cerebral palsy is a disease of permanent disabilities with permanent problems related to 
 engaging in activities , postural development , and movement resulting from a nonprogressive 
 lesion in an immature brain that occurs before , during , or after birth1 .
therefore , rehabilitation for children with cerebral palsy 
 has traditionally focused on improving the gross motor skills , strengthening of the muscles , 
 and the use of assistive equipment .
however , current neurological rehabilitation focuses on 
 motor learning by utilizing the concept of neuroplasticity2 .
smaniaet al . reported that repetitive gait training was more 
 effective in improving gait speed , stride length , and joint kinematics than traditional 
 physical therapy in children with cerebral palsy3 .
traditional treadmill gait training , which is one type of commonly 
 used repetitive gait training , improves motor learning and lower limb muscle strength , 
 activates locomotor control systems , and enables children to experience the habits and 
 task - specific gait behaviors that affect functional ability4 , 5 . among the possible 
 training elements , backward gait training on a treadmill occurs in a direction that is 
 opposite to forward gait training , but is regulated by the same central pattern generator 
 mechanism ; therefore , it might be presented as a therapeutic intervention method for 
 improving forward gait ability6 .
unlike 
 forward gait , backward gait has no heel contact during the early stance phase ; consequently , 
 it might minimize stress to the lower limb joints by avoiding rapid weight load during the 
 early phase7 .
in addition , motor units are 
 recruited more effectively8 , and adequate 
 stress is provided to the lower limb joints , increasing the strength and balance ability of 
 muscles near the knee joints9 .
one study , 
 showed that when healthy school - aged children engaged in backward gait , their sense of 
 balanceimproved10 ; moreover , backward 
 gait at the same speed consumed more oxygen , increased metabolic rate , and enhanced 
 cardiovascular function compared to forward gait11 . recent research on children with cerebral palsy showed that 
 backward gait training positively affected children with spastic hemiplegia12 . while research on backward gait training 
 on a treadmill is ongoing13 , only a few 
 studies have examined the effects of gait direction and changes in the treadmill gradient in 
 children with cerebral palsy . therefore , this study aimed to provide basic data to determine 
 variables of gait training intensity on a treadmill by comparatively analyzing forward and 
 backward gait at different treadmill gradients ; the effect on muscle activity of the paretic 
 side lower limbs was evaluated during the stance phase .
nineteen subjects diagnosed with spastic cerebral palsy were selected for this study ( table 1table 1.general characteristics of subjectsmeasurementpre - testage ( years)17.4  4.5gender ( male / female)12/7height ( cm)159.4  8.6weight ( kg)52.1  12.2gmfcs ( i / ii / iii)(16/0/3)*p<0.05 ) . the criteria for selection of the subjects were as follows : gross motor 
 function classification system ( gmfcs ) levels i  iii ; age 10 to 25 ; modified ashworth scale 
 ( mas ) levels 12 ; ability to walk 10  m backward using an assistive gait device ; and ability 
 to follow verbal instructions .
the criteria for exclusion are as follows : inability to walk independently walk ; 
 neurological or orthopedic surgery related to cerebral palsy within the prior six months ; 
 uncontrollable seizures , or visual , auditory , or perception difficulty .
all the subjects understood the purpose of this study and gave written consent before 
 participating , according to the ethical standards of the helsinki declaration .
ethical 
 approval was given by the local university or hospital research ethics boards.all the 
 subjects engaged in forward and backward gait at a self - selected pace .
the treadmill 
 gradients were 0% , 5% , 10% , and 15% , and the subjects walked for 30 seconds at each 
 gradient .
whenever the gradient changed , the subjects rested for one minute in order to 
 prevent muscle fatigue . in this study , gradient means the percentage of vertical distance 
 against the horizontal distance .
for example , a 10% gradient means climbing 10  m while 
 walking 100  m. in order to identifythe muscle activity of the lower limbs during the stance 
 phase of forward and backward gait , wireless surface electromyography ( emg ) ( telemyo dts , 
 noraxon inc .
the electrodes were attached to the rectus femoris , biceps femoris , tibialis anterior , and 
 lateral gastrocnemius , which play an important role in gait . for subjects
whose lower limbs 
 and upper and lower extremities were paralyzed , the electrodes were attached to their 
 dominant paretic lower limb .
the areas where the electrodes were attached were determined 
 using the surface electromyography for the non - invasive assessment of muscles protocol14 .
the electrodes were attached at the 
 middle area of the belly , where the muscles are most activated , through manual muscle 
 testing .
the amplified waveforms 
 were filtered with a band pass filter set at 40400  hz and a notch filter set at 60  hz for 
 removal of noise .
all the emg signals collected in this way were standardized using the root 
 mean square ( rms ) . in order to obtain average values for the muscle activity of the paretic 
 lower limb during the stance phase , six gait cycle amplitude ,
whose signal was correctly 
 made in the footswitch while walking for 30 seconds at the angle gradient , was transformed 
 into aneffective value , and the obtained average values were comparatively analyzed . 
 considering that the subjects were childrenwith cerebral palsy , this study selected and used 
 standardized reference voluntary contraction ( rvc ) values .
the reference values of rvc were 
 measured with a standing posture as the standard , and the average values of activity 
 measured during the stance phase while walking on an inclined treadmill were expressed as 
 rates .
to identify the difference 
 between forward and backward walking on a treadmill , a paired t - test was used . to evaluate 
 muscle activity according to the four different treadmill inclines , statistical analysis 
 with repeated one - way analysis of variance ( anova )
changes in lower limb emg signals occurred according to changes in the treadmill gradient 
 during the forward and backward gait stance phase . during the forward gait stance 
 phase , based on the treadmill gradients of 0% , 5% ,
10% , and 15% , the lower limb emg signal ( % 
 rvc ) was not statistically significantly different for the tested muscles ( p>0.05 ) ( table 2table 2.comparison of muscle activity between each inclined treadmill during forward 
 walkingmuscle0%5%10%15%fwrf235.2  145293  242.2317.1  305.4325.2  314.1bf259.1  128.4256.9  118.5261.6  138.9265.9  143.4ta217.6  106.5216  97.4238.1  128.2231.7  111.4lgm412.8  600.9290  206.1314.7  242.5343.4  315.8 ) . during the backward gait stance phase , based on gradients of 0% , 5% ,
10% , 
 and 15% , the muscle activity of the lower limbs was significantly different only for the 
 rectus femoris ( p<0.05 ) , and no significant difference was found for the biceps femoris , 
 tibialis anterior , and lateral gastrocnemius ( p>0.05 ) ( table 3table 3.comparison of muscle activity between each inclined treadmill during backward 
 walkingmuscle0%5%10%15%bwrf344.5  249.1386  352.5436.3  402.3 * 509.3 
830.6bf254.3  148.4224.9  107.8254  128.2248.4  131.8ta276.3  170.5289.2  243.4276.3  170.2284.4  226.6lgm266.7  131.5293.2  167.3282  148.4279.9  165.7*p<0.05 ) .
the lower limb emg signals for forward and backward gait , were compared , based on changes 
 in the treadmill gradient . according to the results of the paired t - test comparing the emg 
 signals for forward and backward gait ,
the rectus femoris showed a statistically significant 
 difference at 0% , 5% , and 10% ( p<0.05 ) , but there was no significant difference at the 
 15% gradient ( p>0.05 ) .
however , the backward gait tended to have higher emg signals than 
 the forward gait .
the tibialis anterior activity showed a statistically significant 
 difference at the 10% gradient ( p<0.05 ) , but no significant difference was observed at 
 the other gradients ; however forward gait tended to exhibit higher emg signals than backward 
 gait .
there was no significant difference between forward and backward gait at all treadmill 
 gradients for the biceps femoris and lateral gastrocnemius ( p>0.05 ) .
this study was conducted in order to examine the effect that treadmill gradient and gait 
 direction had on lower limb muscle activity in children with spastic cerebral palsy , and to 
 provide basic data for determining appropriate gait training for these children .
no 
 significant difference in lower limb muscle activity was found based on changes in treadmill 
 gradients during the forward gait stance phase ; however , muscle activity had a tendency to 
 increase in the rectus femoris , biceps femoris , and tibialis anterior . according to lay et 
 al .
, when a person climbs a slope , the moment of force of the hip joint extensor increases , 
 and this increased counterforce of the hip joint extensor increases the muscle activity of 
 the knee joint extensor15 .
previous 
 research has shown that the tibialis anterior had eccentric control of the load during the 
 early stance phase ; therefore , the load delivered from the increase in the gradient also 
 increased , and the activity of the tibialis anterior increased16 .
the present study also showed a similar trend , but failed 
 to obtain a significant value because the number of subjects in the study sample was small . 
 in backward gait ,
only activity in the rectus femoris significantly increased based on the 
 increase in the treadmill gradient . engaging in an early knee flexing exercise during the 
 supporting stage of backward gait
is related to the role of weight absorption during the 
 process of supporting the body after landing ; therefore , backward gait can increase the 
 strength of the quadriceps femoris muscle while decreasing the load of the knee joints 
 during the stance phase .
the present studyobtained the same results17 . accordingly , this could be a therapeutic method for 
 patients with hemiplegia accompanying hyper - extension .
changes in muscle activity according 
 to changes in the gradient mean that the changes in the joint moment that occur in the lower 
 limbsbased on increases in the gradient are different ; therefore different motor control 
 strategies are needed .
for example , as the gradient changes , the moment in each joint 
 changes and the tensile force of the golgi tendon organ changes ; thus , information from the 
 peripheral nerves enters the control system , triggering sufficient muscle activity of the 
 lower limbs for a given task15 , 18 .
previous studies comparing forward and backward gait have 
 shown that the maximum extension muscle strength and activity tended to increase more after 
 backward than after forward gait training19 .
the reason for this is that , during forward gait , the 
 gastrocnemius is the driving force , but during backward gait , the rectus femoris , a knee 
 extensor muscle , acts as the driving force17 . in the present study ,
less muscle activity occurred in the lateral 
 gastrocnemius during backward than during forward gait forall of gradients , but the activity 
 of the tibialis anterior showed an opposite trend .
this is thought to be because during 
 backward gait , the gastrocnemius decreases ankle movement during the early stance phase , and 
 the tibialis anterior adjusts ankle movement with eccentric contraction20 .
in addition , the results of the present study are 
 consistent with findings presented in previous research , which found that during backward 
 gait , the gastrocnemius no longer acts as a driving force21 . furthermore , as the treadmill gradient increases , the movement of 
 the lower limb joints increases , which requires anincrease in lower limb muscle activity . 
 moreover , a study that compared the biomechanical and physiological advantages of forward 
 and backward gait , reported that the muscle activity in backward gait was higher than in 
 forward gait , and the muscle activity of a longer lower limb was able to achieve higher 
 strength22 . in a study that compared 
 the activity of the quadriceps femoris based on exercise direction with treadmill gradients 
 of 0% , 5% , and 10% ,
han reported significant muscle activity differencesbased on exercise 
 direction , which is consistent with the results of the present study23 .
based on these results , backward gait training might be proposed as a method to minimize 
 load to the knees and increase muscle strength resulting from isometric and uniaxial 
 contraction of the quadriceps femoris during the stance phase . by increasing the treadmill 
 gradient , it might be possible to adjust gait training to establish an appropriate intensity 
 for children with cerebral palsy .
first , the number of 
 cerebral palsy childrenin the sample was small and it is difficult to generalize the 
 results .
second , three - dimensional gait analysis was not performed ; therefore , changes in 
 the location of the joints were not known .
future research is necessary to examine joint 
 location and plantar pressure changes in a greater number of spastic cerebral palsy children 
 at different treadmill gradients .
 [ purpose ] this study investigated the effects of forward and backward walking using 
 different treadmill incline positions on lower muscle activity in children with cerebral 
 palsy , to provide baseline data for gait training intensity . 
 [ subjects and methods ] 
 nineteen subjects with cerebral palsy walked forward and backward at a self - selected pace 
 on a treadmill with inclines of 0% , 5% , 10% , and 15% . 
 activation of the rectus femoris , 
 biceps femoris , tibialisanterior , and lateral gastrocnemius was measured using surface 
 electromyography during the stance phase . 
 [ results ] as treadmill incline increased during 
 forward walking , muscle activation of the paralyzed lower limbs did not significantly 
 change . however , as treadmill incline increased during backward walking , rectus femoris 
 activation significantly increased and a significant difference was found between 
 treadmill inclines of 0% and 10% . 
 a comparison of backward and forward walking showed a 
 significant difference in rectus femoris activation at treadmill inclines of 0% , 5% , and 
 10% . 
 activation of the tibialis anterior was only significantly higher for backward 
 walking at the 10% gradient . 
 [ conclusion ] backward walking may strengthen the rectus 
 femoris and tibialis anterior in walking training for cerebral palsy . 
 gradient adjustment 
 of the treadmill can be used to select the intensity of walking training . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION