individuals with back and hip pathologies are often taught to perform the bridging exercise 
 ( be ) in the hook - lying position , elevating the pelvis off the floor .
this exercise is 
 particularly useful for facilitating pelvic motions and strengthening the low back and hip 
 extensors , and it enhances motor control of the lumbo - pelvic region1 . to prevent lumbo - pelvic instability and low back pain ( lbp ) , healthy individuals
should 
 also do the bridging exercise , especially females , as they are quadriceps femoris dominant ; 
 i.e. , the quadriceps femoris is the first muscle to activate in response to injury 
 perturbations2 .
a dominant quadriceps 
 femoris causes poor endurance and delayed firing of the gluteus maximus muscle in subjects 
 with lower extremity instability and lbp3 , 4 . to increase the abdominal and hip extensor muscle activities ,
many clinicians have 
 emphasized using unstable devices , such as a swiss ball , ball cushion , or bosu ball , and 
 applying unilateral conditions5,6,7,8 .
however , studies have reported inconsistent results regarding the 
 activation patterns of the abdominal and hip extensor muscles during be .
baratta et al.9 showed that 
 antagonists regulate stabilization in response to distraction forces generated by the 
 agonist muscles .
the abdominal muscles attach to the thoracic cage proximally , and act 
 synergistically with the posterior paravertebral muscles to stabilize the symphysis10 .
the hip adductor muscles stabilize the 
 symphysis by bringing the lower extremity closer to the pelvis , and are antagonists of the 
 abdominal muscles .
moreover , hip adductor contraction synergistically facilitates 
 contraction of the pelvic floor and abdominal muscles , reinforcing the trunk muscles and 
 contributing to spinal stability11,12,13 . 

however , these theories have not been tested experimentally , especially the effects of 
 functional exercises such as bridging exercise with hip adduction ( beha ) on the abdominal 
 and hip extensor muscles .
therefore , we investigated the effects of the beha on the emg 
 activities of the abdominal and hip extensor muscles in females .
we hypothesized that beha 
 generates increased abdominal and hip extensor muscle emg activities compared to be .
health was defined as no history of any type of injury in the previous 6 months . 

their mean age was 29.5 ( range 
 2535 ) years , their mean height was 160.21 ( range 154169.5 ) cm , their mean weight was 53.11 
 ( range 4363 )  kg , and their mean body mass index ( bmi ) was 20.68 ( range 
 17.2223.61 )  kg / cm .
all of the protocols used in this study were approved by 
 the university of inje . before participation
, the procedures , risks , and benefits were 
 explained to all the participants , who gave their informed consent .
the participants ' rights 
 were protected according to the guidelines of the university of inje .
surface emg data were collected using a trigno wireless emg system with trigno emg sensor 
 ( delsys , boston , ma , usa ) surface electrodes .
the signal was full - wave rectified and the 
 root mean square value was calculated over 100 millisecond intervals . throughout the tests , 

the emg data were filtered using 
 standard band - pass filtering techniques with cutoffs of 20 and 450  hz . the emg data of each 
 muscle were converted from analog to digital using the program emg works acquisition and 
 analysis ( delsys ) .
the surface electrodes were placed over four muscle groups in a bipolar configuration on 
 the right side of the body : the 1 ) the rectus abdominis ( ra ) , centered on the muscle belly 
 midway between the pubis and the umbilicus ; 2 ) the external obliques ( eo ) , 5  cm above the 
 anterior superior iliac spine ; 3 ) the internal obliques ( io ) , 2  cm medial to the anterior 
 superior iliac spine ; and 4 ) the gluteus maximus ( gm ) , 33% of the distance between the 
 second sacral vertebra and greater trochanter at the midpoint of the muscle bellies . before 
 testing , the selected electrode locations were secured before conducting two manual muscle 
 tests ( mmts ) for each muscle , and the protocols were explained to ensure the participants 
 full understanding .
the mmts were used to identify the approximate maximum voluntary 
 isometric contraction ( mvic ) of each muscle and were performed following the techniques 
 described by kendall et al14 .
all mmts 
 consisted of a 5-s isometric contraction of each muscle , and the mvic data of the first and 
 last second of each contraction were discarded .
a single - group repeated measures design was used to collect muscle activation data for the 
 right ra , eo , io , and gm muscles .
a minimum 
 2-min rest between each contraction was enforced to minimize the effects of muscle fatigue . 

the hip joint was maintained in 
 neutral rotation using the procedure recommended by hlmich et al15 .
for the 45 hip flexion position , the knee joint was 
 maintained in 60 of flexion with the feet on the floor , toes pointed forward , and hands on 
 the floor by the subjects ' sides , palms down .
the subjects lifted their pelvis until 0 of 
 hip flexion was reached with the pelvis in neutral alignment .
the position was held for 5 
 s. participants performed the beha using a pressure bio - feedback unit ( stabilizer , usa ) to 
 control the force of hip adduction .
the 
 participant was instructed to perform hip adduction to maintain a pressure of 60 mmhg .
then , 
 with the hip joint in full extension and a neutral position , the emg was recorded for 5 
 s. data of each muscle were normalized as percentages of mvic .
statistical analysis was 
 performed using spss ver . 18.0 for windows ( spss , chicago , il ) .
the paired 
 t - test was used to evaluate differences in emg activities between be and 
 beha .
ra : rectus abdominis ; eo : external obliques ; io : internal obliques ; gm : gluteus 
 maximus ; be : bridging exercise ; beha : bridging exercise with hip adduction the activation of each abdominal and hip extensor muscle during be and beha is summarized 
 in table 1 . for the beha ,
the emg signal 
 amplitude ( mean  sd ) increased significantly in ra ( 10.43  9.9% vs. 5.59 
  3.59% mvic ) , eo ( 22.11  13.4% vs. 11.3 
5.06% mvic ) , io ( 26.97  18.41% 
 vs. 7.82  17.63% mvic ) , and gm ( 26.88  11.04% vs. 20.4 
  8.9% mvic ) .
the exercises 
 investigated are thought to be of help in stabilizing the lumbar spine region .
when 
 prescribing exercise therapy , it is important to understand the muscle activities of healthy 
 individuals .
the results show that performing hip adduction increased the emg activities of ra , eo , io , 
 and gm muscles during the bridging exercise .
a possible explanation for the greater muscle 
 activity during performance of beha is that the hip adductors originate proximal to the 
 inferior aspect of the body and ischium and insert distally on the femur , affecting the 
 control of the trunk muscles attached to the pelvis .
they are linked to the trunk muscles to 
 support the trunk or fix the trunk muscles and play a role in promoting contraction of the 
 internal abdominal muscles11 , 16 .
hip adductor contraction appears to contribute to the 
 increased abdominal muscle activity observed during the bridging exercise .
the gluteus maximus plays a major role in stabilizing the pelvis during upright activities 
 and might theoretically influence the development of lbp17 , 18 .
however , our results show that the emg activity of the gm muscle increased 
 during beha .
although the hip adductors are located on the inner thigh , the posterior fibers 
 of the adductor magnus activated the powerful hip extensors20 .
first , our results can not be generalized to other 
 populations , as all subjects were healthy young females .
future studies should evaluate the effects of different 
 pressures on trunk and leg muscle activities .
our results suggest that bridging exercise with hip adduction strengthens ra , eo , io , and 
 gm and could be used clinically to prevent lbp .
   [ purpose ] this study compared the activities of the abdominal and hip extensor muscles 
 between the bridging exercise ( be ) and bridging exercise with hip adduction ( beha ) 
 positions in women using electromyography ( emg ) . [ subjects ] we recruited 14 healthy adult 
 females with no history of low back pain . 
 [ methods ] the subjects performed bridging 
 exercises with and without hip adduction . 
 the emg activities of the rectus abdominis ( ra ) , 
 external oblique ( eo ) , internal oblique ( io ) , and gluteus maximus ( gm ) muscles were 
 recorded . 
 [ result ] the emg activities of all muscles were significantly increased during 
 the beha compared to the be . 
 [ conclusion ] the bridging exercise with hip adduction 
 produced greater activation of the abdominal and hip extensor muscles . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION