the anterior cruciate ligament ( acl ) is the most frequently injured knee ligament , and 
 accounts for about 50% of all ligament injuries1 .
acl injury is a common cause of knee instability and alters the 
 kinematics of the knee2 .
most are caused by non - contact injury 
 mechanisms , such as landing from a jump , or rapid deceleration3 .
an acl injury typically occurs during the landing portion of a jump 
 in ordinary sports activities and has a greater incidence among women than among men4 .
patients with acl injury often have symptoms of knee 
 instability , which may lead to functional change in and damage to other joint structures , 
 and interfere with activities of daily living5 .
patients with acl injuries have difficulty recovering normal 
 walking ability and full function of the lower limbs6 .
knee instability following acl injury results in various negative factors , which can be 
 circumvented using acl reconstruction .
reconstructive techniques have been refined to 
 achieve better stabilization of the knee and other joints in order to improve functional 
 recovery7 .
it has been suggested that 
 the lack of full recovery of knee function after acl reconstruction is due to sensory and 
 motor behavior deficits .
muscle strength , endurance , flexibility and balance training are 
 used as therapeutic exercises in rehabilitation settings .
proprioceptive afferent neural 
 input is also important in functional control during sports activities8 . in the clinic ,
patients are always asked to walk normally , 
 but few exercise methods provide normal proprioceptive input during walking training . in recent years ,
robot - assisted therapy ( rat ) rehabilitation , which simulates normal 
 walking , has also been used to help patients with spinal cord injury or stroke9 .
the major difference between robot - assisted weight - supported treadmill training and 
 existing supported ambulation training is the addition of a mechanical assistant in the rat , 
 so that alternative steps with both feet can be achieved by patients10 .
moreover , simulation of a normal walking pattern 
 facilitates input from the peripheral nerves . in this manner ,
the remaining central nervous 
 system can be stimulated so that regeneration of the nerves involved in traumatic spinal 
 cord injury can be completed .
recent studies have shown that this method is associated with 
 significant improvements in reaction time and bowel function11 , 12 .
the aim of this study was to examine the long - term interventions effects of rat 
 rehabilitation on functional activity levels after acl reconstruction .
this study recruited 8 patients who underwent arthroscopic acl reconstruction in boai 
 hospitals in beijing , china , between september and december 2015 .
patients performed 
 rehabilitation exercises for at least 2 months at the department of physical therapy .
the 
 subjects were limited to patients who had undergone acl reconstruction with autografts , 
 performed by the same surgeon , and showed no differences in anatomical stability based on 
 radiographic and magnetic resonance imaging .
the characteristics of the 8 subjects ( 6 males and 2 females ) are shown in table 1table 1.subject characteristicsmean  sd ( n=8)age ( yrs)35.2  3.2height ( cm)173.4  8.6weight ( kg)79.5  16.8 . the subjects participated in rat for one month .
the purpose and content of 
 this research were explained to the subjects , who gave their informed consent to 
 participation in this study .
the study was approved by the research ethics committee of 
 china rehabilitation research center ( irb no .
was carried out as traditional 
 physiotherapy , which included the muscle strength training , joint mobilization , balance 
 training , and endurance training .
the walking training used a rehabilitation training robot 
 ( mbz - cpm1 , manbuzhe [ tian jin ] rehabilitation equipment co. , ltd . , china ) . in the treadmill 
 and rat training ,
the initial training speed was 1.5  km / h , which was progressively increased 
 to 1.8  km / h as quickly as possible while maintaining gait quality13 .
the body weight system was initiated at 35% , and 70% 
 guidance force was provided for the participants14 .
the walking training lasted for 20  min a day , and was performed 5 
 times a week .
the extension strength of the knee joint , and walking and balance abilities 
 were measured before and after the one - month intervention .
walking ability was evaluated using the 10-meter walk test ( 10mwt ) and the timed up - and - go 
 ( tug ) test .
balance ability was assessed using the functional reach test ( frt ) . for the 
 assessment of knee extension strength , surface electromyography
( semg ) and the maximal 
 extensor strength of the knee joint were measured with the subjects seated and the knee 
 flexed at 45. in the semg evaluation of the vastus lateralis ( vl ) and vastus medialis ( vm ) muscles , 
 maximum isometric contraction in the start position was maintained for 5  s , during which the 
 maximum and average semg values of the muscle were measured by an semg system ( telemyo 
 2400 t ; noraxon , scottsdale , az , usa ) .
the maximum and average extensor strengths of 
 isokinetic movement of the knee joint were measured using an isokinetic dynamometer ( prima 
 plus , easytech , italy ) .
the 
 wilcoxon test was used to compare the 10 mwt , tug , frt , the maximum and average semg values 
 of vl and vm , and the maximum and average extensor strengths of the knee joint isokinetic 
 movement before and after the one - month intervention .
all the subjects in this study received rat training 20 times over one month . the results 
 of the 8 subjects
are shown in table 
 2table 2.the long - term interventions effects of rat10mwt ( s)tug test ( s)frt ( cm)maximum semg value of lateralis(v)average semg value of lateralis(v)maximum semg value of medialis ( v)average semg value of medialis ( v)maximum extensor strength ( nm)average extensor strength ( nm)before one month rat intervention8.8  1.1 * 10.0  0.819.3  5.1**1,872.2  966.0280.3  131.11,405  676.5189.5  60.3 * 41.0  22.3 * 37.0  21.7**after one month rat intervention7.3  0.3 * 9.5 
1.626.5  4.8**1,915.7  827.4315.0  113.51,590  261.7230.3  67.2 * 52.3  24.1 * 47.7  22.5***p<0.05 ; * * p<0.01 .
10mwt : 10-meter walk test ; tug : timed up - and - go ; frt : functional reach test ; rat : 
 robot - assisted therapy .
10mwt : 10-meter walk test ; tug : timed up - and - go ; frt : functional reach test ; rat : 
 robot - assisted therapy the average semg value of vm , frt , and the maximum and average extensor strengths of the 
 knee joint isokinetic movement increased significantly .
however , the changes the maximum and average semg values of vl , the maximum 
 semg values of vm and tug were not significant .
according to the results , the walking ability , balance ability and the extensor strength of 
 the knee joint were improved by the rat treatment , and the average semg value of the vastus 
 medialis muscle significantly increased .
the reason for these results is that robotic walking training enabled the bilateral lower 
 limbs to perform alternative and circulatory movements , which can effectively adjust lower 
 limb movement after acl reconstruction . in this manner , walking ability can also be 
 improved .
there was no significant change in the semg value of the vastus lateralis , presumably 
 because weakness of knee joint muscle is often observed in the vastus medialis , which is the 
 first muscle to show weakness among the quadriceps muscles15 .
many studies have attempted to suggest the best angular velocity 
 during isokinetic exercise to selectively strengthen the vastus medialis16 .
however , compared to the vastus 
 lateralis , the vastus medialis was clearly enhanced by rat training .
these results suggest that walking ability and muscle strength can be improved by robotic 
 walking training as a long - term intervention .
future studies with a control group and more 
 subjects are needed to investigate the effects of different walking models using rat after 
 long - term intervention for patients with acl reconstruction .
 [ purpose ] the aim of this study was to examine the long - term interventions effects of 
 robot - assisted therapy rehabilitation on functional activity levels after anterior 
 cruciate ligament reconstruction . [ subjects and methods ] the subjects were 8 patients ( 6 
 males and 2 females ) who received anterior cruciate ligament reconstruction . the subjects 
 participated in robot - assisted therapy lasting for one month . 
 the timed up - and - go test , 
 10-meter walk test , functional reach test , surface electromyography of the vastus 
 lateralis and vastus medialis , and extensor strength of isokinetic movement of the knee 
 joint were evaluated before and after the intervention . 
 [ results ] the average value of the 
 of vastus medialis emg , functional reach test , and the maximum and average extensor 
 strength of the knee joint isokinetic movement increased significantly , and the time of 
 the 10-meter walk test decreased significantly . 
 [ conclusion ] these results suggest that 
 walking ability and muscle strength can be improved by robotic walking training as a 
 long - term intervention . 