the lungs can not contract by themselves during respiration . instead , they passively 
 contract and relax as a result of the contraction and relaxation of the thoracic cage 
 respiratory muscles , leading to gas exchange between the air and the lungs1 .
while relaxed expiration is performed by 
 the passive recoil of the diaphragm , during forced expiration , the air is driven out as the 
 diaphragm is forced upwards by a rise in intra - abdominal pressure induced by contraction of 
 the abdominal muscles2 .
moreover , the 
 diaphragm , a component of core stability , plays a role in respiration and trunk stability by 
 controlling intra - abdominal pressure and reducing the stress on the spine through 
 cooperative action with the abdominal and pelvic floor muscles3 , 4 . the diaphragm is composed 
 of the muscles and tendons that separate the chest from the abdominal cavity , and forms the 
 floor of the thoracic cavity . beginning from the thoracic outlet , it is divided into three 
 parts  sternal , costal , and lumbar .
the costal part of the diaphragm connects with the origin 
 of the transversus abdominis in the shape of a finger on the insides of the costal 
 cartilages on both sides of the last six ribs5 .
the transversus abdominis is the diaphragm s partner , and its upper 
 part is connected to the inner part of the lower thoracic cage .
moreover , its back is linked 
 to the lumbar vertebra by discs comprised of fibers , while its lower part is joined to the 
 iliac crest and the inguinal ligament in the arched femoral region6 .
it has been reported that during lumbo - pelvic motion 
 control tests , diaphragmatic activity increases in healthy subjects7 and decreases in patients with diaphragmatic injuries8 .
moreover , patients with chronic lower back 
 pain have often been reported to have defects in posture and motor control9 , 10 . 

considering the anatomical structure of the diaphragm and the transversus abdominis , we 
 consider that decreased contractility of the diaphragm , which may be caused by diaphragmatic 
 injuries , would lead to a decrease in transversus abdominis activity and lumbar 
 stability .
this study aimed to determine the effects of enhanced diaphragmatic function achieved 
 through deep abdominal muscle strengthening exercises on respiratory function and lumbar 
 stability .
for this study , 22 subjects whose thoraxes opened no more than 5  cm during inspiration and 
 expiration and whose forced expiratory flow rates were around 300 m / l were recruited from 
 among 120 male and female students .
the subjects were randomly divided into an experimental 
 group of eleven ( five males and six females ) , who engaged in deep abdominal muscle 
 strengthening exercises , and a control group of eleven ( four males and seven females ) , who 
 experienced no particular intervention . those with muscular , skeletal , or nervous problems , 
 patients with lung diseases or lower back pain , and smokers were excluded .
the selected 
 subjects were provided with detailed explanation about the intent and content of this study 
 and signed a voluntary consent form .
the mean age , height , and weight of the subjects were 
 22.555.75 years , 166.278.65 cm , and 62.6413.60 kg , respectively , for the experimental 
 group , and 20.821.78 years , 159.184.7 cm , and 52.183.97 kg , respectively , for the control 
 group .
the gender of the subjects was analyzed using a  test , while the age , 
 height , and weight were analyzed using the independent t - tests .
there were no statistically 
 significant differences detected in the two analyses ( p>0.05 ) , which indicates the two 
 groups were homogneous .
the deep abdominal strengthening training method suggested by richardson et al.11 was modified and performed by the 
 experimental group .
the thoracic and abdominal motion during respiration in the hook - lying 
 position was observed while the subjects engaged in natural breathing , namely deep 
 breathing . by touching the ribs on both sides with the hands , increases in the transverse 
 diameter and the diameter of the thoracic cavity and its frontal opening during inspiration 

the subjects were instructed to hold their breath for ten seconds at the end of 
 inspiration .
ten repetitions of this breathing comprised one set of respiratory training , 
 and a total of five sets were performed by the subjects .
a one - minute break was given after 
 each set , and the training was conducted once a day three times a week , for four weeks .
a 
 cardio touch 3000s ( bionet ) was used to measure two pulmonary function indices , fvc ( forced 
 vital capacity ) and fev1 ( forced expiratory volume for 1 second ) , of the subjects .
the 
 measured values were recorded only when both measurements were obtained without any error . 

moreover , three values were recorded , and the average value was used in the analyses .
lumbar 
 stability was measured based on the contractility of the transversus abdominis by using a 
 pbu ( pressure biofeedback unit ) . for this measurement ,
the subjects were instructed to 
 practice their normal breathing patterns in the hook - lying position . while doing this , the 
 hollowing training method was performed using the transversus abdominis .
then , the subjects 
 were directed to maintain spinal stabilization in the neutral position , and the pbu was 
 placed on the lower back at the level of psis . with a basic pressure of 40 mmhg , the changes 
 were measured while the transversus abdominis was contracted during normal inspiration and 
 expiration . during the measurement , a physical therapist with more than ten years of clinical 
 experience palpated the point 5  cm inside the anterior superior iliac spine of the subjects 
 to evaluate the contraction of the transversus abdominis , thereby controlling the 
 compensation caused by the contraction of the rectus abdominal muscles and the external 
 oblique abdominal muscles , and inducing that of the transversus abdominis as far as 
 possible . increased pressure during the test indicateed improvement in the contractility of 
 the transversus abdominis , suggesting enhanced stabilization .
differences in the measured data were tested with the paired t - tests were conducted using 
 spss 12.0 for windows in order to compare the differences within each group before and after 
 the intervention .
the differences between the two groups were tested using the independent 
 t - test .
* p<0.05 ; fvc , forced vital capacity ; fev1 , forced expiratory volume in 1 second ; 
 pbu , pressure biofeedback unit in the comparison of fvc and fev1 before and after the training , the experimental group 
 showed significant increases in both fvc and fev1 .
furthermore , the comparison of the 
 contractility of the transversus abdominis before and after the training revealed that the 
 experimental group displayed significant changes in the contractility of the transversus 
 abdominis ( table 1 ) .
the independent t - tests was 
 carried out to examine differences in fvc , fev1 , and the contractility of the transversus 
 abdominis in the two groups before and after the training and the before - and - after changes . 

the results showed that the values before the training were not statistically significant , 
 while the experimental group exhibited significant before - and - after changes ( table 2 ) .
the diaphragm , the main muscle of inspiration , is involved in trunk stability and posture 
 control12 , and the transversus 
 abdominis engages in posture and motor control and respiration13 . among studies on respiratory muscle training ,
hall et 
 al.14 suggested a respiratory muscle 
 training method , while richardson et al.11 examined a deep abdominal muscle training method , and roussel et 
 al.15 looked into the changes in 
 breathing patterns experienced by chronic lower back pain patients .
lumbar instability is a major cause of lower back pain9 , and spinal stability is crucial for the prevention of lumbar 
 injuries16 .
akuthota and nadler17 described the core muscles that stabilize 
 the trunk and the spine regardless of the movements of the extremities as being the 
 diaphragm , the multifidus muscle , the transverse muscle of abdomen , and the pelvic floor 
 muscle , and also stated that these muscles act as one unit at the center of functional 
 kinetic chains .
in other words , spinal stability is achieved by the co - contraction of the 
 trunk muscles , and such contraction is necessary in order to maintain a proper level of 
 spinal stability to prevent and treat lower back pain18 .
michael et al.19 noted that the co - contraction of the abdominal muscles and the 
 diaphragm increases intra - abdominal pressure , fixes the trunk , and reduces the stress on the 
 spine , especially the lumbar region .
it automatically happens when a subject lifts a heavy 
 object , decreasing the load by about 50% in the high lumbar region , and about 30% in the low 
 lumbar region
. it also reduces the load experienced by the back muscles by more than 50% . 

these results suggest that well - built abdominal muscles may be important for the prevention 
 and treatment of spinal diseases .
the results of the present study indicate that the deep abdominal muscle strengthening 
 exercise was effective at increasing vital capacity .
the contractility of the diaphragm and 
 the transversus abdominis in particular influences the partial stabilization of the lumbar 
 spine and functions as a type of regulatory mechanism , causing changes in breathing 
 patterns .
to conclude , enhanced diaphragmatic function achieved via deep abdominal muscle 
 strengthening exercises not only increased respiratory volume but also played a role in 
 stabilizing the lumbar spine through the co - contraction of the transversus abdominis .
thus , 
 this method can be reduce lower back pain and enhance respiration and trunk stability when 
 lumbar stabilization exercises are clinically administered for patients with a low level of 
 stability .
furthermore , this method needs to be compared with other methods in future 
 studies .
   [ purpose ] the purpose of this study was to examine the effects of deep abdominal muscle 
 strengthening exercises on respiratory function and lumbar stability . [ subjects ] from 
 among 120 male and female students , 22 whose thoraxes opened no more than 5 cm during 
 inspiration and expiration and whose forced expiratory flow rates were around 300 m 
 / l were 
 recruited . 
 the subjects were randomly divided into an experimental group of eleven , who 
 performed deep abdominal muscle strengthening exercises , and a control group of eleven , 
 who received no particular intervention . [ methods ] 
 the subjects were instructed to perform 
 normal breathing in the hook - lying position . 
 they were then directed to hold their breath 
 for ten seconds at the end of inspiration . 
 ten repetitions of this breathing comprised a 
 set of respiratory training , and a total of five sets were performed by the subjects . 
 
 [ results ] deep abdominal muscle training was effective at enhancing respiratory function 
 and lumbar stabilization . [ conclusion ] the clinical application of deep abdominal muscle 
 strengthening exercises along with lumbar stabilization exercises should be effective for 
 lower back pain patients in need of lumbar stabilization . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION