muscle damage and delayed onset muscle soreness ( doms ) may occur at different levels 
 depending on the type of contraction ( concentric or eccentric ) , type of exercise ( plyometric 
 jumps , resistance training , downhill runs , long - term runs , etc . ) , movement speed ( high or 
 low angular velocity ) , time interval between sets , and trainability of the individual 
 ( sedentary , physically active , or trained)1 . for a given muscle power
, it is known that there is less 
 recruitment of motor units for eccentric contraction than for concentric contraction2 .
this higher strength / activation ratio 
 exerts high stress on the tissues involved , and is considered the main factor in structural 
 damage of muscle fibers .
additionally , the connective tissue is stretched , causing greater 
 passive strain on the cytoskeleton .
these two factors together are responsible for a higher 
 incidence of muscle damage and consequent reduction in contractile capacity , also known as 
 fatigue3 .
it has recently been postulated that muscle damage caused by eccentric or any other 
 physical activity may be minimized by performing the same type of exercise a few weeks after 
 the initial training .
the protective mechanism of the repeated 
 bout effect appears to be due to an increase in the recruitment of slow contraction motor 
 units , activation of a large number of motor units ( neural adaptation ) , increased dynamic 
 and passive muscular endurance ( mechanical adaptation ) , longitudinal addition of sarcomeres , 
 adaptation to the inflammatory response , and adaptation to maintain muscle 
 excitation - contraction coupling ( cellular adaptation)5 . however , most studies that investigated the repeated bout effect observed a decrease in the 
 ability of muscle to generate strength and power .
few studies have verified the repeated 
 bout effect or the effect of repetition of eccentric exercise on subsequent aerobic 
 performance .
previous articles reported that both oxygen consumption kinetics and running 
 economy are negatively affected when a prior eccentric exercise is performed6 , 7 .
therefore , the present study aimed to evaluate the influence of repeated bouts of eccentric 
 exercise on subsequent high - intensity aerobic performance .
it is believed that severe 
 neuromuscular fatigue develops after eccentric high - intensity exercise .
however , an analysis 
 of the literature suggests that the harmful effects may be minimized by performing the same 
 activity several weeks later , which could induce favorable adjustments to offset these 
 effects on subsequent aerobic performance .
the subject population was a convenience sample comprised of 7 healthy male volunteers , 
 sedentary for at least 3 months , and with no experience in resistance training .
demographic 
 data for the sample were as follows ( mean  standard deviation [ sd ] ) : age ( 21.7  
 3.4  years ) ; body mass ( 67.2  9.9  kg ) ; height ( 171.5  0.0  cm ) ; fat percentage ( 15.4  7.1% ) 
 and maximum oxygen consumption ( 44.1  2.8  mlkgmin ) .
each 
 volunteer was informed about the investigational procedures and their implications , and 
 provided signed informed consent to take part in the study .
the study was approved by the 
 human research ethics committee of unisalesiano , protocol number : 292/09 .
anthropometric data included body mass ( bm ) , 
 height ( h ) , and the percentage of body fat from skinfold measurements8 . subjects performed incremental treadmill testing until 
 volitional exhaustion to determine vo2max and the intensity associated with the 
 achievement of vo2max ( vvo2max ) .
this test started at 
 8  kmh , with increases of 1  kmh at each stage . using a 
 metabolic analyzer ( cortex metalyser 3b , leipzig , germany ) , each subject was 
 encouraged to give maximum effort .
the test completion was determined by volitional 
 exhaustion or when one of the following criteria was reached9 : ( 1 ) peak heart rate ( hr ) at least equal to 90% of the age - predicted 
 maximum ; ( 2 ) respiratory exchange ratio ( rer ) greater than 1.1 ; and ( 3 ) increased intensity 
 with stable oxygen consumption .
the vo2max was defined by the higher average 
 value of oxygen consumption ( vo2 ) found during the last 30  s of each stage .
the subjects 
 returned to the laboratory the following week to determine the time limit to 
 vvo2max ( tlim control ) , which was characterized by treadmill running at 
 vvo2max until voluntary exhaustion ; the hr and lactate concentration ( yellow 
 springs 1500 sport , ohio , usa ) were measured before and after tlim .
a plyometric activity was performed in the third week , consisting of 10 sets of 10 depth 
 jumps , with a 1-min interval between each set , in which subjects jumped from a high level 
 ( 0.6 m ) .
after landing , the subjects were asked to perform the strongest possible vertical 
 jump , to land on another higher plane placed 1  m in front of the first .
after 15  min , they performed another time limit activity ( tlim 
 1 ) .
after 6 weeks of limited physical activity , volunteers returned to the laboratory to 
 perform the same procedures as in the third week , with a plyometric activity followed by 
 treadmill running at vvo2max ( tlim 2 ) . for at least 24  h before the experiments , 

volunteers were advised to avoid any strenuous physical activity and alcoholic or 
 caffeinated drinks , with a night of proper rest and the last meal at least 2  h prior to the 
 test . to avoid any effects of a circadian cycle ,
all procedures were performed during the 
 same period and time of day for each subject .
statistical analysis was performed using spss version 20.0 ( chicago , il , usa ) prior to any 
 analysis , a shapiro - wilk normality test was applied . before the confirmation of normality , 
 one - way analysis of variance ( anova ) was applied with a post - hoc tukey test to compare data 
 for tlim ( control , 1 , and 2 ) and physiological variables related to performance times ( blood 
 lactate and hr ) .
student s t - test was used for paired data for the same physiological 
 variables before and after the plyometric activity . in all analyses , a significance level of 
 p0.05 was adopted .
table 1table 1.characteristics of volunteersmeansdage ( years)21.73.4body weight ( kg)67.29.9height ( cm)171.50.0fat percentage ( % ) 15.47.1vo2max 
 ( mlkgmin)44.12.8vvo2max ( kmh)12.71.7vo2max : maximum oxygen uptake ; vvo2max : speed associated with 
 maximum oxygen uptake shows the initial data of the sample , including the cardiorespiratory 
 variables ( vo2max and vvo2max ) related to the initial level of 
 physical fitness , as an inclusion criterion .
vo2max : maximum oxygen uptake ; vvo2max : speed associated with 
 maximum oxygen uptake table 2table 2.permanence time at vvo2max in control situations ( tlim control ) and 
 after the first and second session of depth jumps ( tlim 1 and tlim 2)tlim control ( s.)tlim 1 ( s.)tlim 2 ( s.)mean283.4125.2192.7sd47.764.171.9significant difference from tlim control ; p<0.05 shows tlim ( control , 1 , and 2 ) .
there was a significant difference between 
 tlim 1 and tlim control , suggesting the deleterious effect of previous eccentric exercise
. 
 however , after 6 weeks of limited activity , tlim control and tlim 2 showed no statistically 
 significant differences , demonstrating the repeated bout effect on subsequent aerobic 
 performance . significant difference from tlim control ; p<0.05 tables 3 and 4table 3.mean values and standard deviation ( sd ) of physiological responses ( blood lactate 
 concentrations [lac ] , and maximum heart rate hrmax ) after tlimmeansd[lac ] tlim control ( mmol / l)11.684.43[lac ] tlim 1 ( mmol / l)9.083.75[lac ] tlim 2 ( mmol / l)9.843.38hrmax tlim control ( bpm)198.410.6hrmax tlim 1 ( bpm)192.212.6hrmax tlim 2 ( bpm)198.110.6 show the hr and concentrations of lactate after tlim and following the depth 
 jumps , respectively . table 3 shows no 
 statistically significant differences for the 2 variables after 3 time limits . table 4table 4.mean values and standard deviation ( sd ) of physiological responses ( blood lactate 
 concentrations [lac ] , and maximum heart rate hrmax ) after the depth jump 
 ( dj)meansd[lac ] jd 1 ( mmol / l)7.573.21[lac ] jd 2 ( mmol / l)5.912.36hrmax jd 1 ( bpm)177.87.1hrmax jd 2 ( bpm)178.010.3 shows the same results after depth jumps .
the purpose of this research was to investigate the influence of the repeated bout effect 
 of eccentric exercise on subsequent high - intensity aerobic performance .
the primary finding 
 was that eccentric exercise decreases aerobic performance after the first time limit , but 
 deleterious effects are minimized after performing the same exercises ( jumps ) a few weeks 
 later .
this adaptation is called the  repeated bout effect11 , 12 . in the current study ,
thus , one of the criteria used to determine the cardiorespiratory level of 
 subjects was obtained in an incremental ergometry test .
thus , the volunteers were considered sedentary , because of their 
 average values for vo2max ( 44  ml / kg / min ) . according to the present investigation and previous studies that also used depth jump 
 exercises to generate muscle damage , low ( 10 jumps ) and high volumes ( 4550 jumps ) , provided 
 the same protective effect against muscle damage induced by the first exposure .
however , a 
 larger volume of eccentric movements induces muscle damage as compared to a lower 
 volume5 , 14 .
muscle damage is closely related to decreased muscle contractile 
 capacity ; in physiological terms , the greater the damage , the greater the muscle 
 fatigue15 . the protective mechanism of the repeated bout effect appears to be due to an increase in 
 the recruitment of slow contraction motor units , activation of a large number of motor units 
 ( neural adaptation ) , increased dynamic and passive muscular endurance ( mechanical 
 adjustments ) , longitudinal addition of sarcomeres , adaptation to the inflammatory response , 
 and adaptation to maintain muscle excitation - contraction coupling ( cellular adaptation)5 , 14 . 

however , there is little information about the repeated bout effect of eccentric exercise on 
 subsequent aerobic performance .
the effect of repeated bouts of eccentric exercise on 
 running economy16 , 17 and vo2 kinetics during cycloergometric exercise 
 performance7 was verified by some 
 authors .
the effect of eccentric exercise on running economy seems to be intensity 
 dependent ; at moderate intensities ( 5575% of vo2max ) , running economy is not 
 affected , but is only influenced at high intensities ( up to 90% of vo2max ) .
this 
 is due to prior fatigue of type ii fibers that are additionally recruited at high aerobic 
 exercise intensities18 .
moreover , byrne , twist , and eston19 
 reported that the performance of eccentric exercise at high intensity prior to aerobic 
 activities can lead to reduction in contractile ability of the quadriceps muscles and 
 reduced muscle force development ratio ( fatigue ) , thus increasing the contact time with the 
 ground during running and decreasing efficiency of the exercise . according to billat et 
 al.20 ,
the determination of 
 vvo2max is dependent on factors that are not related solely to anaerobic 
 participation in the aerobic component , especially with regard to the slow component of 
 oxygen uptake kinetics .
eccentric exercise performed prior to aerobic exercise decreases the 
 recruitment level of type ii fibers , thus decreasing the amplitude of the slow component in 
 determining vo2max , and interfering with the time to exhaustion at 
 vvo2max20 , 21 .
thus , the adaptations to the repetition of exercise cited by miyama and nosaka5 can improve the level of muscle fiber 
 recruitment after the performance of the second eccentric exercise , which could explain the 
 statistically similar times between tlim control and tlim 2 .
for the limit time exercise at 
 vvo2max ( tlim control , tlim 1 and tlim 2 ) , and the depth jump performed by the 
 volunteers , physiologic stress apparently was no different between the moments before and 
 after six weeks without exercise , since the hr values and lactate concentrations were 
 statistically similar .
however , the lactate concentrations after tlim 1 and tlim 2 tended to 
 be lower than in tlim control .
this lower concentration can be explained by lower lactate 
 removal capacity after exercises with high - intensity eccentric contractions22 .
thus , it can be concluded that the  repeated bout effect  exerts a positive influence on 
 vvo2max , possibly resulting in less deleterious effects on the permanence time 
 after 6 weeks of limited physical activity .
however , methodological limitations of this 
 study suggest the need for further research . due to the great variability of the tlim , a 
 larger sample would increase the statistical power .
in addition , the kinetic measurement of 
 oxygen uptake , and even electromyographic evaluation of the muscles involved , could help 
 explain the repeated bout effect on subsequent high - intensity aerobic activity , as well as 
 variables related to muscle damage ; these findings could help explain the damage caused by 
 eccentric high - intensity activities .
 [ purpose ] it is believed that eccentric high - intensity exercise can decrease performance 
 in subsequent exercise . however , with repetition , the deleterious effects can be 
 minimized . 
 thus , this study evaluated the influence of repeated bouts of eccentric 
 exercise on subsequent high - intensity aerobic performance . 
 [ subjects and methods ] seven 
 healthy and sedentary male volunteers were recruited . 
 a ) visit 1 : determination of maximum 
 oxygen uptake ( vo2max ) and speed associated with maximum oxygen uptake 
 ( vvo2max ) in incremental treadmill testing ; b ) visit 2 : run to exhaustion at 
 vvo2max ( tlim control ) ; c ) visit 3 : 10 sets of 10 depth jumps , followed by a 
 run to exhaustion at vvo2max ( tlim 1 ) ; d ) visit 4 : after 6 weeks without any 
 physical training , the volunteers carried out the same procedures as on the third visit 
 ( tlim 2 ) . 
 data were analyzed using one - way analysis of variance ( anova ) with the post - hoc 
 tukey test . 
 [ results ] significant differences were found between tlim control and tlim 1 
 ( 283.4  47.7  s vs. 125.2  64.1  s , respectively ) , these were not different from tlim 2 . 
 
 [ conclusion ] eccentric exercise showed deleterious effects on subsequent high - intensity 
 aerobic performance . 
 these effects were minimized after the exercise protocol was repeated 
 6 weeks after the first event . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION