strenuous physical activity is destructive for cardiac function causing an increased risk of myocardial infarction during and one hour after the exercise bout.1 cardiac fatigue is exercise - induced cardiac dysfunction in the absence of underlying cardiovascular diseases with a large number of symptoms and an unclear etiology.2 cardiac troponin t ( ctnt ) and troponin i ( ctni ) are regulatory proteins which are located on the contractile apparatus of the myocyte , are highly sensitive and are certain indicators of cardiomyocyte damage.3 as a result , these markers provide the tools necessary for evaluating competitive athletes from clinical point of view.3 numerous studies have suggested that prolonged exercise may induce a transient appearance of cardiac - specific troponins ( such as ctni ) , normally indicative of myocyte necrosis.46 however , most of the available literature has concerned young , well - trained athletes competing in ultra - endurance events such as an ironman triathlon or exercise of even longer duration .
limited data are available for shorter durations ( 90 min ) and intermittent exercises such as multi - sprint sports like soccer .
they showed lack of troponin in the blood that was opposite to other findings on endurance exercise.7 today , soccer players are professional athletes and changes within the game itself are creating a drive for a higher level of fitness , which requires greater versatility from players , longer playing season and greater frequency of games . because of accumulated fatigue from three or two games a week and an imbalance between training and recovery , players are at risk of becoming overtrained , subsequently increasing the possibility of cardiac damage .
therefore , the aim of this study was to monitor the physiological stress placed upon players during a typical week of a season .
the objective was to study the effects of three intermittent exercises a week and carbohydrate ( cho ) supplementation and responses of new biomarkers of cardiomyocyte injury ( ctni and ck - mb ) .
the second purpose was to create a strategy for monitoring these responses , by determining whether cho supplementation can prevent possible increase in these variables .
we examined the influence of three bouts of 90 minute high intensity intermittent exercise ( specific for soccer ) along with cho supplementation on cardiac troponin i ( ctni ) and creatine kinase - mb ( ck - mb ) in soccer players .
twelve elite soccer players were selected and divided equally into three groups of cho ( age , 22  2.6 years ; body mass , 71.7  5.4 kg ; height , 173.2  7.04 cm ) , placebo ( p ) ( age , 24.2  2.6 years ; body mass , 76.5  11.3 kg ; height , 177  12.2 cm ) , and control ( c ) ( age , 25.2  0.5 years ; body mass , 75.5  3.4 kg ; height , 176  0.8 cm ) .
they reported no symp - toms of infection or cardiovascular diseases and did not take any medications three weeks before the study .
the participants were divided into three groups ; namely , cho supplementation , placebo and control groups .
then , they performed three 90-min intermittent exercise bouts specific to soccer in one week.7 the experimental groups received cho supplementation or placebo before , during and after exercise .
the basic data ( resting state ) were collected on the first day , the ninth day ( after three sessions ) and the twelfth day ( three days after the final session ) .
in addition , blood samples were taken after each exercise session ( day two , five and eight ) for assessing acute responses .
immediately before , during and after the exercise session , fluid intake was recorded . in the carbohydrate group , participants consumed 400 ml of a lemon flavored glucose solution ( 6% ) 10 min before the start of each 45 min of exercise and 5 min after the exercise ; a further 150 ml of this solution was consumed 14 and 29.5 min into each period of exercise . in the placebo group ,
the participants consumed equal volumes of a lemon - flavored placebo drink ( containing aspartame as the sweetener ) at similar times as in the cho group .
the participants reported on the laboratory at 08:00 oclock on each occasion , after an overnight fast .
blood samples ( 10 ml ) were taken from an antecubital vein after each exercise protocol and in resting states ( day 1 , 9 and 12 ) .
each exercise protocol comprised two periods of intermittent exercise ( 45-min each ) that simulated the activity patterns of a soccer match , using the activity profile described by bangsbo et al.8 the two periods were separated by a 15 min half - time interval .
each bout was separated by 1.5 min of rest , during which 150 ml of the prescribed drink was consumed .
the bouts comprised seven circuits of 2 min each : 50 m dribbling the ball through cones placed 5 m apart , 50 m back - wards running , 25 m cruising , 25 m sprinting and 50 m walking.9 any remaining time at the end of each 2 min circuits was a rest period
. a total distance of approximately 9.7 km was covered during the 90-min exercise protocol .
this distance is similar to that reported to be covered during english first division matches by midfield players.10 blood samples were collected into two separate vacutainer tubes , one containing tripotassium ethylene diamine tetraacetic acid ( k3edta ) and the other containing lithium heparin .
the quantitative determination of ctni and ck - mb in the serum was performed on the liaison analyzer .
a monoclonal antibody was used for the coating of the solid phase ( magnetic particles ) and a polyclonal antibody ( goat ) was used for the tracer .
the liaison analyzer automatically calculates the troponin i concentration in each sample by means of a calibration curve generated by a two - point calibration master curve procedure .
dependent t - tests were used for comparing any significant difference of each group on the first day .
analyses of variance with repeated measures were used for determination of any significant difference in any variables in the six days of sampling .
one - way analysis variance was used for detection of any significant difference between groups in each phase .
twelve elite soccer players were selected and divided equally into three groups of cho ( age , 22  2.6 years ; body mass , 71.7  5.4 kg ; height , 173.2  7.04 cm ) , placebo ( p ) ( age , 24.2  2.6 years ; body mass , 76.5  11.3 kg ; height , 177  12.2 cm ) , and control ( c ) ( age , 25.2  0.5 years ; body mass , 75.5  3.4 kg ; height , 176  0.8 cm ) .
they reported no symp - toms of infection or cardiovascular diseases and did not take any medications three weeks before the study .
the participants were divided into three groups ; namely , cho supplementation , placebo and control groups .
then , they performed three 90-min intermittent exercise bouts specific to soccer in one week.7 the experimental groups received cho supplementation or placebo before , during and after exercise .
the basic data ( resting state ) were collected on the first day , the ninth day ( after three sessions ) and the twelfth day ( three days after the final session ) .
in addition , blood samples were taken after each exercise session ( day two , five and eight ) for assessing acute responses .
immediately before , during and after the exercise session , fluid intake was recorded . in the carbohydrate group , participants consumed 400 ml of a lemon flavored glucose solution ( 6% ) 10 min before the start of each 45 min of exercise and 5 min after the exercise ; a further 150 ml of this solution was consumed 14 and 29.5 min into each period of exercise . in the placebo group ,
the participants consumed equal volumes of a lemon - flavored placebo drink ( containing aspartame as the sweetener ) at similar times as in the cho group .
the participants reported on the laboratory at 08:00 oclock on each occasion , after an overnight fast .
blood samples ( 10 ml ) were taken from an antecubital vein after each exercise protocol and in resting states ( day 1 , 9 and 12 ) .
each exercise protocol comprised two periods of intermittent exercise ( 45-min each ) that simulated the activity patterns of a soccer match , using the activity profile described by bangsbo et al.8 the two periods were separated by a 15 min half - time interval .
each bout was separated by 1.5 min of rest , during which 150 ml of the prescribed drink was consumed .
the bouts comprised seven circuits of 2 min each : 50 m dribbling the ball through cones placed 5 m apart , 50 m back - wards running , 25 m cruising , 25 m sprinting and 50 m walking.9 any remaining time at the end of each 2 min circuits was a rest period .
this distance is similar to that reported to be covered during english first division matches by midfield players.10
blood samples were collected into two separate vacutainer tubes , one containing tripotassium ethylene diamine tetraacetic acid ( k3edta ) and the other containing lithium heparin .
the quantitative determination of ctni and ck - mb in the serum was performed on the liaison analyzer .
a monoclonal antibody was used for the coating of the solid phase ( magnetic particles ) and a polyclonal antibody ( goat ) was used for the tracer .
the liaison analyzer automatically calculates the troponin i concentration in each sample by means of a calibration curve generated by a two - point calibration master curve procedure .
dependent t - tests were used for comparing any significant difference of each group on the first day .
analyses of variance with repeated measures were used for determination of any significant difference in any variables in the six days of sampling .
one - way analysis variance was used for detection of any significant difference between groups in each phase .
results of this study showed that three bouts of 90-min exercise along with carbohydrate do not have any significant effect on the level of ctni .
however , there was a significant difference in ck - mb values after the second and third session compared to the first day ( p < 0.05 ) .
comparison of the three groups in different days showed significant differences between cho and p groups after the first and second session ( p < 0.05 ) .
mean  sd level of ctni ( ng / ml ) in studied grops mean  sd level of ck - mb ( ng / ml ) in studied patients
the aim of this study was to examine the influence of high - intensity intermittent exercise and cho supplementation on ctni and ck - mb in soccer players .
the results of this study showed no significant difference between pre - exercise values of ctni in three groups after three exercise sessions or in resting states .
other findings of this study showed that cho supplementation has significant influences on serum ck - mb .
although not entirely unanimous , numerous studies have suggested that prolonged exercise may induce a transient promotion in the appearance of cardiac - specific troponins , such as ctni , normally indicative of myocyte necrosis.24561112 to date , most of the available literature is on well - trained athletes competing in a range of ultra endurance activities .
there are no data for individuals taking part in moderate duration exercise with intermittent periods of high intensity exercise like soccer and other team sports .
owing to the extended duration of activities reported in previous studies , this type of exercise tends to be relatively submaximal and steady state in nature .
such events contain very limited periods of intense cardiovascular acceleration or deceleration that may increase myocardial oxygen demand . to our knowledge , there is only one study on young healthy subjects taking part in high - intensity intermittent exercise of 90 min.7 george et al found a lack of troponin in the blood samples of the subjects.7 present findings suggest that this type of exercise does not result in myocyte necrosis or alteration in membrane permeability . therefore , further research is required to understand the effects of such type of exercise on cardiac markers . however ,
results of previous studies about continuous ultra - endurance activities were inconclusive . some studies on events such as race across the alps5 and ultra - endurance mountain marathon11 reported an increase in these biomarkers .
on the other hand , some studies on exercises like marathon612 and triathlon13 showed no increase in these markers .
therefore , with respect to uncertainty regarding increase of the troponins after ultra endurance activities , it is critical to be sure that exercises such as soccer with lower duration and intensity , even with three exercises a week , lead to increase in these biomarkers .
however , bearing in mind the appearance of sudden death in soccer during the recent years , it is important to study chronic effects of intermittent exercises such as soccer on understanding exercise - induced cardiac injuries .
in conclusion , in spite of the mild increase in ck - mb that may result from the intermittent and explosive nature of the exercise protocol and muscle injuries , our findings suggest that performing three 90-min intermittent exercises a week may lead to significant variations in the cardiac markers
. however , it is important to consider higher intensities of a real soccer match and repeating this pattern over longer term periods of time .
 objectives : the aim of this study was to examine the influence of high - intensity intermittent exercise and carbohydrate supplementation on cardiac troponin i ( ctni ) and creatine kinase - mb ( ck - mb ) in soccer players.methods:twelve elite soccer players were selected and divided equally into three groups of carbohydrate ( cho ) , placebo ( p ) and control ( c ) . 
 blood samples were taken in six phases and were analyzed with the chemiluminescence method.results:results showed that three bouts of 90-min exercise along with carbohydrate supplementation did not have any significant effect on the level of ctni indices . 
 however , there was a significant difference in ck - mb values after the second and third sessions compared with the first day ( p < 0.05).conclusion : in summary , exercises with less duration and intensity like soccer do not seem to be effective on ctni and ck - mb . 
 when the overall intensity of exercise was moderate , it appeared that carbohydrate supplementation had less effect on the alteration of biochemical markers of the myocardial muscle . 
INTRODUCTION
METHODS
Participants
Experimental procedures
Blood analysis
Statistical analysis
RESULTS
DISCUSSION
CONCLUSION