exercise facilitates metabolic functions in the human body and benefits physical health by 
 preventing disease , controlling weight , and maintaining homeostasis1 .
the american heart association reported that a lack of 
 exercise is one of the main factors of heart disease ( along with high blood pressure , 
 hyperlipidemia , and smoking ) and recommended regular exercise to treat and prevent 
 heart - related disease2 . measuring the blood biochemical indicators of myocardial damage
is conventionally divided 
 into a traditional method that measures creatine kinase myocardial band isoenzyme ( ck - mb ) 
 and a cardiac enzyme test that measures cardiac troponin ( ctn ) .
an increase in these 
 elements indicates a strong possibility of acute cardiac infarction3 . of these elements
, ctn is an enzyme specific to the heart 
 that increases in response to very small cardiac damage4 .
therefore , ctn is a standard biochemical index used for diagnosing 
 myocardial necrosis in patients with coronary artery disease5 .
the n - terminal of prohormone brain natriuretic peptide ( nt - probnp ) 
 is an indicator that is useful for diagnosis , the evaluation of treatment effects , and the 
 prediction of the prognosis of patients with cardiac insufficiency .
nt - probnp is also known 
 to be effective for predicting a malfunction of the left ventricle after cardiac 
 infarction6 .
the material reflects 
 cardiac stress in clinics and has been reported to be excessively expressed over the normal 
 range during serious exercise , such as an ultra - marathon7 . performing regular exercise before fierce endurance exercise is 
 effective for preventing myocardial and muscular tissue damage during the fierce endurance 
 exercise .
however , few studies have examined the physiological indicator in cases of one - off 
 high - intensity exercise after moderate- or high - intensity endurance orientation training . 

therefore , the purpose of this study was to investigate differences in the concentrations of 
 ctni , nt - probnp , and ck - mb in male sprague - dawley rats during one bout of prolonged 
 treadmill exercise ( lasting 3 h ) following different training and non - training regimens .
forty male sprague - dawley rats ( age : six weeks , weight : 150180  g each ) were used in this 
 study .
all animals were housed ( three rats per cage ) at 23  2  c and 50  5% humidity with 
 a 12-hour light  dark cycle .
the rats were given a seven - day period for adapting to the 
 environment before the experiment .
the rats were randomly divided into four groups ( n=10 in each 
 group ) : control , high - intensity exercise , moderate - intensity exercise , and nonexercise .
this 
 study was approved by the institution of animal care and use committee of daegu university , 
 and the experimental procedure complied with the management guidelines for experimental 
 animals .
the exercise intensity levels used in this study were set on the basis of the results of a 
 study by shepherd and gollnick ( 1976 ) , in which the maximal oxygen uptakes of white 
 sprague - dawley rats were measured using a metabolic rate - measuring instrument and a 
 treadmill . as a result
, the levels were set at 15 m / min ( i.e. , approximately 65% of the 
 maximal oxygen uptake ) and 28 m / min based on the reference data that defined the relevant 
 velocity as being approximately 82% of the maximal oxygen uptake8 .
this study s aerobic exercise groups first performed a 
 preliminary aerobic adjustment exercise for 20  min daily for four days and then performed 
 their main treadmill training for 35  min / day six days per week ( except sunday ) for four 
 weeks .
the high- and moderate - intensity exercise groups maintained intensity levels of 28 
 m / min and 15 m / min , respectively .
but , non - exercise group carried out preceding exercise for 
 four days and since then did nt carry out intensive aerobic exercise . after the training , 
 the high- and moderate - intensity exercise groups and the nonexercise group simultaneously 
 performed one bout of prolonged treadmill exercise at 15 m / min for 3  h. following this bout of prolonged treadmill exercise , the animals were weighed .
each animal s abdominal cavity was 
 dissected immediately , and 10  ml of blood was collected from the main artery using a 
 syringe .
the collected blood was put into an eppendorf tube and centrifuged at 18,000  rpm at 
 4  c for 18  min .
the collected sera were stored in a freezer at 70  c prior to analysis . 

, usa ) was used as a measurement device , and a dimension mmb 
 flextm reagent cartridge was used as a reagent .
the blood threshold applied to each 
 experiment was under 0.6 ng / ml and 125 pg / ml for ctni and np - probnp , respectively .
a one - way analysis of variance test was performed using pasw ( version 18.0 for windows ) to 
 investigate intergroup differences .
table 1table 1.results of prolonged intensive exercise in rats accustomed to high- and 
 moderate - intensity trainingcg ( n=10)hg ( n=10)mg ( n=10)ng ( n=10)weight ( g)230 g220 g220 g230 gctni ( ng / ml)0.01  0.000.08  0.020.59  0.40*1.54 
0.74*nt - probnp ( pg / ml)27.8  8.729.7  10.538.5  12.858.5  15.3**p<0.05 .
cg : control group ; hg : high - intensity group ; mg : moderate - intensity group ; ng : 
 non - exercise group . * significantly different compared with cg ( p<0.05 ) ; significantly different 
 compared with ng ( p<0.05 ) presents the weights of the rats measured in each exercise group after one 
 bout of prolonged treadmill exercise .
the ctni levels differed significantly between the 
 groups : 0.01  0.00 ng / ml for the control group , 0.08  0.02 ng / ml for the high - intensity 
 exercise group , 0.59  0.40 ng / ml for the moderate - intensity group , and 1.54  0.74 ng / ml 
 for the non - exercise group ( p<0.05 ) .
the post hoc analysis showed that the high- and 
 moderate - intensity exercise groups had significantly higher ctni levels than the control 
 group ( p<0.05 ) , and the high- and moderate - intensity exercise groups had significantly 
 lower ctni levels than the non - exercise group ( p<0.05 ) ( table 1 ) .
cg : control group ; hg : high - intensity group ; mg : moderate - intensity group ; ng : 
 non - exercise group . *
significantly different compared with cg ( p<0.05 ) ; significantly different 
 compared with ng ( p<0.05 ) the np - probnp levels differed significantly between the groups : 27.8  8.7  pg / ml for the 
 control group , 29.7  10.5  pg / ml for the high - intensity exercise group , 38.5  12.8  pg / ml 
 for the moderate - intensity exercise group , and 58.5  15.3  pg / ml for the non - exercise group 
 ( p<0.05 ) .
the post hoc analysis showed that the non - exercise group had significantly 
 higher np - probnp levels than the control group ( p<0.05 ) , and the high- and 
 moderate - intensity exercise groups had significantly lower np - probnp levels than the 
 non - exercise group ( p<0 0.05 ) ( table 1 ) .
this study examined the impact of four weeks of moderate- and high - intensity treadmill 
 warming - up exercise on the heart s condition during serious aerobic exercise using a sample 
 of sprague - dawley white male rats . in this study results , the blood ctni levels of the non - exercise group and the 
 moderate - intensity training group increased significantly after long - distance running 
 compared to the control group , which did not perform long - distance running .
however , the 
 high - intensity training group did not show a significant increase , indicating that 
 high - intensity training in advance of long - distance running is effective at preventing 
 myocardial damage during long - distance running .
this result is consistent with the results 
 of a study by chen et al.9 , in which ctnt 
 concentrations in white rats decreased remarkably in an experiment group that performed 
 high - intensity warm - up swimming training with an extra weight compared with an experiment 
 group that swam without a weight . the study argued that performing preliminary exercise 
 before high - intensity training can decrease myocardial damage or negative impacts in the 
 body in case of fierce exercise . in the current study ,
a significant increase in nt - probnp , 
 which is used as an indicator of cardiac insufficiency , was observed in the nonexercise 
 group .
several studies reported that elite athletes , non - elite athletes , and leisure players can 
 show a short - term increase in nt - probnp after intense and severe long - term exercise . 

moreover , nt - probnp concentration increases after long - term exercise or fierce endurance 
 exercise10 , 11 .
however , nt - probnp concentrations at rest do not increase among 
 trained athletes compared to untrained people in the same age group10 , 12 . in the current study ,
the moderate- and high - intensity exercise groups showed a significant 
 decrease of indicator for myocardial damage compared to the non - exercise group when 
 implementing serious long - distance running . among the exercise groups ,
the prevention 
 effects were larger the high - intensity training than the moderate - intensity training .
this 
 implies that performing high - intensity training before severe aerobic exercise is effective 
 at preventing myocardial damage .
wannamethee et al.13 noted that the implementation of regular exercise reduced 
 exercise - induced inflammatory responses ; this was attributed to adaptive responses to the 
 exercise and to anti - inflammatory effects .
the current study found that , compared to the nonexercise group , rats that underwent 
 preceding exercise showed less cardiac muscle damage and inflammatory responses during 
 prolonged intense exercise . in particular , the effects were greater after one bout of 
 intense exercise following high - intensity training than moderate - intensity training .
 [ purpose ] the purpose of this study was to investigate the effects of exercise on 
 myocardial injury in male sprague - dawley rats . 
 two groups of rats were trained with either 
 moderate- or high - intensity treadmill running for four weeks . 
 subsequently , the 
 concentrations of cardiac troponin and the n - terminal of prohormone brain natriuretic 
 peptide ( nt - probnp ) were examined following a single bout of prolonged intensive exercise 
 ( lasting 3 h ) . [ subjects and methods ] the study included 40 six - week - old male 
 sprague - dawley rats weighing 150180  g each . 
 the aerobic exercise group was divided into 
 high - intensity ( 28 m / min ) and moderate - intensity ( 15 m / min ) subgroups . 
 both subgroups were 
 trained for 35  min daily for six days per week ( excluding sunday ) over a four - week period . 
 following training , the high- and moderate - intensity exercise groups and a nonexercise 
 group performed one bout of prolonged treadmill exercise for 3  h at a speed of 15 m / min . 
 [ results ] the cardiac troponin and nt - probnp levels differed significantly between the 
 groups . 
 [ conclusion ] the exercise groups showed lower levels of cardiac troponin and 
 nt - probnp than the nonexercise group after the bout of prolonged intensive exercise . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION