lumbar stability is a important point that enables movement of the limbs while maintaining 
 of the spine upright under postural change and load1 .
muscles that contribute to lumbar stability include the transversus 
 abdominis , internal oblique , external oblique , quadratus lumborum , the multifidus of the 
 posterior trunk , and the pelvic floor muscles2 .
in particular , the multifidus and the transversus abdominis are 
 activated earlier than the other muscles when the human body moves and adjusts the balance 
 of the trunk .
similarly , the bilateral internal oblique muscles are important for 
 maintaining lateral stability and the bending ability of the spine . prior research on lumbar 
 stability has been conducted with the aim of understanding how to strengthen the spine 
 through the deep muscles such as the transversus abdominis and multifidus and different 
 exercise tools including mattresses , balls , dumbbells , balance pads , and diverse postures 
 such as the supine or prone positions that are used at the beginning of the lumbar flexion 
 exercise have been used3 .
squat exercises evenly develop upper body as well as lower body muscles4 and may be done anywhere and at anytime . 

this type of exercise is used for improving physi cal performance in many sports and may be 
 effectively used in rehabilitation programs after an operation5 .
squat exercises have great merit , but an unstable posture when this 
 type of exercise is performed damage the lower back and exert pressure on the knees6 .
however , wall squat exercises are safe , 
 without any possibility of doing harm to the lumbar vertebrae or knees because the squats 
 are performed with the body weight on the wall , making it easy for beginners to conduct this 
 exercise . as a result
, modified wall squat exercises were used in this study with the aim of 
 improving lumbar stability rather than strengthening the lower body muscles , and this 
 exercise included motions to strengthen the neck and improve shoulder stability .
the aim of 
 this study was to compare modified wall squat exercises that may be simply conducted without 
 the help of tools or equipment and without any limitation in space , with bridge exercise an 
 ordinary lumbar stability exercise , for lumbar stability improvement .
thirty normal adults were randomly allocated either to a bridge exercise group ( beg : 1 
 male , 14 female ; the experimental group ) or to a modified wall squat exercise group ( mwseg : 
 1 male , 14 female ; the control group ) . those with muscle , skeletal , or neurological 
 problems , those who felt pain in the lumbar or pelvic areas , and those who could not perform 
 the bridge exercise or wall squat due to pain in the knees or ankles were excluded . 

sufficient explanation of this study s intent and the overall purpose was given , and 
 voluntary consent to participate in this study was obtained from all of the subjects . the 
 meansd age , height , and weight of beg were 20.80.3  years old , 161.86.6  cm , and 
 55.39.3  kg , respectively ; and the meansd age , height , and weight of mwseg were 
 20.70.3  years old , 162.94.5  cm , and 56.39.7  kg , respectively .
analysis of group 
 difference in gender was made using the  test , and analyses of group difference 
 in age , height , and weight were made using the independent t - test .
the above factors were 
 not significantly different ( p>0.05 ) , therefore the two groups were considered 
 homogenous .   modified wall squat exercise the subjects conducted bridge exercises using the abdominal drawing - in method and modified 
 wall squat exercises on stable ground .
the abdominal drawing - in method aims to contract the 
 transversus abdominis and internal oblique , thereby inducing concurrent contraction of the 
 muscles and reducing excessive lumbar lordosis or anteversion of the pelvis that may occur 
 during bridge exercises or modified wall squat exercise1 . for the bridge exercise
, subjects flexed their knee joints to 90 
 degrees , spread both arms by about 30 degrees , and placed both hands on the chest .
the 
 subjects placed both feet at shoulder - width apart and placed both feet parallel on the 
 ground .
the head and the neck were maintained straight , and the eyes looked at the ceiling . 

the subjects raised the pelvis according to the instruction  raise the hips ,  maintained the 
 posture for 15 seconds according to the instruction 
maintain ,  then lowered the pelvis , and 
 took a rest for 5 seconds according to the instruction  lower the hips .
 ten repetitions of 
 this process were considered one set , and the subjects performed a total of 10 sets7 .  
measurement of tra & io for the modified wall squat exercises , the subjects stood against a wall , spread both legs 
 shoulder - width apart , and stood at a distance of about a foot from the wall . with fingers 
 spread out , one hand was held with the palm end upward from the chest , while the finger ends 
 of the other hand around the belly were held downward , and pulled the chin was pulled in 
 pushing the head toward the wall .
, the 
 soles of the feet did not leave the ground , the knees were flexed up to a 90 degree angle 
 where they remained for 5 seconds , and then the knees were extended back to a 10 degree 
 angle which was maintained for 3 seconds .
this was counted as one motion was a process , and 
 10 motions were considered one set .
the subjects took a rest for 15 seconds and conducted 
 this process again for a total of 10 sets .
the subjects conducted bridge exercises and 
 modified wall squat exercises three times per week , 30 minutes per day , for a total of 6 
 weeks . in order to examine changes in muscle thickness of the trunk and the abdomen of the 
 participants , this study used ultrasonography ( mysonou5 , samsung medison , korea ) with a 
 12  mhz linear probe . in order to ensure measurement at the same location each time ,
the 
 probe was placed transversely on the top of the iliac crest , moved toward the center of the 
 abdomen , and the screening was stopped when the external oblique , internal oblique , and 
 transversus abdominis were all shown .
the thicknesses of the internal oblique and 
 transversus abdominis were measured at a point 13  mm distal from the point where the fascias 
 of the internal oblique and the transversus abdominis met8 . for the measurement of the multifidus
, the subjects lay in the 
 prone position , and the probe was perpendicularly placed on the fourth lumbar vertebra on 
 the left transverse process .
the thickness from the transverse process to the superficial 
 muscle was measured9 ( fig .
the 
 contractibility of tra was evaluated using a pressure biofeedback unit ( pbu , chattanooga 
 group , australia ) .
the pbu is an inelastic sack that can be inflated and is connected to a 
 pressure gauge .
it is a simple device that monitors and records changes in pressure during 
 the movement of the lumbar pelvis .
the size of the sack is 16.724.0  cm , and it has a 
 measurement range of 0200 mmhg .
excessive changes in pressure signify that movement of the 
 lumbar pelvic area is not regulated .
for sls measurement , the subjects lay in the prone 
 position , and the pbu was placed on the midpoint of the bilateral anterior superior iliac 
 spines ; and the baseline pressure was set to 70 mmhg . the subjects pulled in their lower 
 abdomens to the maximum level without moving the lumbar vertebrae or hips , lowering the 
 pressure , and maintained this position for 10 seconds .
the change in pressure was recorded . 
 in order to measure dynamic lumbar stability ( dls ) , the subjects performed the bent knee 
 fall out ( bkfo ) , as described by comerford and mottram10 .
for the measurement of bkfo , the subjects lay in the supine 
 position , and the pbu was placed vertically below the lumbar spine 2  cm from the posterior 
 superior iliac spines . in order to minimize the sway of the trunk ,
folded towels of the same 
 height were placed on both sides of the pbu .
the 
 hip and the knee of one leg were bent , and the feet were attached to the ground abducted by 
 about 45 degrees , then moved back to the original posture .
the data were analyzed using spss 12.0 ko ( spss , chicago , il , usa ) , and are presented as 
 average and standard deviations .
the paired t - test was used to test the significance of 
 changes in each group , and the independent t - test was used to test the significance of 
 differences between the two groups .
* p<0.05 ; beg , bridge exercise group ; mwseg , modified wall squat exercise group ; 
 tra , transversus abdominis ; io , internal obliquus abdominis ; sls , static lumbar 
 stability ; dls , dynamic lumbar stability the comparison of the pre - intervention and post - intervention measures of beg and mwseg 
 revealed statistically significant differences in tra and io of both groups ( p<0.05 ) 
 ( table 1 ) . regarding the changes between pre- 
 and post - intervention
, there were no statistically significant differences between the two 
 groups ( p>0.05 ) ( table 2 ) .
this study compared the effects of bridge exercises and modified wall squat exercises using 
 an abdominal drawing - in method on deep abdominal muscle thickness and lumbar stability . 

prior research has shown that the abdominal drawing in method is effective at activating the 
 abdominal muscles , in particular , the transversus abdominis2 . stevens et al . reported that when subjects conducted bridge 
 exercises in the neutral position , abdominal muscle activity increased but multifidus 
 activity was not significantly different11 .
in which 30 lumbar pain patients and 30 
 average subjects completed abdominal drawing - in exercises that contracted the transversus 
 abdominis , observed that the thickness of the transversus abdominis increased in normal 
 subjects and lumbar pain patients who conducted abdominal drawing - in exercise contracting 
 the transversus abdominis12 . in their 
 study , the subjects in a quadruped position alternately stretched the upper and lower limbs 
 in a quadruped position and ultrasonography was used to measure the thickness of the 
 transversus abdominis .
the result of the present study was similar to bridge exercises and 
 modified wall squat exercises increased the thicknesses of the transversus abdominis ( tra ) 
 and internal oblique ( io ) of the normal subjects but did not increase that of the 
 multifidus .
this is probably because bridge exercises and modified wall squat exercises 
 using an abdominal drawing - in method increase abdominal muscle activity and minimize 
 compensation actions such as lumbar lordosis , by relatively reducing the actions of the 
 erector spinae and the multifidus .
according to the comparison of the pre- and post - intervention measures of beg and mwseg , 
 there were statistically significant differences in only tra and io in both groups . 

regarding changes between pre- and post - intervention , there were no statistically 
 significant differences between the two groups .
these results show that the bridge exercise 
 and modified wall squat exercise on stable ground affected the development of the tra and io 
 muscles , but did not have an effect on the other muscles . in particular ,
although bridge 
 exercises and modified wall squat exercises have the same effect on the development of the 
 tra and io muscles , the bridge exercise requires a space to lie and a mattress .
however , the 
 modified wall squat exercises enable lumbar stability exercise against a wall and may be 
 conveniently performed anytime , anywhere . accordingly
, the researcher hopes that the 
 modified wall squat exercise will be utilized together with bridge exercises in home 
 training for patients who need lumbar stabilization exercises .
   [ purpose ] the purpose of this study was to compare the effects of bridge exercises 
 applying the abdominal drawing - in method and modified wall squat exercises on deep 
 abdominal muscle thickness and lumbar stability . 
 [ subjects ] a total of 30 subjects were 
 equally divided into an experimental group and a control group . 
 [ methods ] the experimental 
 group completed modified wall squat exercises , and the control group performed bridge 
 exercises . 
 both did so for 30 minutes three times per week over a six - week period . 
 both 
 groups transversus abdominis ( tra ) , internal oblique ( io ) , and multifidus muscle 
 thickness were measured using ultrasonography , while their static lumbar stability and 
 dynamic lumbar stability were measured using a pressure biofeedback unit . 
 [ results ] a 
 comparison of the pre - intervention and post - intervention measures of the experimental 
 group and the control group was made ; the tra and io thicknesses were significantly 
 different in both groups . 
 [ conclusion ] the modified wall squat exercise and bridge 
 exercise affected the thicknesses of the tra and the io muscles . while the bridge exercise 
 requirs space and a mattress to lie on , the modified wall squat exercise can be 
 conveniently performed anytime . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION