owing to the development of transportation and increased leisure time , the frequency of 
 damage in nervous tissue , especially in peripheral nerves , is on the rise1 . the clinical problems of peripheral nerve 
 damage are motor paralysis of muscle , sensory paralysis , and functional loss , and such 
 neurological injuries are mostly caused by strong crushing and cutting due to an external 
 force2 . additionally , pain from sciatic 
 nerve damage can be caused by herniated nucleus pulposus ( hnp ) , spinal stenosis , and 
 piriformis muscle syndrome and may lead to hip pain and functional loss and paresthesia of 
 lower extremities3 . peripheral nerve 
 damage eventually generates partial or total loss of the motor , sensory , and autonomic 
 nervous systems including body segments4 . compensation for a functional disorder caused by neurological injury consists of 
 reinnervation of neural paralysis by regeneration of damaged axon terminals , reinnervation 
 from neighboring undamaged axon terminals to dendritic branches , and reformation of neural 
 system circuits relating to lost functions1 . however , this mechanism does not come with satisfying functional 
 restoration and it is hard to expect recovery in the case of severe neurological injury4 . microsurgical techniques such as neurorrhaphy and nerve grafting are used to repair severe 
 neurological injury . lundborg5 proved that 
 acute electrical stimulation after sciatic nerve damage accelerated muscle reinnervation 
 improvement and axonal regeneration . in addition , long - term moderate - intensity treadmill 
 exercise with acute electrical stimulation in the beginning of nerve regeneration was found 
 to be more effective6 . previous studies 
 reported that active and passive exercise using bicycle training was effective for sciatic 
 nerve damage7 , treadmill exercise 
 accelerated functional recovery and decreased neuropathic pain8 , and swimming exercise after a sciatic nerve crush injury 
 accelerated muscle recovery9 . a number of 
 recovery methods for peripheral nerve damage have been analyzed as mentioned above , but 
 these analyses only focused on the exercise method or intensity , and there are few studies 
 about weight - bearing and non - weight - bearing exercise . therefore , the purpose of this study 
 was to access the effect of weight - bearing exercise ( treadmill exercise ) and 
 non - weight - bearing exercise ( swimming exercise ) on gait in the recovery process after a 
 sciatic nerve crush injury . this study was conducted with 6 male white sprague - dawley rats at 8 weeks of age . these 
 rats weighed 250300 g and were bred three rats per cage in a breeding room at a temperature 
 of 232  c and humidity of 505% during the test . solid feed ( cargill agri purina inc . , seongnam , republic of korea ) and water were 
 provided without limitation to the rats . this study was conducted in compliance with the 
 guide for the care and use of laboratory animals and with the permission of our 
 institutional animal care and use committee . zoletil ( virbac laboratories ) and rompun ( bayer korea ) mixed at a 1:1 ratio were 
 intraperitoneally injected at 2  ml / kg body weight into the rats for general anesthesia . the right femoral and knee 
 joint region of the animals were shaved while they were fixed on the operating table to 
 measure sciatic nerve crush injury and gait . then , a 2  cm incision was made in the right 
 posterior femoral region , the surrounding muscles were separated , and the proximal region 
 ( 7  cm from the ankle joint , ahead of the tibial and non - tibial nerve branching off from the 
 sciatic nerve ) was compressed for 30  min using hemostatic forceps ( crile ) . the forceps were 
 covered with soft plastic during application of pressure . a suture using suture thread for animal testing was 
 applied , and the skin was disinfected . the rats were allowed to acclimate to the environment 
 in standard plastic cages ( 290  430  180  mm ) , three rats per cage , until the 
 intervention . the rats were randomly divided into a swimming group ( n=3 ) with non - weight - bearing exercise 
 after induction of the sciatic nerve crush injury and a treadmill group ( n=3 ) with 
 weight - bearing exercise after induction of the sciatic nerve crush injury . ankle and knee angles of all white rats were evaluated using the dartfish program 
 ( prosuite , dfkorea , seoul , republic of korea ) at 3 , 7 , and 13 days after the intervention 
 for motor behavioral motion analysis according to recovery from the sciatic nerve damage . the knee 
 lateral epicondyle , lateral malleolus , and metatarsophalangeal joint of the fifth toe were 
 marked by black dots before recording . the rats walked on a transparent pathway ( 100  cm 
 long , 8  cm wide , and 10  cm high ) during recording . they did this three times to get used to 
 the pathway and then repeated it three times for the evaluation . they were recorded with a 
 digital video camera placed 1  m away from the pathway in the sagittal plane . the independent 
 t - test was used for comparison of the results of the motor behavioral test between the two 
 groups . one - way anova was used to analyze significant differences among groups and measuring 
 periods . ibm spss 
 statistics for windows , version 20.0 , was used for statistical processing , and the 
 statistical significance level was set to  = 0.05 . there were significant differences in tok ( knee angle toe off ) and ick ( knee angle at 
 initial contact ) in the treadmill group ( p<0.05 ) and in tok , ica ( ankle angle at initial 
 contact ) , and ick in the swimming group ( p<0.05 ) . in comparison between groups , there 
 were significant differences in toa ( ankle angle at toe off ) and ica at the 7th day 
 ( p<0.05 ) ( table 1table 1.comparison of gait for each groupvariable3 days7 days13 daysto - atmg40.035.4743.853.9446.107.87smg44.3710.4051.477.9145.106.77to - ktmg71.8010.7071.028.2153.545.62smg75.2112.3078.5312.9151.7012.45ic - atmg60.069.6964.476.2270.328.21smg55.6675.0375.038.0765.5715.46ic - ktmg84.7010.9591.115.6177.182.09smg87.5014.6193.004.0468.7512.99*p<0.05 . to - a : ankle angle at toe off ; to - k : knee angle toe off ; ic - a : ankle angle 
 at initial contact ; ic - k : knee angle at initial contact ; tmg : treadmill exercise 
 group ; smg : swimming exercise group . significant difference between 
 periods . significant difference between tmg and smg ) . off ; to - k : knee angle toe off ; ic - a : ankle angle 
 at initial contact ; ic - k : knee angle at initial contact ; tmg : treadmill exercise 
 group ; smg : swimming exercise group . significant difference between 
 periods . peripheral nerves damage causes pain and deficits in sensory and motor nerves , and 
 regeneration ability depends on damage level10 , 11 . there is no functional recovery method for severe nerve injury , and surgical repair is 
 generally used12 . in addition , owing to 
 natural reinnervation and damage to neural factors necessary for recovery of damaged 
 function , active neural redistribution may not be expected13 . there are many studies about intervention methods , particularly 
 those using external stimulation . in this study , a gait analysis was used as an effectiveness evaluation for therapeutic 
 intervention , and the effect of weight - bearing exercise using a treadmill and 
 non - weight - bearing exercise ( swimming ) on gait in the recovery process after a sciatic nerve 
 crush injury was assessed . after peripheral nerve damage , axons in the damaged region are disconnected from nerve cell 
 bodies and degenerated , and neural responses and chromatolysis form in the damaged nerves . wallerian degeneration generates a microenvironment in the distal region and causes neural 
 responses for regeneration and elongation and regrowth of surviving axons . in the axonal regeneration process in the damaged nerve , schwann cells proliferate in the 
 damaged area and move to the distal region , followed by axonal contact and regeneration . schwann cells proliferate until complete regeneration , and a myelin sheath is ultimately 
 formed14 . neurotrophic factors are involved in the growth and differentiation of nerve cells , and all 
 neurotrophins have similar biochemical characteristics . the expression level of 
 neurotrophins and their acceptors can change according to neural activity . neurotrophins are 
 an important factor for sensorimotor function control15 , 16 . after rats with sciatic nerve damage conducted wheel running exercise , neurotrophins and 
 nerve regeneration gutmann and jakoubek20 reported that swimming exercise for recovery from sciatic nerve 
 damage increased axonal growth and that treadmill running exercise increased reinnervation , 
 axonal elongation , and sprouting . these results are consistent with the results of this 
 study , that is , that treadmill and swimming exercise were effective for nerve recovery . there was a decrease in gait ability at the beginning of testing ( first 7 days ) . this was a 
 period of inflammatory response and recovery for other tissues and with wallerian 
 degeneration after 4 days , nerve function was considered to decrease21 . the results of the present study showed no substantial 
 difference between treadmill and swimming exercise . therefore , there was no difference 
 between the effects of weight - bearing and non - weight - bearing exercise on sciatic nerve 
 damage , and both exercises accelerated the recovery process in this study . a limitation of 
 this research is that only gait ability was measured , so neurotrophins expression should be 
 evaluated in further studies .
[ purpose ] the purpose of this study was to access the effect of weight bearing exercise 
 ( treadmill exercise ) and non - weight - bearing exercise ( swimming exercise ) on gait in the 
 recovery process after a sciatic nerve crush injury . [ subjects and methods ] rats were 
 randomly divided into a swimming group ( n=3 ) with non - weight - bearing exercise after a 
 sciatic nerve crush and a treadmill group ( n=3 ) with weight bearing exercise after a 
 sciatic nerve crush . 
 dartfish is a program that can analyze and interpret motion through 
 video images . 
 the knee lateral epicondyle , lateral malleolus , and metatarsophalangeal 
 joint of the fifth toe were marked by black dots before recording . 
 [ results ] there were 
 significant differences in tok ( knee angle toe off ) and ick ( knee angle at initial 
 contact ) in the swimming group and in tok , ica ( ankle angle at initial contact ) , and ick 
 in the treadmill group . in comparison between groups , there were significant differences 
 in toa ( ankle angle in toe off ) and ica at the 7th day . 
 [ conclusion ] there was no 
 difference between weight bearing and non - weight - bearing exercise in sciatic nerve damage , 
 and both exercises accelerated the recovery process in this study .