood pressure . 

the fact that certain blood vessels were clamped during the research could have also 
 influenced the increase of diastolic abp . performing the exercised with partial circulatory 
 restriction
is not just healthier for joints ( as smaller weights are used ) ; a previous study 
 also showed that no manifestations of thrombosis where observed when using occlusion20 .
the heart reserve possibility 
 of largely depends on whether the demand for oxygen is satisfied and on as how quickly and 
 sufficiently oxygen is delivered to the heart during the exercise .
when the myocardium is 
 insufficiently supplied with blood there is a lack of oxygen in the myocytes .
when coronary 
 heart blood vessels are insufficiently supplied with blood , during the exercise , changes 
 occur in the balance of metabolic processes and subsequently in electric potentials of 
 myocytes . as a result of these processes , st - segment depression is visible in ecg records . 

thus assessment of the degree of ischemic episodes during exercise is also essential and 
 indicates the functional state of the heart .
partial blood flow restriction had an ambiguous effect on blood pressure changes during the 
 exercise .
systolic abp values continued to be higher during the exercise , while changes in 
 diastolic abp were not registered . repeating the exercise increased fatigue , and the body 
 was forced to mobilize more and more resources to perform a given exercise task .
therefore , 
 in the analysis of the research results , we assessed manifestations of variations in 
 functional indices of the cardiovascular system , i.e. , changes of mobilization and recovery . 

we concluded that when a partial blood flow restriction was applied during repeated 
 exercise , the heart mobilization and recovery features were better reflected in the jt / rr 
 ratio than in hr . in assessment of manifestations of hr fluctuations , it was found that the amplitude of hr 
 change in response to exercise repetitions remained the same , while the increase in 
 mechanical work duration of the myocardium , as indicated by the jt / rr ratio , was lower , 
 which can be interpreted as indicating that the heart could perform its pumping function 
 with more ease .
this was confirmed by the changes in jt in the ecg data , which demonstrated 
 changes in exactly the same direction .
the physiological sense of jt can be defined as 
 follows : the jt interval in a recorded ecg is measured from the connection point j to the 
 end of the t wave ( point j corresponds to the moment when the ecg curve after the s wave 
 returns to isolines ) .
the jt interval indicates ventricular repolarization processes and can 
 be used as an indicator of the repolarization duration .
also jt interval variation is 
 related to changes in the intensity of myocardial metabolism21 , 22 . despite
all the provided positive conclusions on the subject , we can not affirm that 
 exercise should be performed only by applying the occlusion training method .
firstly , it 
 requires special equipment , the ability to use the special equipment , and knowledge of the 
 application procedures . secondly , there are authors who claim that training with occlusion 
 does not provided reliable results23 .
on 
 the other hand , in a study made by maior in 2015 , an interesting conclusion was drawn that 
 is application of occlusion training is more effective when movement is carried out through 
 one joint24 , 25 .
thus , no unanimous conclusion can be made at present , but perhaps 
 scientists will carry out more research in the future to determine the body s response to 
 applying blood flow restriction with different pressure levels . in summary
we conclude that applying partial blood flow restriction with occlusion training 
 in the groin area resulted in a lower degree of hr increase in response to repeated exercise 
 compared with training without occlusion .
however , this partial blood flow restriction does 
 not increase the myocardium load and has no significant effect on coronary vascular 
 function .
partial blood flow restriction affects the change in blood pressure during 
 exercise in an ambiguous way .
systolic abp values continue to be higher during the change in 
 blood pressure , while diastolic abp changes are not expressed . in conclusion , this study 
 confirmed the hypothesis that there is no additional strain on cardiac functioning during 
 occlusion training carried out by exercising with partial blood flow restriction in the 
 groin area .
the results obtained during the study suggest that such kind of occlusion training could be 
 applied for health training and rehabilitation purposes .
occlusion training by using a low 
 intensity of exercise triggers changes in muscular tissue similar to high - intensity exercise 
 training .
meanwhile , the cardiovascular system during exercise does not experience higher 
 overload , which could be a risk factor for cardiac patients and physically inactive persons . 

 [ purpose ] occlusion training with low - intensity resistance exercises and blood flow 
 restriction increases muscle cross - sectional area and strength . 
 this form of training is 
 used in rehabilitation ; therefore , the aim of this study was to examine the effect of one 
 occlusion training session on the cardiovascular response to bouts of exercise . 
 [ subjects 
 and methods ] two groups took part : a control group without blood flow restriction and an 
 experimental group with blood flow restriction . 
 a single training session was used with 
 the exercise intensity set at 40% of the one repetition maximum . 
 maximum voluntary 
 contraction , arterial blood pressure , and electrocardiogram measurements were performed . 
 
 [ results ] heart rate was slightly higher in the control group . 
 the performed training had 
 no effect on diastolic blood pressure in either group , however , a tendency for a small 
 systolic blood pressure increase was observed during the session in the experimental 
 group . 
 jt interval changes did not reveal significant differences between groups . 
 there 
 were no significant changes in st - segment depression during the exercise or at rest . 
 a 
 lower tendency for jt / rr increases was observed during the repeated exercise tasks with 
 partial blood flow restriction . 
 [ conclusion ] low intensity exercises carried out with a 
 partial blood flow restriction do not result in significant overload of cardiac 
 function . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION