the decreases in the fertile and pregnant populations and birth rate have accelerated the 
 aging of korean society , resulting in an increase in the elderly population . with the 
 increase in the elderly population , increased attention
should be given to the middle - aged 
 population , which includes people in the stage prior to the old age1 .
physical , psychological , and mental factors of middle age directly or indirectly affect the 
 quality of life in old age .
therefore , a 
 healthy old age life can stem from a well - managed and balanced middle age life .
moreover , 
 health in middle age is being emphasized in south korea aging society .
middle - aged women experience gradual weakening of physical functions with aging and show 
 decreased physical activities .
this decrease increases the obesity rate , causing middle - aged 
 women to be susceptible to various musculoskeletal problems such as osteoporosis and other 
 degenerative diseases2 .
moreover , 
 postmenopausal middle - aged women have reduced ovary functions due to estrogen deficiency , 
 and the level of low - density lipoprotein cholesterol ( ldl - c ) in the blood increases due to 
 reduced estrogen stimulation and low - density lipoprotein ( ldl ) receptor activities . in 
 addition , they are susceptible to adult diseases such as coronary diseases because of a 
 rapid increase in the lipid concentration in the blood and subsequent decrease in the 
 high - density lipoprotein - cholesterol ( hdl - c ) concentration3 .
regular aerobic exercises are suggested for middle - aged and older women to help them 
 overcome their physical and physiological changes and stabilize their mental and 
 psychological status through participation in society activities4 . among the aerobic exercises , walking is the most popular 
 physical activity , and it can be done easily without the use of any devices .
physical and 
 physiological improvements through walking exercise have been shown in a number of studies , 
 and positive influences are observed in most cases .
hence , walking can be an effective 
 exercise from the perspective of preventive medicine . yet
studies on the effects of walking 
 on blood and physical factors in obese middle - aged women have not been conducted 
 sufficiently5 .
this study was conducted to identify the effects of walking on the body composition , 
 health - related physical fitness , and serum lipids as part of efforts to encourage 
 middle - aged people to participate in walking as a regular and sustainable exercise .
the study period was 
 for 12 weeks from january to march 2010 . the participants were 43 middle - aged women ( age 
 range : 4055  years ) residing in seoul , korea , with body fat rates over 30% .
subjects in the 
 experiment group participated in the walking exercise ( n = 38 ) , whereas the control group 
 did not participate in the exercise ( n = 23 ) .
the participants had not undergone any 
 exercise regimen within the previous 1  year .
subjects who could not undergo the exercise 
 tests because of cardiac infarction and pulmonary embolism , confirmed using a self - answered 
 questionnaire , were excluded .
this study was approved by the seodaemun district office and 
 the institution in which it was performed and complied with the ethical standards of the 
 declaration of helsinki .
all participants provided their written informed consent to 
 participate in this study prior to enrollment .
general characteristics of the participantsexercise group ( n=38)control group ( n=23)age ( year)46.83.146.72.8height ( cm)159.13.7157.44.6weight ( kg)58.68.756.49.0blood pressuresystolic ( mmhg)124.014.2117.79.5diastolic ( mmhg)78.011.473.409.1*p<0.05 ; * * p<0.01 ; * * * p<0.001 . * p<0.05 ; * * p<0.01 ; * * * p<0.001 this study evaluated the body composition , physical fitness , and serum lipid level .
body 
 composition was evaluated by measuring body weight , muscle mass , and body mass index ( bmi ) . 

physical fitness was evaluated by measuring muscle strength , flexibility , muscle endurance , 
 and cardiopulmonary endurance .
muscle strength was determined by measuring the maximum grip 
 strength by using the dominant hand ( pf / kg ) .
flexibility was measured by a sit - and reach , in 
 which the subject sat with the knees completely straight and reached forward slowly using 
 both the hands together ( unit : cm ) . muscle endurance was measured through and exercise test 
 using sit - ups , and the maximum number was recorded for 30  s after a beep ( unit : number ) . 
 cardiopulmonary endurance was measured using a treadmill and a gas analyzer ( qmc 5000 , usa ) . 

the bruce protocol was used for the exercise test , and the maximum exercise point of the 
 participant was set at the maximum heart rate and a respiratory exchange rate of over 1.15 
 for each age range .
the indicator for cardiopulmonary endurance was the point where oxygen 
 intake did not increase even with an increase in exercise intensity . for serum
lipid test , 
 the participants fasted from 10:00 ( am ) of the previous day , and 5  ml of blood was collected 
 from the brachial vein the following day between 08:00 and 10:00 am .
after blood collection , 
 the vials were centrifuged , and tc , tg , hdl - c , and ldl - c levels were analyzed in the 
 hemanalysis department .
the walking program was designed such that the number of calories burned was gradually 
 increased to 150  kcal / hr by reducing the weight and increasing the walking speed .
the 
 initial exercise duration was 20  min , which was gradually increased to 4055  min ; the 
 initial frequency was 3 times a week , which was increased to 5 times a week .
details of the 
 walking durations and frequencies are shown in table 
 2table 2 .
twelve - week walking exercise programperiodintensityduration ( break)frequency03 weeks100  kcal / h20  min/23 times ( 5  min)3 times / week49 weeks120  kcal / h30  min/23 times ( 5  min)4 times / week1012 weeks150  kcal / h40  min/2 times ( 5  min)5 times / week .
two - way repeated anova was 
 used to observe the differences in each measurement factor by group ( exercise and control 
 groups ) and measurement period ( before and after the 24-week walking exercise program 
 participation ) .
a paired t test was conducted to confirm the significance of the measured 
 categories of before and after intervention in each group , and all statistical significance 
 (  ) was set at p < 0.05 .
regarding the changes in body composition , weight significantly decreased in the exercise 
 group ( p < 0.05 ) .
no main effect was observed by group ( exercise and control groups ) ; 
 however , main and interaction effects ( p < 0.05 ) were observed by period ( before and 
 after 12 weeks ) and period and group ( period*group ) .
muscle mass significantly decreased in 
 the exercise group ( p < 0.05).no main effect was observed by group ( exercise and control 
 groups ) ; however , main and interaction effects ( p < 0.05 ) were observed by period ( before 
 and after 12 weeks ) and period and group ( period*group ) .
further , main and interaction effects were observed by 
 group ( exercise and control groups ) , period , and period*group ( table 3table 3 .
changes in body compositionitemgrouppretestposttestweight ( kg)exercise58.58.657.27.3***control56.49.056.69.1muscle mass ( kg)exercise37.34.038.03.8control36.74.436.74.3body fat ( % ) exercise32.53.625.54.5***control31.23.731.03.6p value of paired t - test : * p<0.05 ; * * p<0.01 ; * * * p<0.001 .
p value of two - way 
 anova test ( period*group ) : p<0.05 ; p<0.01 ; 
 p<0.001 ) .
p value of paired t - test : * p<0.05 ; * * p<0.01 ; * * * p<0.001 .
p value of two - way 
 anova test ( period*group ) : p<0.05 ; p<0.01 ; 
 p<0.001 reagarding changes in physical fitness , no significant change was observed in grip strength 
 ( dominant hand ) in the exercise and control groups ( p > 0.05 ) .
further , no main and 
 interaction effects ( p > 0.05 ) were observed by group , period , and period*group .
no 
 significant change was observed with regard to performance of sit - ups in the exercise and 
 control groups ( p > 0.05 ) ; however , partial improvements were observed in the exercise 
 group .
further , no main and interaction effects were observed by group , period , and 
 period*group ( p > 0.05 ) , ( table 4table 4 .
changes in physical fitnessitemgrouppretestposttestgrip strengthexercise27.73.727.14.8control27.954.127.75.9sit - and- reachexercise15.46.616.85.6**control15.64.615.55.6sit - upexercise8.64.39.13.9control8.54.48.84.3vo2maxexercise24.43.526.94.6***control24.94.624.73.1p value of paired t - test : * p<0.05 ; * * p<0.01 ; * * * p<0.001 .
p value of two - way 
 anova test ( period*group ) : p<0.05 ; p<0.01 ; 
 p<0.001 ) .
p value of paired t - test : * p<0.05 ; * * p<0.01 ; * * * p<0.001 .
p value of two - way 
 anova test ( period*group ) : p<0.05 ; p<0.01 ; 
 p<0.001 regarding changes in serum lipids , tc showed a significant decrease in the exercise group 
 ( p < 0.05 ) , and main and interaction effects ( p < 0.05 ) were observed by group , 
 period , and period*group .
tg showed a significant decrease in the exercise group ( p < 
 0.05 ) , and main and interaction effects were observed by group , period , and period*group ( p 
 < 0.05 ) .
hdl - c showed a significant change in the exercise and control groups ( p > 
 0.05 ) , but main and interaction effects were not observed by group , period , and period*group 
 ( p > 0.05 ) .
ldl - c showed a significant decrease in the exercise group ( p < 0.05 ) , and 
 main and interaction effects were observed by group , period , and period*group ( p < 0.05 ) 
 ( table 5table 5 .
changes in serum lipiditemgrouppretestposttesttotal cholesterol ( mg / dl)exercise212.232.2176.729.1control209.734.4209.032.7triglyceride ( mg / dl)exercise183.258.8138.840.0control185.345.8187.546.1hdl - c ( mg / dl)exercise56.517.455.616.1control60.816.461.116.6ldl - c ( mg / dl)exercise128.016.9111.312.0control130.120.0129.816.6p value of paired t - test : * p<0.05 ; * * p<0.01 ; * * * p<0.001 .
p value of two - way 
 anova test ( period*group ) : p<0.05 ; p<0.01 ; 
 p<0.001 ) .
p value of paired t - test : * p<0.05 ; * * p<0.01 ; * * * p<0.001 .
p value of two - way 
 anova test ( period*group ) : p<0.05 ; p<0.01 ; 
 p<0.001
regular aerobic exercise in middle age increases the metabolic rate and improves risk 
 factors such as obesity , hypertension , and hyperlipidemia . in addition
, the functioning of 
 the heart and blood vessels improves so cardiovascular diseases such as coronary diseases 
 are prevented or delayed , thereby preventing various health problems in middle - aged 
 women6 , 7 .
the study results showed a significant decrease in weight and body 
 fat in the exercise group that participated in the 12-weeks of walking exercise . in the study by nindel et al .
( 2000 ) , weight and body fat were significantly decreased as a 
 result of 24 weeks of aerobic exercise 5 times a week8 .
jang ( 2009 ) reported that the weight , body fat , and muscle mass 
 decreased significantly in middle - aged women who participated in boxing aerobics9 . in the studies of park ( 2009 ) and park 
 ( 2011 ) on body composition , significant decreases in weight and body fat
were shown , which 
 implies that aerobic exercise and walking affects the body composition of participants5 , 10 . 

this result is considered to be due to the high breakdown rate of lipids through exercise ; 
 lipid usage is increased through an oxidation process , resulting in the reduction of weight 
 and body fat11 , 12 .
cholesterol ( tc , hdl - c , and ldl - c ) is a serum lipid found in the blood along with neutral 
 fat and phospholipids .
an increase in serum lipids expedites arteriosclerosis and is one of 
 the main reasons for cardiovascular diseases13 .
in particular , this lipid is a risk factor for adult diseases in 
 middle - aged women having reduced female hormone levels and physical fitness because of 
 decreased physical activities caused by aging .
significant decreases in tc , tg , and ldl - c 
 levels an increase in hdl - c level , although not significant , were observed after the 12-week 
 walking program in this study . in the study of ju ( 2010 ) on the influence of a 12-week - walking pilates program in 
 middle - aged women , the serum lipid , tc , tg , and ldl - c levels reduced significantly , and the 
 hdl - c showed no significant increase14 . 
 on the other hand , in the study kim ( 2009 ) , significant decreases in tc , tg and lds - c and 
 significant increases in hdl - c levels were observed in obese women after a 24-week walking 
 with running exercise program15 .
we 
 assume that a significant increase in hdl - c was not observed in this study because of a 
 difference in the exercise period and intensity .
both this study and the study of ju ( 2010 ) 
 were conducted for 12 weeks , whereas the study of kim ( 2009 ) was for 24 weeks and was a 
 combination program of walking and running exercises15 .
generally , significant changes in serum lipid levels are observed because aerobic exercise 
 blocks the ldl - c from accumulating on the arterial walls and facilitates the tc removal 
 mechanism in various cells , including smooth muscles in arteries , through increased hdl - c 
 levels , anti - arteriosclerosis , and catabolism during the transport of cholesterol to the 
 liver .
   [ purpose ] this study was conducted to identify the effects of walking on the body 
 composition , health - related physical fitness , and serum lipids as part of efforts to 
 encourage middle - aged people to participate in walking as a regular and sustainable 
 exercise . [ methods ] 
 this study was conducted as a pretest - posttest control group study . 
 
 the study period was for 12 weeks from january to march 2010 . 
 the participants were 43 
 middle - aged women ( age range : 4055  years ) with body fat rates over 30% . 
 subjects in the 
 experiment group participated in the walking exercise ( n = 38 ) , the control group did not 
 participate in the exercise ( n = 23 ) . 
 [ results ] in the exercise group , statistically 
 significant reductions in weight and body fat were observed among the body composition 
 measurement variables , and statistically significant increases in flexibility and 
 cardiopulmonary endurance were observed among the physical fitness measurement variables . 
 
 tc , tg , and ldl - c levels in the serum lipid measurement variables showed a statistically 
 significant reduction in the exercise group . [ conclusion ] the results of this study showed 
 that 12 weeks of walking exercise influenced middle - aged women in a positive way by 
 effecting changes in their body composition , physical fitness , and serum lipids . 
 we 
 believe that these positive changes result in positive effects on the factors for 
 prevention of various adult diseases that can occur in middle - aged women . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION