it is 
 characterized by local degenerative changes in joint cartilage , condrocyte hypertrophy , 
 excessive osteophyte formation in the bones connected with the joint , and joint deformities 
 of the weight - bearing joints , and it causes repetitive pain , joint stiffness , and gradual 
 motor disturbance1 .
the incidence of 
 osteoarthritis in elderly people aged 65 or above is over 80% , and it is gradually 
 increasing with time . while the precise causes of osteoarthritis are not known
, chronic 
 osteoarthritis results from abrasion of the joints due to aging , and later , it occurs due to 
 various biological and mechanical factors that cause cartilage degeneration .
the goal of 
 treatment for osteoarthritis is to reduce pain , regenerate cartilage , and recover function 
 by suppressing the factors that cause cartilage degeneration as much as possible2 .
osteoarthritis patients experience pain , 
 stiffness , and edema due to inflammation in the joint , as degenerative changes progress 
 around the joint and the lower part of joint cartilage .
in addition , loss of joint function 
 occurs due to joint deformation , the exudation of joint fluid , weakening of the muscles 
 around the joint , and reduced muscle strength resulting from the destruction of joint 
 cartilage3 .
these symptoms exhibit as 
 rubefaction , fever , and edema as inflammatory responses , or pain and functional losses , and 
 they are generally accompanied by physical limitations that differ from those due to 
 external injuries such as contusions or penetrative wounds4 . pain and limitations in the joint range of motion ( rom ) occur due 
 to degeneration caused by mechanical stimulation and friction that are continuously 
 experienced by joint cartilage , and changes caused by other articular tissues5 .
today , the most frequently used 
 exercise for both humans and animals is walking , and walking on a treadmill or in water is 
 performed most commonly6 .
the purpose of 
 treatment for osteoarthritis is to reduce pain and minimize functional losses by maintaining 
 or improving joint function .
however , while the current selective therapies for 
 osteoarthritis include exercises and medication , such as the administration of systemic 
 analgesics , detailed exercise methods have not been explained , and medication involves the 
 risk of serious sideeffects of drugs .
accordingly , the purpose of this study was to identify 
 whether walking on a treadmill at an adjusted speed is suitable for humans by examining the 
 effects of exercise on the joint function of white rats with induced knee 
 osteoarthritis .
the study subjects were twenty sprague - dawley white rats , aged eight weeks , weighing 250 to 
 300 g. during the experiment , the dietary intake of the test animals was not limited , and 
 their breeding room s environment was maintained under the optimal conditions of 25  3  c , 
 and 60  5% humidity , and a light / dark cycle of 12 hours ( light cycle : 08:0020:00 , dark 
 cycle : 20:0008:00 ) .
osteoarthritis was induced in the test animals after environmental 
 adaptation for two weeks in the breeding room .
then , they were randomly divided into a 
 moderate - speed exercise group ( n=10 ) , and a high - speed exercise group ( n=10 ) . this 
 experiment complied with the experimental ethics .
osteoarthritis was induced as follows : the test animals were anesthetized by 
 intraperitoneal injection ( 2  ml / kg ) of a general anesthetic produced by mixing zoletil and 
 rompun ( bayer korea , korea ) at a ratio of 1:1 , one week before performing treadmill 
 exercise .
then , they were injected in the joint cavity of their right knee with monosodium 
 iodoacetate ( mia ; sigma , st louis , mo , usa ) diluted with a 50  l saline solution using a 26 
 gauge syringe .
after the injection , extension and flexion were repeated for about five 
 minutes to spread mia into the joint cavity evenly . if a rat exhibited symptoms such as 
 fever , edema or oppressive pain in the knee three weeks after the injection of mia , the rat 
 was diagnosed as having osteoarthritis7 . 

this study set the treadmill speed following the protocol of rodrigues , and the test animals 
 performed walking exercises on a treadmill for small animals ( jd - a-09 type , jeungdo bio 
 & plant co. , ltd .
the two exercise groups were first trained to adapt to their 
 main treadmill exercise by walking on the treadmill at a gradient of 0% and a speed of 8 
 m / min for 15 minutes for two days , and they performed the main exercise after a one - day 
 break8 .
the moderate - speed exercise 
 group performed their exercise at a gradient of 0% and a speed of 15 m / min , and the 
 high - speed exercise group performed their exercise at a gradient of 0% and a speed of 26 
 m / min .
the exercise was performed at 7:00 pm in the evening when the test animals typically 
 showed a lot of activity .
when an animal stopped the given exercise , they were encouraged to 
 continue to exercise by applying an electrical stimulus of 10 volts via a device installed 
 in the lower part of the treadmill s belt ( table 1table 1.protocol of treadmill exercisegroupnduration(weeks)frequency(days
/ week)speed(m / min)exercise time(min)mseg10251630hseg10252530mseg : moderate speed exercise group ; hseg : high speed exercise group ) .
the aim of this study was to examine changes in knee angle and stance time . 

kinematic motions at the different walking speeds were evaluated using dartfish sofrware 
 ( prosuite , dfkorea , korea ) at one day and 14 days after the animals had been treated .
mseg : moderate speed exercise group ; hseg : high speed exercise group after disinfecting each rat s hind leg with alcohol and shaving the relevant region , the 
 lateral epicondyle of the knee , lateral malleolus of the ankle , and metatarsophalangeal 
 joint of the fifth toe were marked with black dots , and the rats were filmed in the sagittal 
 plane ; the average of three repeated values was adopted for use9 .
this study confirmed the significance of group differences 
 using the independent sample t - test .
spss win . 18.0 for windows was used to compare 
 kinematic changes between the treadmill speeds .
statistically significant changes were elicited by the moderate - speed and high - speed 
 exercises . for the moderate - speed exercise ,
the knee angle changed from 104.5  0.6 to 92.5 
  2.4 , and the stance time changed from 327.1  64.6  ms to 288.6  49.1  ms . for the 
 high - speed exercise ,
the knee angle changed from 104.5  0.5 to 96.7  1.0 and the stance 
 time changed from 295.1  33.7  ms to 377.4  63.0  ms ( table 2table 2.comparison of changes in the moderate speed and high speed exercise 
 groupsmseghsegprepostpreposticak ( )104.5  0.692.5  2.4104.5  0.596.7  1.0*icspt ( ms)327.1
 64.6288.6  49.1295.1  33.7377.4  63.0*icak : initial contact angle knee ; icspt : initial contact stance phase time ; mseg : 
 moderate speed exercise group ; hseg : high speed exercise group ; * p<0.05 ) .
icak : initial contact angle knee ; icspt : initial contact stance phase time ; mseg : 
 moderate speed exercise group ; hseg : high speed exercise group ; * p<0.05
this study examined the effects of different treadmill walking speeds on the knee angle and 
 stance time in the initial contact stage of white rats with induced knee osteoarthritis .
the 
 aim was to suggest a more effective exercise by determining the appropriate speed at which 
 osteoarthritis patients should perform walking exercises .
this study filmed the rats with a 
 video camera and analyzed their moving images with the dartfish software to learn about the 
 changes in the functional walking of white rats with knee osteoarthritis elicited by 
 different speeds of change treadmill exercise .
individuals with knee osteoarthritis 
 generally exhibit a reduced ability of lower - extremity joints in functional walking , and 
 when osteoarthritis occurs , reduction in the knee angle and range of motion of the knee , and 
 atrophy in the muscles around the affected region may occur10 .
another complaint of osteoarthritis patients is that they 
 experience limitations in daily activities such as walking , walking up stairs , and 
 housework . in general , these patients additionally experience obesity - related disorders such 
 as heart diseases , high blood pressure , and diabetes , and depression or sleep disturbance 
 which all reduce the subjects quality of life and satisfaction with life11 .
these problems can be improved through 
 proper exercise , and osteoarthritis patients can improve their gait ability and experience 
 positive effects on their daily lives and occupational environments by performing specific 
 exercises12 .
walking is a type of 
 locomotion specific to humans , which is essential in daily life . in recent years , it has 
 been widely performed as an exercise for health , and is the most natural motion for 
 humans13 .
a study reported that 
 lower - extremity muscle strengthening exercises and treadmill walking exercises had positive 
 effects on balance ability and skeletal musclestrength14 .
in addition , walking exercises have positive effects on 
 cardiorespiratory functional capacity15 , 
 and when stroke patients walking outside and walking on the treadmill were compared at low 
 and high speeds , statistically significant changes were observed in endurance , walking 
 speed , and balance ability16 .
another 
 study instructed hemiplegic patients to walk at a speed of 1  km / h for 30 seconds , have a 
 break , and then walk again at a speed of 2  km / h for 30 seconds after adapting to this main 
 walking exercise by initially walking at comfortable speeds .
these changes in walking speed 
 influenced foot rotation , weightbearing responses , and joint movements in the mid - stance and 
 swing phases17 .
a study was conducted to 
 analyze dynamic changes in the knee and gait characteristics of patients with knee 
 osteoarthritis walking at a high speed .
this study also noted that an increase in walking 
 speed is correlated with an increase in the range of the joint movement18 .
moreover , another study provided a normal individual and 
 a patient with knee osteoarthritis with different variables for walking conditions .
when the 
 subjects selectively adjusted their walking speed themselves or performed fast walking , they 
 exhibited functional changes in the joints19 .
the above research results suggest that changes in walking speed 
 during walking exercise may be associated with the effects of the exercise .
while the cited 
 studies mostly examined neurological patients performing walking exercises , future studies 
 should examine musculoskeletal patients . in conclusion ,
in particular , they demonstrate that changes 
 in knee rom and stance time were generated as the walking speed changed .
the knee joint s 
 angle during the early - stance phase showed changes in both the moderate - speed and high - speed 
 exercise groups , and the high - speed walking group exhibited statistically significant 
 changes in knee angle .
this shows that the degree of joint stiffness , a characteristic of 
 progressive knee osteoarthritis , gradually increased .
moreover , changes in early stance time 
 were also statistically significant in the high - speed walking group .
this suggests that pain 
 was at a moderate level despite weight - bearing during the stance phase .
 [ purpose ] the purpose of this study was to identify whether walking on a treadmill at an 
 adjusted speed is suitable for humans by examining the effects of exercise on the joint 
 functions of white rats with induced knee osteoarthritis . 
 [ subjects and methods ] the 
 subjects were 20 sprague - dawley white rats , aged eight weeks , weighing 250 to 300  g. the 
 moderate - speed exercise group performed their exercise at a gradient of 0% and a speed of 
 15 m / min , and the high - speed exercise group performed their exercise at a gradient of 0% 
 and a speed of 26 m / min . 
 [ results ] statistically significant changes were elicited by the 
 moderate - speed and high - speed exercises . 
 [ conclusion ] in conclusion , the results of the 
 present study present the importance of walking exercise . in particular , they demonstrate 
 that changes in knee rom and stance time are elicited by changes in walking speed . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION