in korea , 26.5% of the total female population is obese , and women in their 30s , 40s , and 50s account for 28% , 34.4% , and 37.4% , respectively , of the total obese female population .
a sharp increase in the prevalence of obesity has been particularly seen with onset of menopause , a time in which women experience many metabolic changes from female hormone fluctuations .
it has been reported that women are at higher risk for obesity during this period due to increases in body fat .
postmenopausal women , in particular , often develop abdominal obesity without weight change , due to excessive accumulation of visceral fat and hormonal changes in the abdomen . increased physical activity through regular exercise is very effective for mitigating obesity and improving health - related fitness at all ages [ 4 , 5 ] .
park et al .   reported that combined exercise , resistance exercise combined with aerobic training , is more effective for mitigating obesity than aerobic training alone .
recently , it was reported that gut microbiota is closely involved with obesity onset   and that endotoxins residing in gut flora are also closely correlated with visceral fat increases .
endotoxins promote the activation of inflammatory responses by stimulating microphages to secrete proinflammatory cytokines , including tumor necrosis factor- ( tnf- ) . during this process
the endotoxin receptor cd14 plays an important role in inflammatory and innate immune responses [ 1214 ] . as obesity can increase endotoxin levels , causing inflammatory responses , obese women can in turn suppress immune function . in this vein , various studies on controlling endotoxin levels and immune functions are being conducted , and interest in reducing endotoxins and improving immune functions through exercise is increasing [ 15 , 16 ] .
kim et al .   reported that the largest immune function improvements resulted from combined exercise when aerobic , resistance , and combined exercises were compared .
ng et al .   reported that there were no changes in concentrations of serum endotoxin and tnf- after a one - time 21  km road race .
reported that when 61 study participants performed high- and moderate - intensity aerobic exercise for 3040  min , 4 times a week for 12 weeks , only high - intensity exercise decreased the concentration of serum endotoxins .
clearly , there have been many studies about an acute bout of exercise and aerobic exercise on physical activity and immune functions , but there is a lack of studies on endotoxin concentration changes after combined physical exercise .
moreover , while there are many studies on obesity and inflammation , as well as exercise and immune functions , there are hardly any studies on the interplay between endotoxins , health - related fitness , and immune functions of postmenopausal women with abdominal obesity .
accordingly , this study was conducted to examine the effects of combined exercise on health - related fitness , endotoxin concentrations , and immune functions of postmenopausal women with abdominal obesity .
the participants in this study were naturally postmenopausal middle - aged women with abdominal obesity .
other selection criteria included a lack of regular exercise habits , no prior or present history of genital - related diseases , and not being under treatment for any internal or gynecological diseases .
as we explained above , 20 voluntary participants were randomly allocated to the combined exercise group ( n = 10 ) or the control group ( n = 10 ) . and
visceral obesity was defined as a visceral - to - subcutaneous fat ratio  0.4 based on computed tomography ( ct ) results .
the participants ' physical characteristics are summarized in table 1 . a body composition analyzer ( venus-5.5 , korea )
was used to measure the height , weight , % body fat , body fat , and lean body mass ( lbm ) before and after 12 weeks of exercise .
body mass index ( bmi ) was calculated using weight / height ( kg / m ) .
blood pressure was measured with a mercury sphygmomanometer ( hico , japan ) after participants were stabilized for 30  min .
exercise stress testing was conducted before and after 12 weeks of exercise , using the balke treadmill protocol .
maximal exercise stress was defined as the presence of any 2 of the following : ( 1 ) manifestation of steady state with oxygen intake not exceeding 150  ml / min and expected maximum heart rate ( 220-age ) ; ( 2 ) respiratory exchange ratio ( rer ) 1.15 ; and ( 3 ) ratings of perceived exertion ( rpe ) 17 .
oxygen intake and heart rate during exercise were analyzed with an automatic metabolic analyzer ( quarkb2 , cosmed , italy ) . in the week
prior to training , 1-repetition maximum ( 1rm ) measurements were taken , and resistance equipment training and treadmill acclimation exercises were performed .
the 1rm for resistance training was measured using the formula from the korea institute of science and technology . in weeks
16 , 60% of 1rm was used for 810 repetitions . in weeks 712 , 70% 1rm was used for 1012 repetitions .
each session lasted for 30  min 3 times a week . for aerobic training , exercise speed and heart rate based on the maximal exercise test were used to calculate the target heart rate ( thr ) , equivalent to 4075% of the heart rate reserve ( hrr ) , ( thr = hrr  intensity ( % ) + resting heart rate ) , after which the target exercise speed was determined with a regression equation each for 40  min 3 times a week for 12 weeks .
5102 ) . and also , total sit - ups and push - ups performed in 30 seconds were measured .
all measurements were taken twice , and the highest value was recorded . to measure abdominal fat ,
a ct scanner ( samsung ge sytec 3000 i ) scanned the transverse sections one above and one below umbilical level .
the area 's total abdominal fat volume was calculated by considering tissues with a hounsfield number from 250 to 50 to be fat . using abdominal and peritoneal spread as the boundary , the areas were divided into visceral fat tissue and subcutaneous fat tissue , with which the visceral fat to subcutaneous fat ratio was calculated . before and after program
, 15  ml of blood was drawn from the antecubital vein under fasting , stable conditions .
levels of total cholesterol ( tc ) , triglycerides , high - density lipoprotein cholesterol ( hdl - c ) , and low - density lipoprotein cholesterol ( ldl - c ) were analyzed enzymatically using an autoanalyzer ( hitachi 7600 - 110/7170 analyzer , tokyo , japan ) .
levels of tnf- , cd14 , and immunoglobulins ( iga , igg , and igm ) were analyzed using enzyme - linked immunosorbent assay ( elisa ) , flow cytometry , and immunoturbidimetry , respectively .
the spss statistics 18.0 program was used to calculate means and standard deviations for all variables .
significant differences between the exercise and control groups were determined with 2-way anova and paired t - tests . for independent correlation between changes in endotoxin and oxygen intake per weight ,
body composition and abdominal fat before and after the exercise program are given in table 3 . in the exercise group , visceral fat and the visceral to
subcutaneous fat ratio ( both p < 0.01 ) decreased significantly compared to preprogram values .
visceral fat ( f = 7.619 , p < 0.01 ) and the visceral to subcutaneous fat ratio ( f = 29.894 , p < 0.001 ) changed significantly over time and between groups . no control group variables changed after the program .
in the exercise group , a significant decrease was seen in postprogram % body fat ( p < 0.05 ) compared to preprogram values . grip strength ( p < 0.05 ) , push - ups ( p < 0.05 ) , and maximum oxygen intake per weight ( p < 0.01 ) increased significantly . moreover , % body fat ( f = 4.844 , p < 0.05 ) , grip strength ( f = 4.583 ,  p < 0.05 ) , push - ups ( f = 5.562 , p < 0.05 ) , and maximum oxygen intake per weight ( f = 7.555 , p
cholesterol , tnf- , and c - reactive protein ( crp ) level changes are given in table 5 .
in the exercise group , hdl - c level increased significantly following the 12-week program ( p < 0.05 ) , whereas tnf- level decreased significantly ( p < 0.05 ) .
moreover , hdl - c ( f = 9.728 ,  p < 0.01 ) and tnf- ( f = 5.147 , p < 0.05 ) levels changed significantly over time and between groups .
immune functions , cd14 , and endotoxin values from before and after the program are given in table 6 .
values of iga ( p < 0.01 ) and igg ( p < 0.05 ) increased significantly after program , whereas cd14 ( p < 0.05 ) and endotoxins ( p < 0.01 ) decreased significantly .
moreover , iga ( f = 8.333 , p < 0.01 ) , cd14 ( f = 5.434 , p < 0.05 ) , and endotoxin ( f = 8.963 , p
postmenopausal women often develop abdominal obesity without weight change from excessive accumulation of visceral fat in the abdomen , attributed to decreased lipolysis as a result of reduced estrogen . as a result , many postmenopausal women experience decreased lbm and increased % body fat , most frequently in the abdominal area .
are also more at risk from obesity than premenopausal women . that is , more severe abdominal obesity results in greater probability of metabolic disease development .
therefore , prevention and mitigation of abdominal obesity in middle - aged postmenopausal women are important .
kim et al .   reported that combined exercise and stretching ( 80  min sessions 5 times a week for 8 weeks ) reduced visceral fat in middle - aged obese women .
park et al .   reported that an aerobic exercise regimen ( 60  min sessions 5 times a week for 12 weeks ) reduced visceral fat in middle - aged men .
choi and chun   also reported that circuit training ( 60  min sessions 4 times a week for 12 weeks ) mitigated obesity . in the present study , a 90  min combined exercise session ( 10  min warm - up , aerobic exercise for 40 minutes , resistance exercise for 30  min ,
10  min cool - down ) was performed 3 times a week for 12 weeks , resulting in reduced visceral fat ( p < 0.01 ) and a reduced visceral to subcutaneous fat ratio ( p < 0.001 ) . in addition , a significant difference in results was seen between the control and exercise groups and over time , consistent with previous studies .
these results indicate that regularly performing combined exercise helps reduce visceral and subcutaneous abdominal fat in postmenopausal women .
the acsm   separates motor skill - related fitness from health - related fitness and divides health - related fitness into body composition , flexibility , muscle strength , muscle endurance , and cardiovascular endurance .
decline in any of these elements ' scan results in an increased likelihood of contracting a disease .
flexibility can reduce muscle and joint injuries , and increased cardiovascular endurance reduces the probability of developing cardiovascular diseases .
clearly , health - related fitness is very important in maintaining and improving the quality of daily life , a view supported by many studies .
kim et al .   reported that body fat , % body fat , and cardiorespiratory fitness improved in severely obese women as a result of a 12-week , low - intensity walking program .
shin et al .   reported that body fat , % body fat , muscle mass , cardiovascular endurance , muscle strength , and flexibility improved significantly in obese female college students as a result of dumbbell lifting and walking for 60  min sessions 4 times a week for 12 weeks .
although exercise type and intensity influence areas of improvement , most previous studies reported that exercise improved overall health - related fitness .
the 12-week combined exercise program reduced body fat and % body fat and improved cardiorespiratory fitness through aerobic exercise and also improved muscle strength and endurance by increasing lbm through resistance exercise .
it is thus considered appropriate exercise to improve obese people 's overall health - related fitness .
they do not exist independently in the blood but are transported combined with proteins in particle form as  lipoproteins . 
lipoproteins are classified as hdl - c ( transporting cholesterol from peripheral tissues to the liver for degradation ) or ldl - c ( accumulating cholesterol in the blood vessels ) .
obesity increases the prevalence of metabolic diseases , such as cardiovascular disease and insulin resistance , by raising these serum lipid levels , and hdl - c and ldl - c , in particular , are important indicators for prediction and evaluation of coronary artery diseases .
park et al .   reported significant increases in hdl - c and significant decreases in tc among serum lipids in middle - aged women with abdominal obesity after performing a combined exercise regimen of 60  min sessions 4 times a week for 12 weeks .
kang and jung   also reported significant decreases in tc and significant increases in hdl - c in obese people after an aerobic exercise regimen of 40-minute sessions 4 times a week for 12 weeks . in the present study ,
the exercise group 's ldl - c , tc , and tg values decreased , while hdl - c values increased .
although paek   reported that there were no significant differences in middle - aged women 's tc values after performing aerobic dance 4 times a week for 12 weeks , most studies reported positive improvements in serum tc and tg levels as a result of regular training .
in particular , hdl - c improvements , a cardiovascular risk factor , were seen in the present study .
we believe that combined exercise can strengthen cardiopulmonary functions and help prevent and mitigate cardiovascular diseases and hyperlipidemia from hdl - c caused obesity .
additionally , tnf- , one of the inflammatory cytokines and a primary modulator of systematic response to infectious diseases , is closely related to obesity .
its serum concentrations are known to increase during high - intensity exercise , and high levels of tnf- are secreted by adipose tissues .
samartn and chandra   reported that tnf- and tnf- gene activations , accompanied by weight loss , were observed in obese people .
conducted a 1-year weight - loss program with 56 middle - aged obese women and saw a significant tnf- decrease .
kondo et al .   reported significant decreases in tnf- in obese women after 7 months of slope jogging and walking .
this study 's decrease in tnf- levels was consistent with previous studies and is believed to result from reduced adipose tissue secretion of tnf- after combined exercise decreased body fat , % body fat , and visceral fat .
immunoglobulins ( iga , igg , and igm ) function as antibodies , carrying out humoral immune functions against antigens that invade the body .
iga is found mostly in saliva and stops bacteria or microorganisms from invading the body by binding to them at sites vulnerable to bacterial invasion .
the known normal values of immunoglobulins iga , igg , and igm are 160330  mg / dl , 7001400  mg / dl , and 60150  mg / dl , respectively .
reported that appropriate exercise increased the serum immunoglobulin concentrations , whereas mackinnon   found no effect .
reported that igm decreased significantly in middle - aged women following combined exercise for 12 weeks , and tennyson and friedman   reported significant increases in igg in middle - aged obese women after 12 weeks of nordic walking . in the present study ,
based on this study and previous studies , it is believed that the immunoglobulins concentrations differ according to exercise time and duration , intensity , and participant age .
the stimulated microphages secrete proinflammatory cytokines , such as tnf- , il-6 , and il-1 , sometimes triggering excessive innate immune responses and causing a variety of immune responses and diseases , as well as aggravating existing diseases [ 9 , 46 ] .
in addition , when concentrations of serum endotoxin exceed 2 to 3 times the normal level , it becomes difficult to modulate the extent of inflammation , which induces weight gain .
in other words , endotoxins are believed to be important obesity - related and metabolic disease risk factors .
while studies on endotoxins and exercise responses are lacking , the present study showed that visceral fat and endotoxin decrease after a 12-week combined exercise program .
lowered tnf- after exercise might have an important role in the obesity reduction and increased immune function .
in the present study , middle - aged , postmenopausal women with abdominal obesity performed 90 minutes of combined aerobic and resistance exercises 3 times a week for 12 weeks in order to examine the effects of combined exercise on health - related fitness , endotoxin levels , and immune functions .
we conclude that , as a result of the combined exercise program , abdominal fat , health - related fitness , immune response , and endotoxins all changed significantly over time and between groups .
as seen in the above results , the exercise group 's abdominal obesity was mitigated due to visceral fat reduction ; grip strength , push - ups , and oxygen intake per weight improved ; and hdl - c and iga increased , while tnf- , cd14 , and endotoxin levels decreased .
therefore , for middle - aged postmenopausal women with abdominal obesity , a 12-week combined exercise regimen improved % body fat and health - related fitness and increased immune function , while a decrease in visceral fat and endotoxin concentrations was seen .
accordingly , we believe that combined exercise is effective in mitigating abdominal obesity , preventing metabolic diseases , and enhancing immune function . additionally , endotoxins may be a potential risk factor for obesity .
lowered tnf- after exercise might have an important role in the obesity reduction and increased immune function .
in addition , making specific diet programs for postmenopausal woman to achieve a better control of variables on preventing metabolic diseases and mitigating obesity is urgently needed in the near future .
 this study was conducted to examine the effects of combined exercise on health - related fitness , endotoxin concentrations , and immune functions of postmenopausal women with abdominal obesity . 
 20 voluntary participants were recruited and they were randomly allocated to the combined exercise group ( n = 10 ) or the control group ( n = 10 ) . 
 visceral obesity was defined as a visceral - to - subcutaneous fat ratio 0.4 based on computed tomography ( ct ) results . 
 body composition , exercise stress testing , fitness measurement , ct scan , and blood variables were analyzed to elucidate the effects of combined exercise . 
 the spss statistics 18.0 program was used to calculate means and standard deviations for all variables . 
 significant differences between the exercise group and control group were determined with 2-way anova and paired   t - tests . 
 the exercise group 's abdominal obesity was mitigated due to visceral fat reduction ; grip strength , push - ups , and oxygen uptake per weight improved ; and hdl - c and iga level also increased , while tnf- , cd14 , and endotoxin levels decreased . 
 lowered tnf- after exercise might have an important role in the obesity reduction . 
 therefore , we can conclude that combined exercise is effective in mitigating abdominal obesity , preventing metabolic diseases , and enhancing immune function . 
1. Introduction
2. Study Methods
3. Results
4. Discussion
5. Conclusions