lumbar degenerative kyphosis ( ldk ) is a common cause of lumbar spinal deformity in asian 
 women aged 40  years and older .
it is characterized by sagittal imbalance , a stooped posture 
 and chronic low back pain ( lbp ) . associated with ldk
is a loss of the normal lumbar spinal 
 lordosis1,2,3 . marked atrophy of lumbar 
 extensors and degenerative changes in the lumbar spine are hallmarks of this condition . it 
 is postulated that endemic lifestyles such as prolonged crouching , often required of 
 agricultural workers , may be a factor in the development of ldk1,2,3 . in studies utilizing computed tomography ( ct ) and magnetic 
 resonance imaging ( mri ) , extensive degenerative atrophy and fatty infiltration of lumbar 
 extensor muscles have been reported1,2,3 . 

moreover , in a state of sagittal imbalance , kyphosis or loss of lordosis of the lumbar spine 
 can lead to lbp and various spinal disorders4,5,6,7 .
lbp is known to arise from multiple factors , including the loss of lumbar spinal 
 stability8,9,10,11 .
if a state of lumbar instability is not appropriately resolved , 
 chronic recurrent lbp might occur12 . 

patients with lbp do not sufficiently activate the deep lumbar stabilizing muscles , such as , 
 the lumbar multifidus ( lm ) , transversus abdominis ( tra ) , and obliquus internus ( oi ) muscles , 
 which are essential for lumbar spinal stability13,14,15 .
therefore , specific exercises for lumbar stabilizing muscles are 
 essential in the rehabilitative strategy for patients with lbp16,17,18,19,20 .
however , traditional exercises for deep lumbar 
 stabilizing muscles tend to be laborious and time intensive for therapists and patients . 
 since deep lumbar stabilizing muscles are smaller in patients with chronic lbp and contain a 
 higher proportion of fat3 , affected 
 individuals find it more difficult to sufficiently activate these muscles .
neuromuscular electrical stimulation ( nmes ) is a form of lumbopelvic stabilizing 
 rehabilitation that is being increasingly used to reinforce muscle strength and prevent 
 muscle atrophy18,19,20,21,22,23,24,25 .
this technique has also shown promise in training of the deep 
 lumbar stabilizing muscles22,23,24,25 .
in addition , muscle activation by nmes has been reported 
 to be significantly related to clinical improvements in patients with lbp24 , 26 .
however , no report to date has been issued on the effects of nmes on 
 the deep lumbar stabilizing muscles of ldk patients , and few studies have attempted to 
 define the optimal protocol for the stimulation of deep lumbar stabilizing muscles by 
 nmes . in this study ,
the ability of nmes to stimulate the deep lumbar stabilizing muscles of ldk 
 patients was investigated , using real - time ultrasound imaging ( rusi ) .
twenty patients with symptomatic sagittal imbalance due to ldk , who visited the 
 rehabilitation department of yeungnam university hospital , were recruited ( 19 females , 1 
 male , overall mean age 66.22  6.55  years , range 5474 years ) .
the selected patients 
 exhibited the characteristic clinical features of ldk , that is , a stoop with walking 
 difficulties , an inability to lift heavy objects , difficulty walking on an inclined plane , 
 and the need for elbow support when standing for any length of time . whole - spine lateral 
 views showed loss of lower lumbar lordosis resulting in retroversion of the pelvis with 
 thoracolumbar lordosis compensating for sagittal imbalance .
patients with a history of 
 osteoporotic compression fracture , spine surgery , spinal disease ( trauma , tumor , scoliosis , 
 scheuermann s kyphosis , or stenosis ) , hip joint disease , or contraindications for nmes 
 ( pacemaker , edema , paresthesia , thromboembolism etc . ) were excluded .
the participants were 
 provided with comprehensive oral and written information about all aspects of this study , 
 and all provided their written consent to participation .
this study was conducted 
 prospectively and the institutional review board of our hospital approved the study 
 protocol .
abdominal electrical stimulation was delivered through a set of 4 hydrogel surface 
 electrodes ( 5  cm  5  cm ) located on both sides of the anterolateral abdominal wall .
two 
 surface electrodes were placed on the right and two on the left sides .
the reference points 
 were located 1  cm superior to the iliac crests on the mid axillary lines .
abdominal 
 stimulation points were located 2  cm superior and 2  cm medial to the anterior superior iliac 
 spines ( fig .
1.sites of stimulation 
 used on the abdominal wall and lumbar paraspinal region(a ) abdominal wall ( frontal view ) , ( b ) abdominal wall ( lateral view ) , ( c ) lumbar 
 paraspinal regions : stimulation electrode , r : reference electrode7 .
lumbar electrical stimulation was 
 also delivered through a set of 4 hydrogel surface electrodes ( 5  cm  5  cm ) positioned 
 bilaterally at an inter - electrode spacing of ~2  cm on a cross line drawn on the l45 
 interspinous process ( fig .
stimulation pulses were generated using a portable 
 research - stimulator ( cmmx-001a ; cybermedic corp .
, republic of korea ) , which delivered a 
 constant current and a symmetrical biphasic waveform .
bi - phasic symmetrical pulses of 200 s 
 with an interpulse delay of 100 s were employed .
these pulses were delivered via the four 
 surface electrodes at a frequency that produced tetanic isometric contractions of the 
 targeted muscles ( 50  hz ) .
the overall contraction - relaxation cycle used was as follows : ramp 
 up for 1 second , contraction for 8 seconds , and ramp down for 1 second followed by 
 relaxation for 10 seconds .
the subjects were instructed to use the unit at an intensity that elicited 
 maximum muscle contraction without discomfort , that is , no burning sensation or severe 
 tetanic pain .
the mean current intensity was 45.39  10.24 ma for the abdominal muscles , and 
 58.34  12.97 ma for the lumbar muscles .
each muscle was evaluated during three different 
 nmes protocols : protocol a , stimulation of abdominal muscles , protocol b , stimulation of 
 lumbar muscles ; and protocol a+b , concurrent stimulation of abdominal and lumbar 
 muscles .
sites of stimulation 
 used on the abdominal wall and lumbar paraspinal region ( a ) abdominal wall ( frontal view ) , ( b ) abdominal wall ( lateral view ) , ( c ) lumbar 
 paraspinal region s : stimulation electrode , r : reference electrode a rusi ( logiq 6 expert , ge healthcare , uk ) unit was used to measure changes in the 
 abdominal and lumbar muscle [ tra , oi , obliquus externus ( oe ) , and lm ] thicknesses during 
 nmes of each protocol . to assess abdominal muscles , with subjects comfortably positioned 
 supine with a pillow placed under the knees , a 5  mhz curvilinear ultrasound probe was placed 
 transversely across the abdominal wall along the line midway between the inferior angle of 
 the rib cage and the iliac crest .
the medial edge of the probe was placed approximately 
 10  cm from the midline , and , its position was adjusted to ensure that the medial edge of the 
 tra was ~2  cm from the medial edge of the ultrasound image when the subject was relaxed 
 ( fig .
2.thicknesses of abdominal 
 muscles during nmesthree vertical lines were drawn : one at the midline of the image and two 1  cm 
 ( adjusted for scale ) either side of the midline.oe : obliquus externus muscle , oi : obliquus internus muscle , tra : transversus 
 abdominis muscle)29 .
the location of the probe was 
 marked to ensure its identical placement for all measurements .
static ultrasound images were 
 captured at rest and again when maximum nmes stimulation had been reached . during image 

capture at rest , the subjects were instructed to breathe normally and evenly and an image 
 was captured at the end of exhalation . during stimulation image capture ,
preliminary analysis of the 
 results indicated that the right and left sides contracted in similar ways , and thus , 
 further analysis was carried out using right side images . to evaluate the lm ,
the subjects 
 were placed prone , with the abdomen supported as needed to ensure no more than 10 of lumbar 
 lordosis , and then instructed to breathe normally and evenly .
static rest images were 
 captured at the end of exhalation ( fig . 3fig .
3.thickness of the lumbar 
 multifidus muscle during nmesthe lumbar multifidus muscle thickness was measured at the distance between the 
 posterior - most portion of the l4/l5 facet joint and the fascial plane between the 
 muscle and subcutaneous tissue.sm : superficial lumbar multifidus muscle , dm : deep lumbar multifidus muscle ) , and static ultrasonic images of the lm muscle were taken during each nmes 
 stimulation protocol .
all the above tasks were performed three times , and the average of the 
 three measurements was used in the analysis .
thicknesses of abdominal 
 muscles during nmes three vertical lines were drawn : one at the midline of the image and two 1  cm 
 ( adjusted for scale ) either side of the midline .
oe : obliquus externus muscle , oi : obliquus internus muscle , tra : transversus 
 abdominis muscle thickness of the lumbar 
 multifidus muscle during nmes the lumbar multifidus muscle thickness was measured at the distance between the 
 posterior - most portion of the l4/l5 facet joint and the fascial plane between the 
 muscle and subcutaneous tissue .
sm : superficial lumbar multifidus muscle , dm : deep lumbar multifidus muscle stored images were analyzed using ultrasound image measurement software .
on abdominal 
 images , a grid was placed over the images and the thicknesses of oe , oi , and tra muscles 
 were measured at three sites , that is , at the image midline and at 1  cm either side of the 
 midline .
cursors were placed on the superficial and deep boundaries of the muscles at the 
 edges of the hypoechoic regions representing the locations of fascial separations between 
 muscles29 .
on lumbar images , the 
 thickness of the lm muscle was measured between the posterior - most portion of l4/l5 facet 
 joints and the fascial planes between the muscles and subcutaneous tissues30 .
the average of the three measurements was 
 used in the analysis and the effects of nmes were investigated using the changes in 
 thickness between rest and during nmes ( figs .
4.comparison of the 
 thicknesses of lumbar multifidus muscles(a ) at rest , ( b ) during protocol b ; stimulation of lumbar 
 muscles , ( c ) during protocol a+b ; concurrent stimulation of abdominal and 
 lumbar muscles , and ( d ) during protocol a ; stimulation of abdominal 
 musclessm : superficial lumbar multifidus muscle , dm : deep lumbar multifidus muscle 
 and 5fig .
( a ) at rest , ( b ) protocol a ; stimulation of abdominal 
 muscles , ( c ) protocol a+b ; concurrent stimulation of abdominal and lumbar 
 muscles , ( d ) protocol b ; stimulation of lumbar muscles .
oe : obliquus externus muscle , oi : obliquus internus muscle , tra : transversus 
 abdominis muscle ) .
( b ) during protocol b ; stimulation of lumbar 
 muscles , ( c ) during protocol a+b ; concurrent stimulation of abdominal and 
 lumbar muscles , and ( d ) during protocol a ; stimulation of abdominal 
 muscles sm : superficial lumbar multifidus muscle , dm : deep lumbar multifidus muscle comparison of the 
 thicknesses of three abdominal muscles . ( a ) at rest , ( b ) protocol a ; stimulation of abdominal 
 muscles , ( c ) protocol a+b ; concurrent stimulation of abdominal and lumbar 
 muscles , ( d ) protocol b ; stimulation of lumbar muscles .
oe : obliquus externus muscle , oi : obliquus internus muscle , tra : transversus 
 abdominis muscle statistical analysis was performed using the statistical package for the social sciences 
 ( spss ) version 18.0 ( spss , chicago , il , usa ) .
the paired t - test was used to determine the 
 significances of thickness differences at rest and during nmes for each muscle ( lm , oe , oi 
 and tra ) , and one - way analysis of variance ( anova ) and the kruskal - wallis test were used to 
 analyze differences between the a , b and a+b protocols for each muscle .
when a significant 
 difference was found between groups , tukey s post - hoc test was used for assess pair - wise 
 comparisons .
the mean age , height , weight , and body mass index ( bmi ) of the twenty participants were 
 66.22  6.55  years , 157.92  8.66  cm , 57.94  6.75  kg , and 23.27  2.42 
significant thickness changes in the superficial and deep lms were observed during nmes 
 during all three protocols ( p < 0.05 ) .
significant thickness changes in abdominal muscles 
 ( oe , oi , and tra ) were also observed during nmes during protocols a and a+b ( p < 0.05 ) , 
 but not during protocol b ( table 1table 1.thicknesses ( mm ) at rest and during nmesmusclerestnmes protocolaba+bsm12.7 ( 2.1)13.1 ( 1.6)13.9 ( 2.0)13.9 ( 1.8)dm11.2 ( 1.6)11.4 ( 2.1)12.2 ( 2.0)12.3 ( 2.3)oe5.2 ( 2.1)7.3 ( 2.9)5.5 ( 2.1)7.1 ( 3.0)oi7.8 ( 1.8)9.1 ( 2.1)7.7 ( 1.5)8.8 ( 2.1)tra3.0 ( 0.8)3.7 ( 1.1)3.2 ( 0.7)3.7 ( 1.0)values are means (  standard deviations ) . nmes : neuromuscular electrical stimulation . a : stimulation of abdominal muscles , b : stimulation of lumbar muscles , a+b : 
 simultaneous stimulation of abdominal and lumbar muscles .
sm : superficial lumbar mutifidus muscle , dm : deep lumbar mutifidus muscle , oe : 
 obliquus externus muscle , oi : obliquus internus muscle , tra : transversus abdominis 
 muscle*significantly increased compared to the resting state , p < 0.05 and fig .
a : stimulation of abdominal muscles , b : stimulation of lumbar muscles , a+b : 
 simultaneous stimulation of abdominal and lumbar muscles .
sm : superficial lumbar mutifidus muscle , dm : deep lumbar mutifidus muscle , oe : 
 obliquus externus muscle , oi : obliquus internus muscle , tra : transversus abdominis 
 muscle * significantly increased compared to the resting state , p < 0.05 increases in the thicknesses of the superficial and deep lms during protocol b and a+b were 
 significantly larger than during protocol a ( p < 0.05 ) , but no significant difference was 
 found between protocols b and a+b .
increases in the thicknesses of oe , oi , and tra were 
 significantly greater during protocols a and a+b than during b protocol ( p < 0.05 ) , but 
 no significant difference was found between protocols a and a+b ( table 2table 2.thickness ( mm ) changes from rest induced by nmesmusclenmes protocolstimulation effecta ( a)b ( b)a+b ( c)pabpacpbcsm0.5 ( 1.1)1.2 ( 1.0)1.3 ( 1.1)0.0340.0360.499dm0.3 ( 0.8)1.0 ( 0.9)1.1 ( 1.3)0.0380.0280.494oe2.1 ( 1.7)0.1 ( 0.8)1.9 ( 1.9)0.0020.4690.005oi1.3 ( 1.1)0.2 ( 0.4)1.0 ( 1.2)0.0000.2970.002tra0.7 ( 0.7)0.7 ( 0.7)0.6 ( 0.7)0.0180.4750.034values are means (  standard deviations ) . nmes : neuromuscular electrical stimulation . a : stimulation of abdominal muscles , b : stimulation of lumbar muscles , a+b : 
 simultaneous stimulation of abdominal and lumbar muscles .
sm : superficial lumbar mutifidus muscle , dm : deep lumbar mutifidus muscle , oe : 
 obliquus externus muscle , oi : obliquus internus muscle , tra : transversus abdominis 
 musclesignificant difference among the a , b and a+b protocols ( p < 0.05)p < 0.05 and fig . 5 ) . values are means (  standard deviations ) .
a : stimulation of abdominal muscles , b : stimulation of lumbar muscles , a+b : 
 simultaneous stimulation of abdominal and lumbar muscles .
sm : superficial lumbar mutifidus muscle , dm : deep lumbar mutifidus muscle , oe : 
 obliquus externus muscle , oi : obliquus internus muscle , tra : transversus abdominis 
 muscle significant difference among the a , b and a+b protocols ( p < 0.05 )
this study showed that the deep lumbar stabilizing muscles of patients with ldk were 
 significantly activated by nmes . furthermore
, our results show the protocols b and a+b 
 maximally stimulated the superficial and deep lm muscles , and that protocols a and a+b 
 maximally stimulated the abdominal ( tra , oi and oe ) muscles .
these observations show that 
 the deep lumbar stabilizing muscles ( lm , tra and oi ) were significantly and maximally 
 stimulated by protocol a+b .
previous studies have reported that nmes effectively activates 
 the deep lumbar stabilizing muscles22,23,24,25 , and the results of this study confirm 
 these findings .
all studied lumbar and abdominal muscles , including the deep and superficial 
 muscles , contracted simultaneously during nmes .
these findings suggest that nmes may provide 
 a means of strengthening the deep lumbar stabilizing muscles of patients with ldk .
the 
 possibility of contracting and thereby training the smaller poorly conditioned lumbar 
 stabilizing muscles of patients with ldk is encouraging and may provided an additional 
 avenue for rehabilitation .
several studies have reported that nmes effectively activates the deep lumbar stabilizing 
 muscles23 , 24 , 27 , 28 .
coghlan et al.23 demonstrated a significant increase in tra thickness during 
 belt - type nmes of healthy subjects . in another study by the same authors24
, patients with chronic lbp were found to 
 show significant increases in the thicknesses of tra , oi , and lm during loading tasks after 
 6 weeks of nmes intervention .
baek et al.28 reported that 20 healthy subjects showed significant thickness 
 increases in lm , tra and oi during nmes of the lumbar paraspinal region , and baek et 
 al.27 reported 20 healthy subjects 
 showed significant tra and oi thickness increases during nmes applied to the abdominal wall . 

our results are in agreement with these results and suggest that nmes could be used to train 
 the deep lumbar stabilizing muscles of patients with ldk .
surgical treatment may be considered for ldk patients having difficulties performing 
 activities of daily living due to severe sagittal imbalance . however , as the proportion of 
 elderly individuals in the population has increased , the average age at the time of surgery 
 has also increased , increasing surgical risks and complications . in addition , some patients 
 complain of recurrent chronic lbp and sagittal decompensation related to posture even after 
 surgical correction of kyphotic spinal deformities2 , 
 31
. exercises that help train lumbar 
 stabilizing muscles are typically adopted for conservative treatments of chronic lbp and the 
 correction of kyphotic postures16,17,18,19,20 , 32 . patients with lbp can not sufficiently 
 activate the deep lumbar stabilizers13,14,15 , 
 and thus , extensive lm muscle atrophy is a characteristic of ldk patients33 .
for these reasons , strengthening of the 
 deep lumbar stabilizers of ldk patients is an essential component of treatment .
however , 
 specific exercises for the deep lumbar stabilizers are labor - intensive , are often difficult 
 to maintain , and require repeated patient education sessions by skilled physical therapists . 

stevens et al.34 assessed the effects of 
 stabilization exercises on lm muscle activation using surface electromyography , and found 
 there was no change in lm muscle activation levels .
koumantakis et al.35 investigated the effects of stabilization and general 
 exercises on the lm muscle of lbp patients and also found they had no effect on the lm 
 muscle .
they concluded that isolated lm muscle contraction is difficult to achieve and 
 maintain during exercises34 , 35 .
bilgin et al.22 investigated the effect of an abdominal hollowing exercise on the 
 lm muscle and dound it had no effect on lm muscle activation .
they also reported that 
 patients had difficulty learning and maintaining abdominal hollowing , and concluded that 
 insufficient contraction of the lm muscle probably contributed to their negative result . 

they suggested nmes while performing lumbar stabilizing exercises might help the 
 re - education of lm and tra muscles .
therefore , active utilization of nmes is recommended for 
 the patients with ldk in order to compensate for the limitations of deep lumbar stabilizing 
 exercises in the enhancement of muscle - strengthening effects .
the optimal stimulation protocol for the activation of deep lumbar stabilizing muscles has 
 not been determined . in this study ,
significant thickness changes in lm muscles were found 
 during abdominal wall stimulation ( protocol a ) . this thickness change may be the result of 
 an indirect tensile effect of the lumbar fascia straining during contraction of the 
 abdominal muscles27 , 28 .
baek et al.27 
 reported lm muscle activation without lumbar region activation during nmes applied to the 
 abdominal wall of healthy subjects .
baek et al.28 also reported tra and oi activations during nmes applied to the 
 lumbar region without abdominal wall stimulation in healthy subjects .
therefore , it was our 
 initial expectation that thickness changes in the lm and abdominal ( tra and oi ) muscles 
 during protocol a+b would be greater than during protocols a or b. however , no significant 
 difference was observed between protocols b and a+b , or between a and a+b .
we reason these 
 findings were due to the indirect tensile effect of the lumbar fascia as mentioned 
 above .
the results of this study demonstrate that protocol a+b was effective at activating all the 
 studied deep lumbar stabilizing muscles ( lm , tra and oi ) .
therefore , placing nmes electrodes 
 on the 4 abdominal wall and 4 lumbar regions is suggested for the training of deep lumbar 
 stabilizing muscles of patients with ldk . to our knowledge , no previous report has mentioned 
 the concurrent stimulation of abdominal and back muscles to achieve contractions of the deep 
 lumbar stabilizing muscles
first , the sample size was relatively 
 small , and thus , further larger - scale clinical studies should be conducted to quantify deep 
 lumbar stabilizing muscle responses in nmes training .
second , rusi is a powerful anatomic 
 imaging tool that can demonstrate gross architecture , but the power generated by both the 
 abdominal wall and lumbar region stimulation might be greater than the maximal voluntary 
 contraction ( mvc ) detectable by rusi .
studies using fine wire emg may provide a more 
 detailed view of the contributions of each stimulation protocol .
clinical studies , such as , 
 gait analysis , are required to assess dynamic sagittal imbalance improvements before , during 
 and after nmes of deep lumbar stabilizing muscles of patients with ldk . in conclusion ,
protocol a+b maximally stimulated all the studied deep spinal stabilizing muscles 
 ( lm , tra and oi ) as evidenced by rusi . the protocol a+b may aid the development of practical 
 nmes systems for ldk patients who suffer from postural deformity and lbp .
 [ purpose ] to investigate the effectiveness of three different neuromuscular electrical 
 stimulation ( nmes ) protocols for the deep lumbar stabilizing muscles of patients with 
 lumbar degenerative kyphosis ( ldk ) . 
 [ subjects and methods ] twenty patients with ldk were 
 recruited . 
 three stimulation protocols were investigated : stimulation of the abdominal 
 muscles ( protocol a ) ; stimulation of the lumbar muscles ( protocol b ) ; and simultaneous 
 stimulation of the abdominal and lumbar muscles ( protocol a+b ) . 
 images of the obliquus 
 externus ( oe ) , obliquus internus ( oi ) , transversus abdominis ( tra ) , and lumbar multifidus 
 ( lm ) muscles were captured by real - time ultrasound imaging ( rusi ) . 
 [ results ] the thickness 
 of lm was significantly greater during stimulation than at rest for all three protocols . 
 
 thicknesses of the abdominal muscles ( tra , oi , and oe ) were significantly greater during 
 stimulation than at rest for protocols a and a+b . 
 thickness increases in lm were 
 significantly greater during protocols b and a+b , but not during protocol a. thickness 
 increases in the abdominal muscles ( tra , oi , and oe ) were significantly greater during 
 protocols a and a+b , but not during protocol b. [ conclusion ] nmes can significantly 
 activate the deep lumbar stabilizing muscles of patients with ldk . 
 protocol a+b of nmes is 
 recommended to aid postural correction and low back pain ( lbp ) in patients with ldk . 