patients with chronic low back pain ( clbp ) have weaker and unbalanced lumbar deep muscles 
 compared to people without low back pain . moreover , their proprioception is decreased , which 
 eventually causes problems in spinal stability which result in recurring low back pain1 . pakhurst and burnett2 argued that diminished proprioception is highly correlated 
 with the occurrence of low back pain . luoto et al.3 also reported that patients with lower back pain had less lumbar 
 sense and motion control ability than those without low back pain . lumbar instability 
 induces pain , decreases endurance and flexibility , and limits the range of motion of the low 
 back4 , distorting the normal signals 
 coming from the muscles and sensory organs and impairing balance5 . it is a neural 
 signal that begins in the nerve terminals known as mechanoreceptors , and travels to the 
 central nervous system6 . proprioception is 
 an important biofeedback for controlling nerve roots , balance , and mobility as well as 
 securing and maintaining joint stability6 , 7 . information from proprioceptive senses 
 plays an important role in movement and balance as well as control of the neural muscles , as 
 it transfers information regarding body movement and the position of the joints to the 
 central nervous system8 . when 
 proprioception is impaired , the amount of movement , sensory information about the position 
 of the joint where the movement takes place , and the amount and properties regarding muscle 
 contraction , etc . are changed . as a result , the ability to respond to unexpected and 
 destabilizing forces is diminished , potentially causing injury9 . proprioceptive malfunction in patients with low back pain causes 
 chronic pain and a limited range of joint motion5 . hence , accurate stimulus input of proprioception is important for 
 normal movement and articular damage prevention . one method of evaluating kinesthesia involves measuring the cognition 
 threshold of slow passive movement . meanwhile , joint position sense can be evaluated by 
 error determination of the active or passive reproduction of joint angles10 , 11 . in the case of the loss of joint position sense , movement ability 
 diminishes and carrying out daily activities moreover , it hampers 
 learning ability when acquiring new movements , potentially causing degeneration12 . this study chose to use bridge exercises as a means of reinforcing weakened body trunk 
 muscles among patients with clbp . the bridge exercises used a comfortable posture that 
 reduced the pain of the patients with low back pain . they are widely used in clinics , as 
 they stabilize the trunk and enhance the muscle strength of the buttocks and lower 
 limbs13 . most previous studies of 
 bridge exercises have focused on the muscle activity of the trunk and lower limbs14 , 15 ; however , research on proprioception is scarce . this study implemented bridge exercise programs for eight weeks and investigated their 
 effect on the oswestry disability index score and proprioception of the trunk by measuring 
 the activity index and joint position sense , respectively , using a sample of patients with 
 low back pain with the purpose of suggesting an effective method of using bridge 
 exercises . a total of 38 patients with clbp undergoing physical therapy at hospital p were selected . they were randomly allocated to the following three groups according to bridge exercise 
 type : the supine bridge exercise ( sbe ) group , the supine bridge on swiss ball exercise 
 ( sbse ) group , and the prone bridge exercise ( pbe ) group . of the 38 participants , 13 ( 34.2% ) 
 were male and 25 ( 65.8% ) were female . the average age , weight , and height of the sbe group 
 was 39.4  years , 60.9  kg , and 163.5  cm , respectively ; the average age , weight , and height of 
 the sbse group was 41.9  years , 59.5  kg , and 163.7  cm , respectively ; and the average age , 
 weight , and height of the pbe group was 42.6  years , 63.9  kg , and 165.1  cm , respectively . before the test , the researchers explained the purpose and methods of the research to all 
 of the subjects ; then , they were asked to complete the odi . the research participants also 
 signed written informed consent forms in accordance with the declaration of helsinki before 
 beginning the experiment . the protocol for this study was approved by the local ethics 
 committee of the catholic university of daegu . the patients were ages between 20 and 
 50  years old and had suffered from clbp for a period of over six months . they had been 
 diagnosed as having chronic low back pain via x - rays , ct scans , mris , etc . those with 
 problems in their vestibular organs or neural damage , those taking balance - related 
 medicines , those with a history of spinal surgery due to orthopedic problems , and those who 
 were unable to perform the exercise program were excluded from the sample . exercise 1 ( supine 
 bridge exercise ) : lying down , the arms are spread at approximately 30 and the knees are 
 flexed at 90 ; the palms are placed face down on the ground , and the head and neck are kept 
 straight with the eyes looking at the ceiling . exercise 2 ( supine bridge on swiss ball 
 exercise ) : with an identical starting position to exercise 1 , the feet are placed on a swiss 
 ball . exercise 3 ( prone bridge exercise ; the plank ) : in the prone position , the body weight 
 is supported on the forearms and the toes , with the elbows flexed at 90 , the neck slightly 
 extended , and the eyes looking forward . for each group , one set of each exercise consisted of 30 seconds of exercise followed by 30 
 seconds of rest repeated five times . each group performed three sets per day three times per 
 week . in order to minimize error , an experienced physical therapist instructed and observed 
 the subjects in a designated area to ensure that they correctly performed the exercises . a zebris ( zebris medical gmbh cms100 , germany ) was used to evaluate proprioception . zebris 
 is a device that measures the range of motion of the spine and has been proven to have high 
 stability and reliability16 . two sensors 
 are used to measure the joint angle of the spine using ultrasound . the patients first stood in a neutral position , 
 and the measurements were made in flexion , extension , right rotation , and right lateral 
 flexion in the standing position . the patients received instruction while they were in the 
 neutral position to keep their eyes open so that they could recognize the angle . then , they 
 were told to reproduce an arbitrary angle with their eyes closed . the patients were not allowed 
 to receive visual feedback from the monitor . to prevent learning effects , the difference between the actual angle and the arbitrary 
 angle was measured three times , and the average value was used . the paired t - test was 
 conducted to examine differences in proprioception and the odi before and after the exercise 
 program . analysis of covariance ( ancova ) was performed by controlling the pre - test 
 proprioception as a covariance . the bonferroni test was conducted to examine post - test 
 differences according to the exercise method . in the case of lumbar flexion and extension , joint position sense showed a statistically 
 significant difference after the exercise program in all three groups ( p<0.05 ) . in the 
 case of lumbar lateral flexion and lumbar rotation , joint position sense did not show a 
 statistically significant difference after the exercise program ( table 1table 1.comparison of joint position sense among groups ( unit : degree)caterorygroupprepostchangeexercise 14.991.273.221.101.771.27flexionexercise 24.571.692.591.051.971.55exercise 35.511.662.313.413.191.24exercise 12.960.671.950.721.010.80extensionexercise 22.450.831.780.700.670.67exercise 32.780.881.260.511.510.94exercise 13.702.182.101.221.601.73lateral flexionexercise 23.031.402.351.310.671.40exercise 33.331.182.171.141.161.50exercise 12.130.711.860.790.270.79rotationexercise 22.640.961.760.890.870.98exercise 32.190.861.380.580.800.91*p<0.05 , * * p<0.001 . the odi showed a statistically significant difference after the exercise 
 program in all three groups ( p<0.05 ) . according to the bonferroni post - test results after 
 controlling the pre - test value as a covariance in order to verify the between - group effect , 
 there was a difference in joint position sense in lumbar flexion between the sbe and pbe 
 groups ( p<0.05 ) . moreover , there was a difference in joint position sense in lumbar 
 extension and the odi between the sbe and pbe groups and between the sbse and pbe groups 
 ( p<0.05 ) ( table 2table 2.comparison of oswestry disability index among groups ( unit : score)categorygroupprepostchangeexercise 139.6514.527.586.812.0610.1odiexercise 238.3010.127.218.111.08 6.3exercise 344.4213.123.873.620.5513.1*p<0.05 , * * p<0.001 . however , there were no between - group effects of lumbar rotation and lateral 
 flexion . odi : oswestry disability index .   significantly 
 different compared with exercise 1 .   significantly different this study conducted eight weeks of bridge exercises to investigate their effects on odi 
 scores and proprioception of patients with chronic low back pain . hence , instability can be said to be the biggest factor inducing all kinds of lower back 
 pain17 . the subjects of this study were patients with clbp who had instability such as lumbar 
 spondylolisthesis , lumbar herniated intervertebral disc , lumbar spinal stenosis , sacroiliac 
 articulation syndrome , and lumbar sprain . due to individual variation or pathological 
 problems , patients with clbp have low lumbar 
 flexibility due to decreased mobility , and their muscle strength and muscle endurance are 
 often weaker than those of subjects without clbp . the subsequent decrease in lumbar function 
 is linked to pain and fatigue in the lumbar muscles ; hence , it is known that strengthening 
 the lumbar muscles is critical for ameliorating low back pain18 . in order to verify the effect on the proprioception of chronic low back pain sufferers , 
 this study measured the lumbar joint position error . according to our results , in the case 
 of lumbar flexion , joint position error decreased by 1.77 , 1.98 , and 3.2 in the sbe 
 group , the sbse group , and the pbe group , respectively , after the eight weeks of exercise . all three groups showed a significant difference after the exercise program , and a 
 significant difference was observed between the sbe and the pbe groups . in the case of 
 lumbar extension , the sbe group showed a decrease of 1.01 , the sbse group showed a decrease 
 of 0.67 , and the pbe group showed a decrease of 1.52. all three groups showed significant 
 differences after the exercise program , and a significant difference was observed between 
 the sbe and pbe groups and between the sbse and pbe groups . in the case of lumbar lateral 
 flexion and rotation , all three groups showed significant differences after the exercise 
 program , but no between - group differences were found . one remarkable finding was that the 
 bridge exercise type of the pbe group facilitated a more accurate joint repositioning sense 
 than the exercises of the sbse and sbe groups . to improve proprioception , the golgi tendon organ , located at the muscle spindle and 
 musculotendinous junction , needs to be stimulated to activate the receptors . janwantanakul 
 et al.19 reported that the accuracy of 
 joint position sense improved at the end point of the range of motion , when the resistance 
 tension of muscle , tendon , and ligament against movement increased . sensory function was enhanced by the interaction 
 between the muscles surrounding the shoulder joint and the body trunk muscle , since the 
 upper limbs supported body trunk . this is because the prone bridge exercise requires more 
 muscle activity as well as a higher level of balance and exercise control than a 
 conventional bridge exercise . moreover , the muscle activity is surmised to have increased 
 more since more muscles were mobilized in order to maintain the stability of the trunk . as 
 increase in muscle activity stimulates muscle spindles and joint receptors in the muscles , the accuracy of the sensory integration process is enhanced , enabling correct joint 
 repositioning . kong et al.14 reported 
 that muscle activity in the trunk increased more when performing the prone bridge exercise 
 ( performed by a group of normal people ) than other bridge exercises , and argued that the 
 muscle activity increased to overcome the instability . hence , for patients with clbp who have 
 spinal instability and potential degenerative diseases , an exercise method that enhances 
 proprioception impaired by decreased joint position sense should be considered . appropriate evaluation is required to select the best pain therapy method and determine its 
 therapeutic effects . the odi is an objective measurement tool that is used not only for 
 evaluating subjects after surgery , but also the effects of the treatment , as it reveals the 
 overall severity of impediments to daily living and physical activities . in the present 
 study , the odi scores significantly decreased after the eight - week exercise program in all 
 three groups . there was a difference between the sbe and pbe groups and between the sbse and 
 pbe groups ; the pbe group in particular showed a great deal of improvement . the results 
 indicate that for patients with chronic low back pain , the prone bridge exercise was the 
 most effective exercises at reducing low back pain and impediments to activity , in a 
 comparison with the conventional bridge exercise and bridge exercise on a swiss ball . this 
 is consistent with the results of marshall and murphy20 who reported a significant decrease in the odi after the swiss ball 
 exercise . it is also consistent with the results of hicks et al.21 who showed there were statistically significant decreases 
 in the visual analog scale and the lumbar disability index after an eight- week lumbar 
 stabilization exercise program . in conclusion , the prone bridge exercise more effectively enhanced joint reposition sense 
 impaired by diminished proprioception by securing the stability of the body trunk via 
 activating the trunk muscles than the conventional bridge exercise . the odi results suggest 
 that the prone bridge exercise is effective at enhancing quality of life as it reduces pain 
 and impediments to activity .
[ purpose ] the purpose of this study was to investigate the effect of bridge exercises on 
 the oswestry disability index ( odi ) scores and proprioception among patients with chronic 
 low back pain ( clbp ) . 
 [ subjects and methods ] a total of 38 patients participated in this 
 study . 
 after eight weeks of bridge exercise , the joint position angle of the body trunk 
 was measured and the odi was used in survey form to investigate the intensity of the 
 patients low back pain . [ results ] after eight weeks of exercise , the odi showed 
 significant differences in all three groups . 
 subjects joint position sense of the trunk 
 in both lumbar flexion and extension was also significantly different after completing the 
 exercise program ; this was true for all three groups . 
 [ conclusion ] performing the prone 
 bridge exercise for eight weeks improved proprioceptive function and reduced pain and 
 impediment of activity , showing it a more effective exercise than other bridge 
 exercises .