eccentric exercise was shown to provoke skeletal muscle damage leading to delayed onset of 
 muscle soreness ( doms)1,2,3 .
acute muscle damage can 
 cause discomfort at the site of injury , inflammation , oxidative stress , edema , and loss of 
 muscular function and strength4 , 5 .
many researchers have attempted to ameliorate symptoms by 
 various treatments , such as nutritional interventions3 , 6 , pharmacological 
 interventions7 , massage8,9,10 , low - intensity exercise10 , ultrasound application11 , or cryotherapy12 . even though some positive effects have been reported
, 
 several studies did not find any reductions in the symptoms of muscle injuries . beside these treatments ,
static or pulsed electromagnetic field therapy have been used for 
 the treatment of doms13,14,15 .
again , some 
 authors reported positive effects on doms symptoms , whereas others were not able to find 
 benefits13 , 14 .
application of a pulsating electrostatic field ( pesf ) , which is a 
 comparable but not identical technique , might be a further method capable of reducing the 
 symptoms of muscle soreness .
a pesf was shown to increase vasomotion and as a consequence 
 blood flow16 , to reduce the formation of 
 rouleaux , and to increase metabolic activity16 , 17 .
furthermore , a pesf may function as an 
 ion pump able to move calcium ions , the concentration of which was shown to be increased 
 after eccentric exercise with detrimental effects2 , 
 18 .
due to these effects , it might be 
 speculated that a pesf could prevent the development of doms and muscle strength loss after 
 muscle damaging exercise .
therefore , the aim of the present study was to investigate the 
 effect of pesf application on sensation of muscle soreness and muscle strength after 
 eccentric exercise .
nine sport students ( 5 males , 4 females ) without any medical problems and not adapted to 
 eccentric exercise were recruited for the study .
all of them were informed about the study 
 aims and gave written informed consent for participation .
two participants ( one male and one 
 female ) had to be excluded from the final analysis , one because of a pre - start muscle 
 soreness score of already 4 and one because of a pre - start ck value of 333 u / l . therefore , 7 
 participants ( 4 males and 3 females ; weight , height , and age : 74.35.7  kg and 71.05.3  kg , 
 183.09.9  cm and 172.36.4  cm , and 26.52.4  years and 24.31.2  years , respectively ) were 
 included in the final analysis .
the study was carried out in conformity with the ethical 
 standards of the declaration of helsinki and was approved by institutional review board of 
 the department of sport science , university of innsbruck .
the study was designed as a single - blinded , placebo - controlled cross - over intervention 
 study .
all participants performed 2 downhill running sessions on a treadmill separated by at 
 least 4 weeks . before and at different time points after the sessions
, muscle soreness 
 score , creatine kinase ( ck ) , and jump ability were assessed as described in detail below . 

the first running session was carried out in a slightly modified form according to kingsley 
 et al5 .
running sessions started with a 
 3  min stage of horizontal running at 5  km / h ( warm - up ) .
thereafter , the inclination was set 
 at 17.5% , and the speed was increased every minute by 1  km / h until reaching approximately 
 70% of the age - predicted maximal heart rate ( hr ) ( calculated as 220  age ) .
overall , the running duration was 30 
 minutes , not including the warm - up time . during the second test
, the speed was regulated in 
 the same way as during test one but independent of hr in order to have identical test speeds 
 and a comparable muscular stimulus . immediately after each run ,
half of the subjects were 
 treated in a sitting position with a pesf for 45  min , and half of the subjects were exposed 
 to a sham treatment .
after at least 4 weeks , in which participants were advised not to 
 change their physical activity habits , the subjects that were treated with a pesf during the 
 first session received the sham treatment and those that were treated with the sham 
 treatment during the first session received the pesf treatment .
the ( negative ) pesf was generated with a new health 
 9000 device ( akern srl , pontassieve , italy ) and was applied through a mat with a field 
 intensity of 9000 v , a current of < 9 ma , and a pulsatile frequency of 50  hz . the 
 electrostatic field was confined to the ion mat surface , and it has been proven to be 
 safe17 .
the general rating of muscle soreness was assessed as described by trombold et al.3 before and immediately after the runs , 
 immediately after the 45  min treatment or sham treatment , and 48 hours after treatment . 

participants subjectively rated the degree of soreness using a visual analog scale of 0 to 
 10 , with 0 describing  no soreness  and 10 describing  unbearable soreness  . jump ability 
 ( jump and reach test ) was assessed before running , after the 45  min session , and 48 hours 
 after the running .
ck activity was assessed before running and 48 hours after running from 
 capillary blood samples with a reflotron sprint device ( reflotron sprint , mannheim , germany ; 
 reference range for men : 24195 u / l at a measurement temperature of 37  c ) .
delta values (  ) were calculated as post values 
 ( at different time points ) minus pre values for both the pesf application and sham setting . 

differences at baseline , changes in the course of pesf or sham treatment , and differences 
 between conditions (  values for the pesf and sham treatment ) were assessed by paired 
 student s t - tests or the wilcoxon test as appropriate .
spearman correlation analyses were 
 used to calculate associations between ck and cmj changes and muscle soreness score .
when compared with the pre 
 values , the muscle soreness score was increased at all time points and under both conditions 
 ( p<0.05 ) .
jump performance was reduced immediately after the sham application ( p=0.038 ) 
 and tended to be reduced immediately after the pesf application ( p=0.054 ) . table 1table 1.values for jump height , creatine kinase , and muscle soreness score in the courses 
 of the pesf and sham treatmentspreafterrunafter45 min 24 hafter48 hafterjump and reach ( cm)pesf276.28.7273.07.03.33.9273.010.53.33.6sham276.521.6272.023.54.55.3272.023.24.56.2creatine kinase ( u / l)pesf133.632.1171.971.338.358.7sham100.141.0271.7274.5171.6285.8muscle soreness scorepesf1.41.43.61.72.12.04.02.02.61.65.10.93.71.64.61.53.12.0sham1.01.04.01.43.01.74.11.73.12.26.71.75.72.26.42.45.43.2pesf : pulsating electrostatic field . the table represents values of the same 
 participants receiving the pesf and sham treatments ( n=7 , crossover design ) . 
 
there was a trend toward significant differences in delta values (  = 
 after values ( i.e. 45  min , 24 h , and 48  h after ) minus pre value ) between treatments 
 ( pesf vs. sham ) . shows values for ck , muscle soreness score , and jump height in the courses of 
 the pesf and sham treatments .
twenty - four and 48 hours after downhill running , the muscle 
 soreness score ( mss ) tended to be less after pesf administration when compared with the sham 
 treatment (  mss : 3.71.6 vs. 5.72.2 after 24  h and 3.12.0 vs. 5.43.2 after 48 h , 
 respectively ; 0.05<p<0.01 ) .
furthermore , the highest muscle soreness scores were found 
 after the sham session , with one subject having a score of 9 and two subjects having a score 
 of 8 after 24 hours .
after 48 h , one subject had a score of 10 , one subject had a score of 
 9 , and one subject had a score of 7 .
after 48 hours , one subject had a score of 7 , whereas all others had 
 lower values .
the table represents values of the same 
 participants receiving the pesf and sham treatments ( n=7 , crossover design ) . 
 
there was a trend toward significant differences in delta values (  = 
 after values ( i.e. 45  min , 24 h , and 48  h after ) minus pre value ) between treatments 
 ( pesf vs. sham ) .
the main finding of the present investigation was that pesf application tended to reduce 
 muscle soreness scores without significantly affecting ck increase and jump performance 
 decrease . to the best of our knowledge ,
this is the first study to use a pesf after downhill running 
 for the prevention of muscle soreness . in the literature , different methods , including cold 
 or infrared therapy , massage , pharmacological intervention , etc .
, have been applied to 
 reduce muscle pain after eccentric exercise7 , 8 , 10 , 12 .
the mechanisms causing beneficial effects 
 are as diverse as the methods applied . for cold application ,
the main beneficial effect is 
 thought to be the cold - related vasoconstriction , which may limit vessel permeability and 
 thus inflammatory processes12 .
the 
 mechanism by which infrared therapies might induce potential positive effects is mainly 
 based on the increased peripheral flow due to warmth - related vasodilatation , which could 
 enhance the evacuation of edema , limiting inflammation and perceived pain12 .
the mechanisms mediating the biological 
 benefits of nutritional interventions are not clear but may be linked to the attenuation of 
 oxidative stress and inflammation3 . with 
 respect to electromagnetic field therapy , it was suggested that the treatment influences 
 muscle immune and inflammatory responses by an unknown mechanism , may disrupt afferent input 
 from free nerve endings of nociceptors , and may influence excitation - contraction coupling 
 processes13 , 15 , 19 . in the present study
additionally , the improvement of 
 vasomotor performance might have provoked some beneficial effects16 , 17 .
comparable to 
 the effects of infrared application , the increased blood flow might have enhanced the 
 removal of edema , limited the inflammatory response , and reduced perception of pain12 . a further mechanism might be the function 
 of a pesf as an ion pump moving positively charged ions , e.g. , calcium and hydrogen16 .
the calcium concentration was shown to be 
 elevated in skeletal muscle cells following eccentric contractions18 . increased calcium concentrations within the sarcoplasm 

have the potential to activate many different molecular pathways in skeletal muscle , 
 including the phospholipase - prostaglandin pathway and the calpain proteolytic pathway , which 
 might lead to breakdown of the cell membrane and myofibrils2 . however , whether or not such mechanisms might be involved in 
 processes of recovery from exercise - induced muscle damage still needs to be determined .
it 
 has to be mentioned that although there was a trend toward a decrease in muscle soreness 
 score , ck and jump performance did not seem to be affected by pesf application . in this 

regard , the small sample size certainly is a main limitation of the present study and 
 outlines its nature as a pilot study . nonetheless ,
when looking at the mss and ck values in 
 table 1 , some beneficial effects clearly seem 
 to be apparent .
this is supported by the finding that the highest mss values were found 
 after the sham treatment .
additionally , pesf application for only 45  min may be considered a 
 short exposure time , and it is not known if a longer pesf application time would have been 
 more effective . in conclusion ,
application of a pesf might be a promising treatment to reduce muscle 
 soreness after exercise - induced muscle damage .
however , further studies are needed to 
 confirm the present outcomes and to establish the mechanism by which a pesf may reduce 
 muscle pain .
 [ purpose ] the aim of the study was to establish whether pulsating electrostatic field 
 application , shown to increase blood flow and metabolic activity and to function as an ion 
 pump , is able to reduce muscle pain after exercise - induced muscle damage . 
 [ subjects and 
 methods ] seven participants ( 4 males , 3 females ) performed two sessions of downhill 
 running separated by at least 4 weeks . 
 after the running sessions , participants were 
 either treated for 45  min with a pulsating electrostatic field ( field intensity , 9000 v ; 
 current , < 9 ma ; frequency , 50  hz ) or a sham treatment . 
 the order of the intervention 
 was random , and the condition was blinded for the participants . 
 muscle soreness score , 
 creatine kinase , and jump ability were assessed before and up to 48 hours after running . 
 
 [ results ] twenty - four and 48 hours after the downhill running , the muscle soreness score 
 tended to be less increased after pulsating electrostatic field administration when 
 compared with the sham setting ( changes in muscle soreness score : 3.71.6 vs. 5.72.2 
 after 24  h and 3.12.0 vs. 5.43.2 after 48 h , respectively ) . 
 no further differences were 
 detected . 
 [ conclusion ] the outcomes show that a pulsating electrostatic field might be a 
 promising treatment to reduce muscle soreness after exercise - induced muscle damage 
 . 
 however , further studies are needed to confirm the present outcomes and to establish the 
 mechanism by which a pulsating electrostatic field may reduce muscle pain . 