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Paper text:
ever since humans began to walk upright , some of their muscles have always been activated 
 to maintain the balance of the body on narrow support surfaces .
if these posture - maintaining 
 muscles lose their function , low back pain will be induced due to the maintenance of 
 unstable postures1 . compared to healthy 
 persons ,
patients with low back pain have reduced proprioceptive sense in the deep lumbar 
 muscles , which makes the spine unstable , and this may lead to the recurrence of low back 
 pain2 .
when healthy persons without any 
 low back pain move their upper or lower limbs quickly , their transversus abdominis ( tra ) 
 muscles contract first to contribute to lumbar stabilization .
however , in the case of 
 patients with low back pain , the tra muscles do not contract first3 . delayed contraction of the tra makes the trunk unstable , 
 leading to reduced motor and postural control abilities and inefficient actions of the 
 spinal muscles4 .
richardson et al.5 reported that the low back pain recurrence 
 rate was reduced from 75 to 35% for three years after 
abdominal drawing - in  exercises were 
 performed to strengthen the tra and multifidus muscles .
page6 advised that rather than exercises using stable bearing surfaces , 
 lumbar stabilization exercises using an unstable support surface are more effective for the 
 maintenance of postural balance and the recovery of proprioceptive senses .
kang et al.7 reported that according to the measurements 
 taken using ultrasonography and the visual analogue scale after patients who had received 
 herniated disc surgery had performed lumbar stabilization exercises using slings , which are 
 unstable support surface , the activity of the tra muscle increased and pain was relieved . 
 therefore , these previous studies indicate that closed chain exercises on an unstable 
 support surface have the effect of activating lumbar stabilization muscles . the local 
 vibration used for the intervention in this study took the form of isometric exercises that 
 have been attracting great attention after results indicating that they positively affect 
 motor function improvement and increase energy metabolism and blood flow rates8 .
in addition , rittweger et al.9 reported that when vibration and exercises 
 were performed by a group of low back pain patients , there was evidence of pain relief and 
 improvement in their neuromuscular control ability .
this study compared and analyzed the changes in the thickness and length of the tra muscle 
 when vibration was applied to low back pain patients while they performed closed chain 
 exercises on an unstable support surface .
the study subjects were 64 healthy university students residing in daegu , korea , who were 
 randomly divided into a bridge exercise with sling and vibration group ( besvg ) of 30 
 students , and a bridge exercise with sling group ( besvg ) of 34 students .
the besvg s mean 
 age was 21.81.6  years , their mean height was 166.17.7  cm , and their mean weight was 
 61.211.2  kg .
the besg s mean age was 22.51.8  years , their mean height was 169.67.2  cm , 
 and their mean weight was 60.79.4  cm . those who had neurologic or orthopedic problems or 
 could not perform supine / prone bridge exercises due to pain or other problems were excluded 
 from the study .
all of the participants understood the purpose of this study and provided 
 their written informed consent prior to their participation in this study , in accordance 
 with the ethical principles of the declaration of helsinki .
when the subjects in the besvg performed the bridge exercise in supine positions , each 
 adopted a supine position on the table .
for the starting posture , the subjects placed their 
 two hands on the floor to support the body , maintained 90 flexion postures of the hip and 
 knee joints , and placed both ankles in a narrow sling . during the exercise , the subjects 
 loaded their weight on both lower limbs , avoiding pelvic tilt and lifted their hip so that 
 the trunk , pelvis , and lower limbs made a straight line .
when the subjects in the besvg 
 performed the bridge exercise in the prone position , each adopted a prone position on the 
 table .
for the starting posture , the subjects placed their two ankles in a narrow sling 
 while maintaining the shoulder and elbow joints at 90. during the exercise , the subject 
 loaded their weight on both lower limbs and elbows , avoiding pelvic tilt and lifted their 
 hips so that the trunk , pelvis , and lower limbs made a straight line .
the performance of 
 each exercise four times constituted one set , and nine sets of the bridge exercise were 
 performed in both the supine and prone positions .
the besg performed the same bridge exercises without local 
 vibration in the supine and prone positions .
local vibration was applied by suspending the two ropes of the sling that supported both 
 lower limbs from vibration equipment ( redcord stimula , norway ) , so that 
 vibration was applied only while the subjects were performing bridge exercises and not 
 during rest times .
vibration was applied at 15  hz in the first 3 sets , at 20  hz in the next 
 3 sets , and at 30  hz in the last 3 sets .
an hd11xe ultrasound system ( philips , netherlands ) was used for ultrasonic imaging , and 
 measurements were conducted by one person who was skilled in ultrasonic measurement . before 
 the ultrasonic measurements were taken , subjects lay comfortably in the supine position . a 
 pressure biofeedback unit ( pbu ) was placed between the umbilicus and the floor , and a 
 triangular pillow was placed under the subject s knees for support , thereby relaxing the 
 subject s lower limbs . an assistant adjusted the pressure of the pbu to 40 mmhg , and the 
 tester then placed the probe transversely on the top of the iliac crest and moved it to the 
 center of the abdomen to align the end point of the tra muscle with the end point of the 
 screen .
once this had been done , the subject  drew in  the abdomen within the range in which 
 the gradation of the pbu did not change , and the distance moved by the end point of the tra 
 muscle was measured . in this way
, the distance was measured three times , both before and 
 after the intervention and the average values were recorded . since the total length of the 
 tra muscle could not be measured due to the nature of ultrasonography , the sliding distance 
 from the abdomen to the outside was measured instead . for the statistical analyses , intra - group changes in tra thicknesses and lengths
were 
 analyzed using the paired t - test , and intergroup comparisons were performed using the 
 independent sample t - test .
statistical processing was conducted using spss 12.0ko ( spss , 
 chicago , il , usa ) with a significance level of =0.05 .
according to the results of this study , in the intragroup comparison , the besvg showed a 
 significant increase in tra thickness and a significant decrease in tra length ( p<0.05 ) . 

the besg showed a significant increase in tra thickness ( p<0.05 ) . in the intergroup 
 comparison ,
the besvg showed a significant increase in tra thickness and a significant 
 decrease in tra length compared to the besg ( p<0.05 ) ( table 1table 1.intergroup comparison of tra thickness and lengthtragroupprepostthickness ( cm)besvg**0.30.10.50.1besg**0.30.10.40.1length ( cm)besvg*0.90.20.80.2besg1.00.20.90.3besvg : bridge exercise with sling and vibration group , besg : bridge exercise with 
 sling group , * : paired t - test , : independent sample t - test , 
 : p<0.05 , * * : p<0.01 ) .
besvg : bridge exercise with sling and vibration group , besg : bridge exercise with 
 sling group , * : paired t - test , : independent sample t - test , 
 : p<0.05 , * * : p<0.01
bridge exercises for lumbar stabilization use the performer s weight , increase joint 
 alignment and stability , and improve proprioceptive stimuli and dynamic stabilization10 . in a study involving 51 patients with 
 chronic low back pain ,
saliba et al.11 
 demonstrated that bridge exercises on an unstable support surface provided by slings were 
 more effective at increasing tra muscle activity than bridge exercises on stable bearing 
 surfaces as measured by ultrasonography .
eom et al.12 reported that bridging exercises performed by healthy persons using 
 slings as an unstable support surface showed larger increases in tra thicknesses than 
 bridging exercises performed by the same persons on stable bearing surfaces . in a study 
 conducted by brumagne et al.13 with 
 chronic low back pain patients , in which proprioceptive sense exercises and local vibrations 
 were additionally applied , proprioceptive stimuli and deep muscle control abilities of the 
 subjects improved .
the studies cited above indicate that closed chain exercises on an 
 unstable support surface are effective lumbar stabilization exercises for activating the tra 
 muscle .
hides et al.14 reported that 
 according to mri and ultrasonography conducted after athletes had performed drawing - in 
 exercises , the tra muscle became thicker and shorter .
hides et al.15 reported that weight - bearing stabilization exercises 
 performed by low back pain patients greatly increased the thickness of the internal oblique 
 muscles , and shortened the tra muscle . according to the results of this study , in the intragroup comparisons the besvg showed a 
 significant increase in tra thickness and a significant decrease in tra lengths ; and the 
 besg showed a significant increase in tra thicknesses . in the intergroup comparison ,
the 
 besvg showed a significant increase in tra thickness and a significant decrease in tra 
 lengths compared to the besg .
given these results , we consider the local vibration applied 
 to the besvg during closed chain exercises on an unstable support surface improved tra 
 muscle strength and power and lumber / pelvic tilt repositioning senses , thereby affecting tra 
 thickness and length more than in the besg .
fontana et al.16 reported that when healthy persons performed weight - bearing 
 exercise while vibration was applied , the subjects lumber / pelvic tilt repositioning senses 
 were improved by as much as 39%
. therefore , applying local vibration during bridge exercises 
 using slings in clinics should be an effective method for lumbar stabilization , because it 
 improves tra muscle activation .
in addition , it can be presented to patients with chronic 
 low back pain as an exercise intervention method in clinics .
although many previous studies have measured tra muscle activity through the thickness of 
 the muscle using ultrasonic imaging , those that used local vibrations are few in number . 

therefore , it is important that related studies in this field are undertaken in the 
 future .
[ purpose ] this study examined the effects of closed chain exercises performed with local 
 vibration applied to an unstable support surface on the thickness and length of the 
 transverse abdominis . [ subjects ] the subjects were 64 healthy university students who were 
 randomly assigned to a bridge exercise with sling and vibration group ( besvg , n=30 ) and a 
 bridge exercise with sling group ( besg , n=34 ) . 
 [ methods ] the bridge exercise was repeated 
 four times per set and a total of 18 sets were performed : 9 sets in a supine position and 
 9 sets in a prone position . in both the besvg and the besg groups , the thickness and 
 length of the transverse abdominis ( tra ) were measured using ultrasonography with the 
 abdomen  drawn - in  and the pressure of a biofeedback unit maintained at 40 mmhg , both 
 before and after the intervention . [ results ] in intra - group comparisons , the besvg showed 
 significant increases in the thickness of the tra and significant decreases in the length 
 of the tra . 
 the besg showed significant increases in the thickness of the tra . 
 the besvg 
 showed significant increases in the thickness of the tra and significant decreases in the 
 length of the tra compared to besg . 
 [ conclusion ] closed chain exercises for the lumbar 
 region performed with local vibration applied to slings , which are unstable support 
 surfaces , are an effective intervention for altering the thickness and length of the 
 tra .