post activation potentiation ( pap ) is a method used to increase the explosive strength of a 
 contractile activity in order to naturally increase physical capabilities in the acute 
 phase1 .
the stimulus results in two 
 opposing outcomes : on the one hand , there is atp level depletion post - workout ; and , on the 
 other hand , there is an activation of the central nervous system that lasts a few seconds in 
 the motor endplate ( this time has not been defined nor standardized ) .
the presence of both 
 of these factors leads to a pap of the stimulated musculature1,2,3,4 , provided that the recovery 
 is faster than the dissipation of the neuronal transmission .
there are a number of researchers who have tried to increase the explosive strength and 
 velocity by generating pap through different activation methods5,6,7,8 .
for example , maio alves et 
 al.6 obtained a significant velocity 
 increase with 8 weeks of training .
it is worth mentioning that all the studies consulted for 
 this article are based on the principle explained by sale1 for the generation of pap .
all of these studies used constant 
 resistance as activation ; therefore , there is not enough evidence to support the notion that 
 the basic principles of pap can be obtained with a complex training protocol .
several of the authors mentioned in this article researched the pap effect with constant 
 resistance9 , 10 , but there is no conclusive evidence about the changes in explosive 
 strength due to pap when the activation is induced by complex training .
it seems that a 
 valid alternative in sports training is to know the behavior of the reflex elastic explosive 
 strength in power zones ( from 0.6 to 0.9 m / s of velocity in bar squats ) , and how this 
 strength increases due to pap in the muscles involved in 30-m sprints .
simultaneously , it is 
 fundamental to determine how the power levels are modified during squats by extra load 
 applied in order to meet the aim of the study , since diminishing the power would decrease 
 the pap effect .
the main aim of the study was to determine the acute temporal effect of complex training 
 with squats on 30-m sprint times . as a secondary aim ,
these indicators show the variation of the average power and the maximum 
 power of the squat during complex training .
developing exercises with elite athletes is a privilege only a few researchers have ; 
 however , doing so presents a few methodological issues .
it is common for elite athletes to 
 be a very small sample ; fortunately , there are experimental designs that facilitate such 
 work with reduced and specific samples . using the same subjects in a controlled condition 
 and
the experimental condition is one of the most widely - used strategies in research 
 involving people .
seven male subjects participated in this study . a quasi - experimental intra 
 subject design was used together with a control condition and an experimental condition ; 
 both of the latter two conditions were conducted 48 hours apart . before any intervention
, 
 all the subjects were measured for their weight , and size and thickness of their skinfold . 

all the subjects of the study were requested to restrain from ingesting caffeine , drugs , or 
 any substance that could increase their metabolism during the course of the experiment .
seven male military athletes of the chilean navy ( age : 25.0  2.6  years ; weight : 67.1  2.0 
 kg ; height 172.7  3.6  cm , body mass index : 22.5  1.0  kg / m2 ; body fat percentage : 12.0  
 2.6% ) ( table 1table 1.characteristics of the sample ( means  sd)experimental group ( n=7)age ( years ) 25.0  2.6height ( cm)172.7  3.6weight ( kg)67.1  2.0bmi ( kg / m)22.5  1.0fat percentage12.0  2.6bmi : body mass index ; sd : standard deviation ) were enrolled in the study .
each athlete and their coach was informed about 
 the aim of the study and the possible risks of the experiment , and they all signed a consent 
 form before participating in the study .
the signed consent form and the study were approved 
 by the research ethics committee of universidad de granada , spain ( register n 933 ) .
bmi : body mass index ; sd : standard deviation for the characterization of the sample , weight and height were measured with a health o 
 meter professional scale and stadiometer .
the skinfolds of the biceps , triceps , 
 subscapularis , and supraspinatus were measured to determine the fat percentage .
standard warm - up : for the evaluation of one repetition maximum ( 1rm ) , the control set , and 
 the treatment based on complex training , the standard warm - up consisted of a 10-minute jog . 
 during the first 5 minutes
, subjects performed a low - intensity run and in the next 5 minutes 
 they added some ballistic movements to the lower limbs ( hip adductions , abductions , flexion 
 and extension , and knee and ankle flexion and extension ) .
base line : for the evaluation of 1rm , encoder lineal chrono jump and chronojump 
 version 1.4.6.0 software were used .
the 1rm evaluation was performed indirectly 
 through the formula proposed by sanchez - medina et al12 .
twenty - four hours after the 1rm evaluation , a control set was 
 performed that consisted of 4 sets of 1rm 60% squats .
the aim of this was to verify the 
 vertical speed of the bar of each subject13 by determining the peak power and average power of squats . 

furthermore , three 30-m sprint sets were evaluated using a chrono jump photocell 
 and the chronojump version 1.4.6.0 software .
the times were measured at the 
 starting point , and 10 m , 20 m , and 30  m. protocol : the intervention session with complex training consisted of : 4 sets of 5 
 repetitions of 30% 1rm + 4 repetitions of 30% 1rm + 3 repetitions of 30-meter sprint with 
 two - minute resets between repetitions of 30-meter sprint ( fig . 1afig .
1a.experimental protocol in complex training in squats1rm : 1 repetition maximum ; 30-m : 30 meters sprints and 1bfig .
1rm : 1 repetition maximum ; 30-m : 30 meters sprints ; s : seconds ; r1 : first repetition 
 of 30-m ; r2 : second repetition of 30-m ; r3 : third repetition of 30-m ; w : watts ) .
experimental protocol in complex training in squats 1rm : 1 repetition maximum ; 30-m : 30 meters sprints design of experimental protocol with complex training .
1rm : 1 repetition maximum ; 30-m : 30 meters sprints ; s : seconds ; r1 : first repetition 
 of 30-m ; r2 : second repetition of 30-m ; r3 : third repetition of 30-m ; w : watts during the protocol of complex training with squats , the vertical velocity of the bar in 
 the low intensity ( 30% 1rm ) and high intensity ( 60% 1rm ) tasks in each set was monitored . 

also , 
 all 30-meter sprint repetitions were evaluated ( 3 repetitions per set ) in order to determine 
 the appearance of pap ( fig .
sequence of 30-m sprint repetition in experimental protocol the minimum times of the 30-meter sprints ( 10 m , 20  m and 30 m ) , and average power and peak 
 power were submitted to the kolmogorov - smirnov ( k - s ) test .
repeated measures anova test was 
 used to analyze the differences among the control sets and the four complex training sets . 

the effect size for this analysis was calculated using the partial eta - squared test . for post hoc analysis ,
student s t - test was conducted on those variables that showed 
 significant differences in the repeated measures anova test .
the following comparisons were 
 carried out using student s t - test : control sets vs. experimental set 1 ( pair 1 ) , control 
 set vs. experimental set 2 ( pair 2 ) , control set vs. experimental set 3 ( pair 3 ) , and 
 control set vs. experimental set 4 ( pair 4 ) .
the size of the effect for this analysis was 
 calculated using cohen s d test with the following effect scale : insignificant ( d < 0.2 ) , 
 small ( d = 0.2  0.6 ) , moderate ( d = 0 .
 1.2 ) , large ( d = 1.2  2.0 ) , and very large ( d 
 > 2.0 ) .
according to anova , the partial times of the 10-meter and 20-meter sprints did not show any 
 significant differences between the control set and the 4 experimental sets ( p = 0.46 and p 
 = 8.80 ) .
however , was there a significant decrease in the 30-meter time 
 between the control set and the 4 experimental sets ( p = 0.0001 ) .
the decrease in the minimum time of the 30-meter sprint was attributed to pap in the lower 
 limb muscles activated by the complex training .
the control set and the 4 experimental set 
 results are shown in table 2table 2.results ( means [ sd ] ) of post activation potentiation ( pap ) elicited by complex 
 training with squats for the control set and the four experimental setsvariables control setset 1set 2set 3set 4means ( sd)means ( sd)means ( sd)means ( sd)means ( sd)time in 10 m ( s)1.680.081.660.121.670.101.680.121.710.12time in 20 m ( s)3.000.142.970.163.010.162.990.173.010.16time in 30 m ( s)**4.570.234.220.204.270.204.230.234.230.21average power ( w)579.2133.2592.4110.0587.8115.6584.4144.5625.4143.9peak power ( w)1,451.2216.11,368.5176.71,451.3210.21,424.5279.11,451.2285.7sd : standard deviation ; * * p<0.0001 .
sd : standard deviation ; * * p<0.0001 the average power and peak power of squats did not show any significant changes between the 
 control set and the 4 experimental sets ( p = 0.52 and p = 0.45 ) .
hoc analysis , the control set and the 4 experimental sets were examined in pairs . 

the results of student s t - test for 
 all 4 pairs of results are shown in table 
 3table 3.post hoc analysis of 30-m sprint times after post activation potentiation ( pap ) 
 elicited by complex training :
control set vs. the four experimental setscontrast among conditions(control set  sets ) control setsetsmeans ( sd)means ( sd)pair 1time ( s)*control set set 14.570.234.220.20pair 2time ( s)*control setset 24.570.234.270.20pair 3time ( s)*control setset 34.570.234.230.23pair 4time ( s)*control setset 44.570.234.230.21 : seconds ; sd : standard deviation ; * p<0.01 . : seconds ; sd : standard deviation ; * p<0.01
regarding the first aim of the study , the results of anova showed a positive temporal acute 
 effect of complex training in 30-meter sprints performed by military athletes .
this positive 
 effect was a consequence of pap in the muscles used in the sprint , as a result of higher 
 phosphorylation of the light chains of muscular miosine1 .
it is also important to mention that in the post hoc analysis , the 
 size of the effect in the student s t - test was large in all the pairs evaluated .
similar to 
 this study , okuno et al.7 researched pap 
 conducting complex training for the lower limbs , and found a significant increase in the 
 sprint velocity in the repeated sprint ability ( rsa ) test ( p = 0.01 ) ( 30 meters with a 
 change of direction at 15 meters ) .
however , lim et al.14 did not find any significant differences among the 10-m , 20-m , and 
 30-m sprint times .
possibly , the weight increase ( load ) used in the present study elicited pap in the 30-meter 
 sprint muscles , since both this study and the study performed by okuno et al.7 used complex training with squats as an 
 activation method . in the literature , there are several studies which investigated the chronic effect of 
 complex training on pap over different sprint distances5 , 15,16,17 , but only a few studies 
 have demonstrated significant changes in sprint time and velocity over 30 m5 , and/or demonstrated a positive correlation 
 between explosive force tests ( squat jump ) versus sprints17 .
similarly , pap was only elicited acutely in those cases where 
 complex training was conducted . in the studies where constant resistance was applied , the 
 variables measured showed no significant changes9 , 
 16 .
it seems that working with constant 
 resistance causes the neuromuscular system to stabilize , limiting pap and , in consequence , 
 explosive strength events .
in contrast , complex training activates the neural system , but 
 does not trigger fatigue in athletes .
the combination of both processes generates pap and an 
 increase in the explosive strength , and in this study , it generated a better performance in 
 30-m sprints .
regarding the second aim of the study , the anova results show there were no significant 
 changes in the peak power and average power of squats ( p = 0.45 ; p = 0.53 ) .
similar to this 
 study , marques et al.18 reported the bar 
 velocity , peak power , and average power of throwing a handball ; however , these researchers 
 did not evaluate pap as a study variable .
walker et al.19 observed the chronic effects of complex training on pap and the 
 fatigue index , and found a substantial increase in the active strength ( p<0.05 ) , as well 
 as a substantial increase in the muscular fatigue after the activation ( p<0.05 ) .
the 
 evidence shows that long - term workouts increase the fatigue index , but there is no 
 conclusive evidence to support the generation of neuromuscular fatigue with complex training 
 of 60% 1rm , since this study pap in 30-meter sprints .
if athletes had experienced fatigue , 
 it is likely that they would not have shown potentiation1 , 2 , 20 , 21 .
the present results shown indicate that complex training activation elicits pap as 
 evidenced by the 30-meter sprint of military athletes .
this pap is clearly seen in the 
 significant decrease in the minimum times of the 30-meter sprints , and the lack of variation 
 in the peak power and average power of the control set and the 4 experimental sets . 

therefore , working with 4 sets of 5 repetitions of 30% 1rm + 4 repetitions of 60% 1rm + 3 
 repetitions of 30-meter sprints with a 120-second rest , seems to be a valid way of 
 developing explosive strength in the lower limbs . from a practical point of view , the application of complex training for physical capacity 
 is a good method of increasing explosive strength levels in the lower limbs , since it 
 stimulates two physical capacities simultaneously , increasing both muscular strength in the 
 back squat series and explosive strength in 30-m sprints .
it is our suggestion that complex 
 training should be performed with load in power zones ( from 0.6 to 0.9 m / s of velocity in 
 bar squats ) in the pre - competition and competition phases , since it stimulates the central 
 nervous system without causing fatigue in the muscles used in the 30-m sprint .
finally , it 
 is our suggestion that all movements , either back squats or 30-m sprints , should be executed 
 at the fastest speed of movement possible .
 [ purpose ] the aim of this study was to determine the acute effect temporal of a complex 
 training protocol on 30 meter sprint times . 
 a secondary objective was to evaluate the 
 fatigue indexes of military athletes . 
 [ subjects and methods ] seven military athletes were 
 the subjects of this study . 
 the variables measured were times in 30-meter sprint , and 
 average power and peak power of squats . 
 the intervention session with complex training 
 consisted of 4 sets of 5 repetitions at 30% 1rm + 4 repetitions at 60% 1rm + 3 repetitions 
 of 30 meters with 120-second rests . for the statistical analysis repeated 
 measures of 
 anova was used , and for the post hoc analysis , student s t - test was used . 
 [ results ] times 
 in 30 meter sprints showed a significant reduction between the control set and the four 
 experimental sets , but the average power and peak power of squats did not show significant 
 changes . [ conclusion ] 
 the results of the study show the acute positive effect of complex 
 training , over time , in 30-meter sprint by military athletes . 
 this effect is due to the 
 post activation potentiation of the lower limbs muscles in the 30 meters sprint . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION