massotherapy , defined as a manipulation of the soft tissues , is often provided to specific 
 areas or whole body parts aiming at the following effects : enhanced blood flow , relief of 
 muscle tension , improvement of autonomic nerve functions , prevention of bad conditions or 
 injuries , and easing of pains1,2,3 . in recent years , 
 massages have been admitted in international treatment guidelines4 , 5 as one of the 
 recommended therapies requiring further scientific verification . massages are provided in the following cases : subcutaneous emphysema caused by fracturing 
 the breastbone or ribs , external injuries , chest bruises , and crashes6 ; treatment at childbirth that shortens the delivery 
 time7 ; healing of cobb angle of 
 idiopathic scoliosis8 ; relief of patients 
 suffering from musculoskeletal disorders including back pain9 . massages are reported to be effective to alleviate pain and to 
 enhance bodily functions . however , while these reports refer to the effects of massages , 
 there are some cases which do not actively research the mechanism for how the massage is 
 effective . therefore , there are those who insist that massotherapy lacks scientific evidence 
 and needs to be verified scientifically10,11,12 . in clinical practice , we obtained certain effects such as the relief of pain or improvement 
 of the range of joint motion by providing friction to patients with popliteal edemas due to 
 osteoarthritis of the knees or disorder of venous flow . hammer s report referred 
 to histamine or bradykinin as the elements involved in the effects of friction provided to 
 chronic bursitis of the hip and shoulder joints14 . it was assumed that the effect to alleviate pain or to enhance the 
 range of motion after providing friction would facilitate healing of edemas and relief of 
 pain while enhancing the blood flow of the popliteal vein caused by the vascular dilatation 
 or the vasodilator action by use of histamine or bradykinin . physiologically , the lower legs venous sinuses play a major role in venous return , and 
 venous sinuses in the soleus and gastrocnemius play the main role . anatomically , these 
 venous sinuses flow into the popliteal vein directly and indirectly through the posterior 
 tibial and peroneal veins . accordingly , the condition of lower legs venous return is reflected in 
 the rate of blood flow passing through the popliteal vein . it was clarified that friction 
 massage of the region below the popliteal fossa causes dynamic changes in muscle 
 oxygenation15 , but it was unclear what 
 influence this effect has on venous return . based on this assumption , an aim was set at researching the influences of friction on the 
 popliteal region as a manipulation of the body surface , and at considering the mechanism of 
 friction s effects from the viewpoint of venous flow . during this study , friction massage was performed on the area surrounding the popliteal 
 vein in healthy volunteers . friction massage was performed on the intermediate point between 
 the medial and lateral heads of the gastrocnemius muscle . friction massage was performed by 
 the thumbs , moving them in small circles ( 23 cm ) at a frequency of 3  hz . changes in blood flow velocity of the popliteal vein was 
 monitored before and after intervention ( a comparative study : after versus before ) . fifteen male students who satisfied the selection criteria were gathered from ibaraki 
 prefectural university of health sciences as subjects ( means  sd : age=21.4  1.7  years ) . the subjects signed a letter of consent after the purpose of the study , method , benefits and 
 risks , and rights of participants were explained . exclusion criteria were as follows : diagnosis or evidence of any cardiovascular , 
 metabolic , orthopedic , neurological or endocrine disease that are known to affect 
 endothelial function ; use of any medication that can interfere with cardiovascular function ; 
 and a risk of adverse response to exercise . the study protocol was approved in advance by 
 the authors institutional review board and adhered to the declaration of helsinki . written 
 informed consent was obtained from all of the individual participants included in the 
 study . the subjects underwent a single testing session in which all of the experimental procedures 
 were conducted . before reporting to the laboratory , subjects were asked to fast and refrain 
 from caffeine , tobacco , alcohol , and strenuous physical activity for at least 12  h before 
 the experiment . the measurement profiles of the blood flow velocity were obtained from pictures of the 
 right popliteal vein by reference to the international guideline17 . based on all the pictures , the sizes in vein diameter and 
 blood flow were analyzed utilizing a logiq book xp ( ge healthcare products , milwaukee , wi , 
 usa ) system with an 8 mhz linear transducer . the pictures of popliteal veins were identified 
 in the b mode on the location two centimeters from the central region of the popliteal 
 fossa . gain settings were adjusted in order to get appropriate views of the front and the 
 rear of the intimal interfaces of veins , thus identifying the vein in the color 
 doppler - mode . a measurement setting was then conducted for the vascular caliber ( sample 
 volume ) of the popliteal veins . doppler velocity profiles were collected simultaneously 
 using a pulsed signal at a corrected insonation angle of 60 to the vessel , with the 
 velocity cursor positioned mid - artery to sample the volume . all pictures were captured by a 
 usb video board at a frequency of 30  hz , and then saved in the external hard drive in order 
 to be analyzed offline afterwards . measurement of the popliteal vein was conducted using doppler ultrasonography with the 
 subjects in a prone position . initially , the subjects were placed in a prone position for 20 
 minutes at a constant temperature of 2426  c ( relative humidity at 4060% ) for acclimation 
 according to the experimental protocol ( fig . after that , the blood flow velocity of the popliteal vein was measured for the 
 first time . next , friction was provided for two minutes and then the blood flow velocity was 
 measured for the second time . the transition was then analyzed with the first measured value 
 set as the base line . measurement parameters , such as average blood flow velocity ( v mean ) , 
 pulsatility index ( pi ) , and resistance index ( ri ) , were utilized18 , 19 . experimental protocol statistical analyses focused on differences between pre - friction and post - friction blood 
 flow velocity states of the popliteal veins measured using doppler sonography . changes in 
 parameters were compared using within - subject paired t - tests . participants characteristics are shown in table 
 1table 1.characteristics of study participantsparameters(n=15)age ( years)21.4  1.7height ( cm)173.6  3.8weight ( kg)59.3  3.2bmi ( kg / m)19.7  0.9values are expressed as means  sd.bmi : body mass index . in addition , parameter values before and after friction are shown in table 2table 2.blood flow velocity changes before and after friction massageprepostblood flow velocity ( cm / s)13.8  2.8 23.3  6.9*values are expressed as means  sd . significantly different between pre- and post - friction measurements , * p<0.01 . when a t - test was conducted , there were significantly large differences 
 between pre- and post - friction measurements ( t=7.162 , df=14 , p<0.01 ) . based on this 
 result and the average values , it is possible to understand that the blood flow of the 
 popliteal vein had a higher velocity after friction compared to before friction . in this study , regarding the venous flow of the lower legs , the effects of friction on 
 popliteal regions was evaluated , using the blood flow velocity of the popliteal vein as an 
 index . the blood flow velocity of the popliteal vein increased when friction was provided to 
 the popliteal region . based on this result , it was shown that friction is effective to 
 improve the venous flow of the lower legs . due to the fact that the lower legs , including 
 the gastrocnemius and soleus muscles , have anatomical characteristics such as specific forms 
 of vascular channels20 , lower legs 
 compartment syndrome , deep venous thrombosis , edema , and venous congestion are prone to 
 occur . the result of this study showed that friction had an effect to heal these clinical 
 conditions and disorders . moreover , adding to circulatory disorders caused by the anatomical characteristics of the 
 lower legs vascular channels , there are also disorders caused by autonomic nervous system 
 malfunctions21 and disorders of the 
 metabolism22 . diabetes is one disorder 
 of the metabolism which invokes muscle pain or muscle fatigue due to disordered blood 
 circulation . therefore , it is considered that enhancing the venous flow of the lower legs 
 would alleviate pain and relieve muscle fatigue . furthermore , it is expected that friction 
 can be used as physical therapy to facilitate healing of injured parts during the period 
 where muscle contraction is not available due to muscle injury , patients being in the 
 postoperative period , and when body parts are bound in a cast . it is also pointed out that 
 friction has other effects such as an enhancement of the circulation when being provided 
 strongly enough to cause neurogenic inflammation . that is , when the massage is provided to 
 the skin , the nociceptor is stimulated , inducing the discharge of neuropeptide such as 
 substance p from the cell body . this stimulates not only the central nerves but also 
 descends to the peripheral nerves , inducing the peptide from the sensory nerve terminal . it 
 has been explained that as a result of the above process , the mast cells and the internal 
 smooth muscles widen the blood vessels23 . the authors believe it to be necessary to start substantiating the study of these 
 effects . since dysfunction of the lower legs venous system , which plays the main role in venous 
 return , is involved in the development of circulatory disorder in many cases , the indication 
 of friction massage for circulatory disorders , such as lower legs compartment syndrome , 
 edema , and diabetic muscle pain , was suggested . however , the results were obtained from 
 young subjects and the autonomic and blood flow - related nervous systems were not 
 investigated , and these are limitations of this study .
[ purpose ] friction massage ( friction ) of the popliteal fossa is provided for the purpose 
 of relieving pain related to circulatory disorders by improving venous flow in the lower 
 legs . 
 the purpose of this study is to verify the effects of enhancing the venous flow 
 based on measuring the blood flow velocity of the popliteal vein before and after 
 providing friction to the patients . 
 [ subjects and methods ] fifteen healthy male university 
 students participated in the study . the doppler ultrasonography ( du ) 
 was used to measure 
 the blood flow velocity of the popliteal vein , in order to verify the effects of enhancing 
 the venous flow by comparing the measured values before and after a friction massage . 
 [ results ] the result of comparing the blood flow velocity before and after providing 
 friction showed that there was a significant increase after friction . 
 [ conclusion ] this 
 study proved that friction to the popliteal fossa is effectively enhances venous flow by 
 increasing the blood flow velocity in the popliteal vein .