according to predictions by the world health organization , the number of smokers who will 
 die from cigarette - related diseases will surpass the number of people dying from aids , 
 traffic accidents , suicide , and murder combined by 20201 . due to the presence of various harmful substances in cigarettes , 
 smoking can cause many diseases . nicotine  which is one of the major constituents of 
 cigarettes causes arteriosclerosis , coronary artery disease , chronic obstructive pulmonary 
 disease ( copd ) , and other problems that result not only in low cardiopulmonary function2 but also in relatively diminished daily 
 living ability and endurance in smokers compared with that in non - smokers3 . moreover , it is common knowledge that 
 smoking is very highly correlated with occurrence of respiratory diseases . diaphragmatic 
 breathing is a good technique for respiration and relaxation of the lungs because it enables 
 sufficient exchange of oxygen and carbon dioxide . it is reported to be effective in ( 1 ) 
 improvement of ventilation efficiency , dyspnea , and activity ability4 ; reduction of metabolic acidosis ; alleviation of back 
 pain5 ; spine correction6 ; abdominal strengthening7 ; and improvement of body composition and 
 flexibility8 . in our current social 
 climate , the number of male smokers in their twenties is rapidly increasing and this trend 
 is becoming a social problem . our study attempts to verify the effects of diaphragm 
 respiration exercises on respiratory function in long - term male smokers in their 
 twenties . all research subjects were 40 male students between 20 and 29  years of age enrolled at 
 university p , located in gyeongbuk , korea . they were randomly and evenly divided ( 14 members 
 per group ) into a diaphragm respiration exercise group and a control group . we conducted 
 interviews with every subject and recorded individual measurements for each weight , body fat 
 percentage , smoking history , smoking amount , smoking habit , drinking habit , diet , disease 
 history , and family history . only subjects who were not receiving medical treatment for 
 respiratory diseases and who had a clean family medical history and personal habits were 
 selected . among smoking habits , those who smoked cigars other than filtered cigarettes or 
 tobacco pipes were excluded . only subjects who have been smoking for 1 to 3  years were 
 included . we ensured that the research subjects fully understood the research project and 
 signed consent was obtained from each participant . our study was approved by the committee 
 of clinical testing at korea nazarene university and was screened according to the ethical 
 standards of the helsinki declaration . general characteristics of study participants are 
 summarized in table 1table 1.general participant characteristicseg ( n = 14)cg ( n = 14)age ( years)23.1  1.322.8  0.4height ( cm)173.7  5.0175.2  3.9weight ( kg)64.5  4.261.7  5.7smoking period ( years)2.2  0.20.0  0.0values eg : experimental group ; cg : control group the experimental group performed 30-min diaphragm respiration exercises 3 times per week 
 for 4 weeks . the exercise involved subjects lying in the supine position with the researcher 
 placing his or her hand on the upper part of the subject s rectus abdominis , ( i.e. , 
 immediately below the frontal costal cartilage ) , and the subject breathing in deeply and 
 slowly out through the nose . simultaneously , the shoulder was maintained in relaxed position 
 and the upper chest was fixed so that only the abdomen was allowed to rise . afterward , using 
 controlled exhalation , the subject was told to slowly release all of the air outward9,10,11 . in the control group , each participant performed a cycling exercise using motomed 
 ( reck - technik gmbh & co , betzenweiler , germany ) , which allowed for regular and 
 repetitive training without affecting respiration . the strength of the training was 
 controlled so that the heart rate of the participants did not exceed 20% of the heart rate 
 reserve12 . if a subject complained of fatigue or dizziness during the respiration exercise , a break 
 was taken and exercise resumed some time later . prior to the experiment , the tester taught 
 each subject the proper method for the respiration exercise 2 or 3 times to ensure that the 
 subject was comfortable performing it . pulmonary function of the participants was measured in a sitting position using a tool 
 called fitmate ( cosmed , sri , italy ) . to ensure accurate measurements , the tester explained 
 and demonstrated the exercise to each subject beforehand . both the experimental and control 
 groups were instructed to use the mouthpiece and to block the nostrils during the 
 measurement so that air was neither inhaled nor exhaled through the nose . starting from 
 exhalation , subjects slowly exhaled to maximum level following the tester s signal and then 
 slowly inhaled ; tidal volume ( tv ) , inspiratory reserve volume ( irv ) , expiratory reserve 
 volume ( erv ) , inspiratory capacity ( ic ) , and volume capacity ( vc ) were measured at this 
 time13 . three measurements were made 
 for each pre - test and post - test value , and the average of the 3 values was used as the final 
 value . when comparing the breathing capacity of the experimental and control groups before and 
 after the experiment , the experimental group showed significant changes in tv , irv , ic , and 
 vc ( p < 0.05 ) , but no significant change in erv ( p > 0.05 ) . by contrast , the control 
 group showed no significant change in any parameter ( p > 0.05 ) . in testing the 
 differences between the experimental and control groups in their changes before and after 
 the experiment , vc showed a significant change ( p < 0.05 ) , while tv , irv , erv , and ic 
 showed no significant changes ( p > 0.05 ) ( table 
 2table 2.comparison of respiratory function between experimental and control 
 subjectsegcgpre - testpost - testpre - testpost - testtv ( l)0.5  0.10.6  0.0 * 0.5  0.00.5  0.0irv ( l)2.2  0.12.4  0.1 * 2.4  0.12.5  0.1erv ( l)1.5  0.01.8  0.01.6  0.01.6  0.0ic ( l)2.7  0.33.0  0.2 * 2.9  0.13.0  0.2vc ( l)4.2  0.24.8  0.2 * 4.5  0.64.6  0.1mean  se . * * significant difference from pre - test value , p < 0.05 . 
 significant difference in gains between the two groups , p < 0.05 . korea is currently experiencing a steady increase in smoking rate among males in their 
 teens and twenties . in all likelihood , this population is at a greater risk of developing 
 respiratory diseases in future . respiration training in addition to psychological and 
 medical treatments should be an active intervention in any anti - smoking program ; however , in 
 reality , the approach to professional respiration training is very limited and depends on 
 simple respiration exercises . hence , it is important to implement professional respiration 
 training as a means of recovering the decreased breathing ability of current smokers and of 
 lowering the smoking rate . the effectiveness of direct treatment by therapists specializing 
 in respiration training has already been proven14 , 
 15 . our study implemented diaphragm 
 respiration training that improved breathing ability , along with lung window setting of the 
 thoracic cage , by improving diaphragmatic function , which is the major factor that affects 
 the efficiency of breathing . we examined the impact of diaphragm respiration training on 
 pulmonary function of normal males in the age range of 20 to 29  years . in order to 
 ameliorate subject muscle fatigue and efficiently increase muscle strength , exercise 
 repetition number , sustained time , and resting time should be properly standardized16 . it is known that the experiment is most 
 effective when implemented for 4 to 12 weeks , 2 to 5 times per week , with each session 
 lasting no longer than 20 to 30  min . taking this fact into consideration , we opted for 
 30-min exercise sessions performed 5 times per week for 4 weeks . the 
 experimental group showed significant increases in tv , irv , ic , and vc after the experiment , 
 while there was no significant increase in erv . examining the changes in the experimental and control 
 groups after the experiment , the experimental group showed more increases than the control 
 group in every section ; however , only vc revealed a significant increase . it is hypothesized 
 that repetitive training of reinforcing the strength of the diaphragm muscle against 
 therapist resistance improved the subjects inspiratory muscle function . this subsequently 
 increased thoracic mobility , thereby resulting in improved breathing ability . in a study conducted by enright et al.17 , normal people who had undergone high frequency inspiratory muscle 
 training registered significant increases in breathing capacity , total breathing capacity , 
 inspiratory muscle strength , and inspiratory endurance . in a study conducted by 
 townsend18 , normal people who had 
 undergone respiration training exhibited large differences between the resultant inspiratory 
 volumes and expiratory volumes . jones et al.19 reported that under normal conditions , tv increased among copd 
 patients after diaphragmatic breathing exercises . moreover , pursed - lip breathing exercises 
 contributed to increased final ic and instant ventilation volume20 in these patients . decreased final expiratory capacity and 
 increased final ic previous studies that 
 examined the effect of respiration exercises on normal people like those in this study or on 
 copd patients showed results consistent with or similar to this study . we believe that data that are more objective can be obtained by comparing breathing between 
 different age groups through a study on smokers from different age groups , in addition to 
 those in their twenties . in addition , we consider it imperative to implement diverse 
 exercise programs aimed at improvement of breathing , especially among smokers .
[ purpose ] we investigated how diaphragm respiration exercises can affect pulmonary 
 function in long - term male smokers in their twenties . [ subjects and methods ] twenty - eight 
 healthy males between 20 and 29  years of age were randomly divided into an experimental 
 and a control group ( 14 members each ) . 
 the experiment was conducted during 30  min 
 sessions , 3 times a week for 4 weeks . 
 the experimental group performed diaphragm 
 respiration exercises and the control group performed exercises using motomed . 
 pulmonary 
 function ( tidal volume , breathing capacity , inspiratory reserve volume , inspiratory 
 capacity , and expiratory reserve volume ) was evaluated and analyzed before and after the 
 experiment . [ results ] 
 our results revealed significant increases in tidal volume , 
 inspiratory reserve volume , inspiratory capacity , and breathing capacity in the 
 experimental group . 
 these increases were greater in the experimental group than in the 
 control group . 
 [ conclusion ] in our study , the experimental group which performed diaphragm 
 respiration exercises showed a greater improvement in pulmonary function compared with the 
 control group . 
 it is hypothesized that greater improvement in pulmonary function is 
 expected if diaphragm respiration exercises are implemented taking into account the age of 
 the smokers .