in the field of medicine ,  stress  is one of the most common complaints among patients1 .
stress may negatively influence the affective state of 
 an individual , which in turn may exert direct adverse effects on biological processes or 
 behavioral patterns , thereby increasing the individual s disease risk and pathogenesis of a 
 disease2 .
psychosocial stress is believed to contribute to musculoskeletal disorders of the neck , 
 shoulders , and other areas .
previous studies have shown that mental stress induces a 
 significant increase in muscle tension3 . 

recently , it has been demonstrated that the same motor units are activated by mental stress 
 as by physical stress , which means that mental stress may also result in low - threshold motor 
 units remaining active during breaks at work and outside of work3 .
thus , numerous therapeutic approaches have been used to 
 treat musculoskeletal diseases caused by psychological stress4,5,6 .
the utilization of alternative medicine has been increasing in recent years , with massage 
 documented as being one of the most frequently treatments for musculoskeletal disease7 .
manual lymph drainage ( mld ) is a procedure 
 that consists of several techniques derived from traditional massage8 .
mld has become increasingly popular in recent years , not 
 least because of the enormous amount of publicity it has recieved8,9,10,11,12 .
moreover , the spread of information about edema among doctors , 
 physical therapists , and patients , and the efforts for managing its cosmetic aspects have 
 also resulted in its popularity10,11,12 .
the frontal region of the brain has been associated with affective states , and different 
 affective states have been associated with different eeg patterns in this region13 .
normal subjects experience positively 
 valenced emotions , such as happiness and joy , together with greater relative left frontal 
 eeg activation . in contrast , the experience of negative emotions , including depression , is 
 associated with greater relative right frontal eeg activation14 , 15 .
there are some studies 
 that have investigated the effects of different manual techniques on frontal eeg 
 activation4 , 5 , 16 , 17 ; however , mld is not one of the techniques that have been 
 investigated .
therefore , the present preliminary study investigated the effects of mld in 
 subjects with psychological stress and greater relative right frontal eeg activation , with 
 mld expected to shift eeg patterns toward symmetry .
the subjects included 52 university students , chosen according to the following criteria : 
 ( 1 ) no history of mental illness , ( 2 ) not currently taking any medication known to affect 
 eeg signals , and ( 3 ) no known heart- or muscle - related disease .
they were all free of 
 pulmonary , cardiac , and metabolic disease , as well as other disease states , which may cause 
 brain dysfunction .
all subjects responded to the stress response questionnaire ( sri)18 and returned it to the authors . according 
 to the results of the questionnaire , 13 female subjects aged 19 to 23  years with an sri 
 score > 80 and
informed , 
 written consent was obtained from each subject after the experimental procedures had been 
 explained .
all test protocols were approved by the ethics committee of the physical therapy 
 faculty of kangwon national university .
all interventions 
 were completed in a supine position on a massage table with a pillow placed under the knees 
 to relax the lower back muscles .
data acquisition and mld were performed in a quiet , 
 temperature - controlled environment ( 2224  c ) .
stimuli such as conversation , phone calls , 
 and noise that could increase the activity of sentinel nodes were minimized , and the 
 subject s body was covered with a soft and thin sheet to avoid discomfort from body 
 exposure .
mld was conducted by a well - trained certified mld therapist , and applied twice to 
 the neck area .
the protocol was standardized , in that , the massage stroke category 
 ( type ) and time was the same for all participants .
subjects were allowed to rest comfortably for at least 5  min prior to the baseline 
 recording procedure .
eeg data were acquired for 5  min before , and immediately following , 
 mld .
a total of 6 channels of eeg were recorded : inclusive of fp1fp2 , f3f4 , and f7f8 . 

there were two other electrodes , a ground electrode and reference electrode , which were 
 placed on both zygomatic bones .
participants were then asked to close their eyes and refrain 
 from talking , falling asleep , or making exaggerated body movements , in order to observe the 
 cortical electrical activity without any external stimuli , minimizing possible visual 
 artifacts during eeg measurement .
the eeg signal was acquired over a 5-min period , followed 
 by computerized fourier analysis of the eeg waves using the telescan software package 
 ( laxtha , daejeon , south korea ) .
the signal was sampled at a rate of 256  hz and was digitally 
 filtered using a 150-hz band - pass filter .
after data acquisition and storage , all 
 statistics were computed to extract asymmetry values for the alpha frequency band in the 
 frontal area of the cerebral cortex19,20,21 . 

the asymmetry index was calculated by subtracting the log - transformed absolute alpha power 
 of the left hemisphere from the analogous log - transformed right hemisphere alpha power ( log 
 right  log left ) . as alpha power
is inversely associated with cortical activation , a 
 negative asymmetry score , which denotes greater alpha activity on the left and less alpha 
 power on the right , would suggest greater right - sided activation . on the other hand ,
the asymmetry index was compared prior to , and after , 
 mld application using a paired t - test , and the collected data were analyzed using a 
 statistical package program ( spss v. 19.0 ) .
mld generally caused an activation shift from the right hemisphere to the left hemisphere 
 in all frontal electrode pairs analyzed in this study .
statistical analysis comparing pre- 
 and post - mld asymmetry values in channels f7f8 showed a statistically significant increase 
 in hemispheric asymmetry : fp1fp2 , p = 0.082 ; f3f4 , p = 0.065 ; and f7f8 , p = 0.032 . 

alpha asymmetry scores for each regionareabefore- mldafter- mldfp1fp20.130.060.030.18f3f40.150.050.020.16f7f80.120.040.090.25 * all variables are means  sd , mld : manual lymph drainage , * p<0.05 .
in this preliminary study , frontal lobe eeg activity patterns in response to mld of the 
 neck were examined to better understand alpha wave processing in subjects with psychological 
 stress .
many studies have shown that eeg asymmetry can be attenuated by massage , relaxation 
 techniques , and musical therapies22,23,24 . 

however , to date , there are no studies investigating the effects of mld on frontal 
 asymmetry .
mld application acts as a very light stimulator against psychological stress ; we predicted 
 that mld would be associated with frontal eeg asymmetry and state , and specifically result 
 in greater left frontal hemisphere activation in the alpha frequency band . in this study , 
 the alpha band ( typically in the range of 813  hz ) was chosen as an electrophysiological 
 marker because , as previously discussed , it is relatively stable21 , 25 and inversely 
 related to activation26,27,28 .
the measurement 
 of alpha asymmetry has been shown to be effective and reliable in discriminating positive 
 and negative emotions23 , 29 . since
previous investigations have demonstrated a 
 relationship between brain electrophysiology in the frontal area and measures of affective 
 states19 , 20 , 30 , 31 , we have also focused our analysis on the three anterior electrode 
 pairs , fp1fp2 , f3f4 , and f7f8 .
recent studies have suggested that greater left - sided anterior activation , indexed by 
 decreased alpha activity in the left hemisphere , is associated with a higher degree of 
 positive affectivity , a feeling of well - being , and a reduction in anxiety28 , 32 .
our results indicate that mld is associated with a significant 
 increase in left - sided anterior activation , thus supporting our hypothesis that mld can 
 attenuate frontal eeg asymmetry .
these results are also in line with findings from previous 
 studies that have demonstrated the therapeutic effects of massage4 , 5 , 20 .
although this study showed demonstrable effects of mld , there are several limitations and 
 suggestions for future research .
firstly , this study only examined the acute 
 electrophysiological changes produced after mld in subjects with psychological stress . in 
 addition to replicating the present findings with a bigger sample size ,
further studies are 
 needed to investigate the effects of mld on other clinical populations across different 
 conditions and diseases under a more controlled experimental design . in conclusion
, our preliminary study showed that mld can significantly increase left - sided 
 anterior activation .
these results provide evidence to support the hypothesis that mld gives 
 rise to positive affectivity .
   [ purpose ] the purpose of this preliminary study was to investigate the effect of manual 
 lymph drainage ( mld ) of the neck on frontal electroencephalogram ( eeg ) asymmetry in 
 subjects with psychological stress . 
 [ subjects ] thirteen subjects with psychological stress 
 participated in the study . [ methods ] 
 subjects received mld of the neck for 15  min . 
 
 [ results ] analysis of the frontal asymmetry index showed that the energy shift in the 
 alpha frequency band from the left hemisphere to the right hemisphere after mld resulted 
 in greater left - side activation ( positive asymmetry values ) , which could be related to the 
 positive emotional state observed particularly in the f7f8 area . 
 [ conclusion ] these 
 preliminary findings suggest that frontal eeg asymmetry was significantly attenuated after 
 mld . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION