resistance exercise using weight machines or body weight builds muscle strength , helps 
 rehabilitate athletes , prevents injuries , and improves health in typical adults1 .
resistance exercises can be categorized 
 biomechanically into open kinetic chain ( okc ) and closed kinetic chain ( ckc ) exercises .
okc 
 exercises result in isolated movement at a given joint and are effective when isolated 
 strengthening for selected muscle groups is desired .
in contrast , ckc exercises cause 
 co - contraction of agonist and antagonist muscle groups2 , 3 .
okc and ckc exercises are 
 applied directly to everyday physical activities and exercise , and combined okc and ckc 
 training is recommended for treatment and rehabilitation1 .
thus , combined training is required not only for muscle strength 
 improvement but also for muscle stabilization
. meanwhile , resistance training increases oxygen supply and blood flow to skeletal muscles 
 when they are scarce ; this stimulates the growth of capillaries within the muscles and is 
 called angiogenesis4 , 5 .
angiogenesis factors include vascular endothelial growth factor 
 ( vegf ) , angiopoietin 1 ( ang 1 ) , and angiopoietin 2 ( ang 2 ) . the major functions of vegf are 
 to increase the growth and movement of vascular endothelial cells6 and to regulate capillaries within skeletal muscles7 .
ang 1 participates in 
 stabilization of blood vessels9 , whereas 
 ang 2 participates in destabilization and remodeling10 .
in addition , the skeletal muscle growth protein follistatin has a 
 positive effect on muscle growth by suppressing myostatin activity11 .
acute and regular aerobic exercise is reported to 
 upregulate angiogenesis factors10 , 12 , 13 . however , there are still only a few reports clarifying the effects 
 of regular resistance exercise on angiogenesis factors .
thus , it is essential to investigate the effects of combined okc and ckc training , which 
 can selectively strengthen muscle groups and improve muscle coordination , to determine 
 whether such training is effective for rehabilitation and improves the quality of physical 
 activity
. hence , the aim of the present study was to investigate the effects of combined okc 
 and ckc training on muscle strength , anaerobic power , and blood levels of angiogenesis 
 factors .
twenty male college students with no medical problems were randomly divided into pulley 
 training ( pt , n=10 ) and control ( co , n=10 ) groups . to obtain valid results ,
the subjects 
 were advised against participating in excessive physical and nonroutine social activities on 
 the day before the experiments .
food intake was prohibited after 21:00  h on the day before 
 the experiments , and fasting for more than 12  h was required for all subjects .
body 
 composition , including height , weight , body mass index ( bmi ) , percentage of body fat , and 
 lean body mass ( lbm ) , was assessed at the dong - a university laboratory using an established 
 bioelectrical impedance method with a venus 5.5 body composition analyzer ( jawon medical , 
 gyeongsangbuk - do , korea ) .
three days before the experiment , one repetition maximum ( 1rm ) was 
 performed to test the experiment by indirect methods14 .
all volunteers underwent medical screening , including a health 
 status interview and physical examination . written informed consent
the study was approved by dong - a university hospital s institutional review board , 
 and conducted in agreement with the declaration of helsinki .
the exercise program is shown in table 
 1table 1.combined open kinetic chain and closed kinetic chain training programs using 
 pulley exercise machinesitemcontentstime ( min)warm upstretching10 minokc ( 60% 1rm , 10 rep , 2 sets ) and ckc ( 10 rep , 2 sets ) 
 pulley trainingchest press40 minshoulder presspulley curlpush downlat pull downknee extensionreg curlcool downstretching10 min .
the training in this study was performed using pulley exercise machines 
 ( well - tech , busan , korea ) that can be used for okc and ckc training .
okc exercise was 
 performed for 8 weeks at 60% of 1rm , and the value of 1rm was recalibrated every 2 weeks . 

the order of exercise was 2 sets of 10 
 repetitions of okc exercise , followed by 2 sets of 10 repetitions of ckc exercise .
all 
 subjects performed a warm - up and cool - down 3 times to calibrate the measuring equipment . 

isokinetic strength testing for extension and flexion of the trunk ( 60/s ) and knee ( 60/s ) 
 was performed with humac norm dynamometer ( csmi , stoughton , ma , usa ) .
anaerobic capacity was 
 measured using a wingate test on a plate - loaded and friction - braked bicycle ergometer 
 ( monark , vansbro , sweden ) .
the items measured were average power ( ap ) , peak power ( pp ) , peak 
 pedaling speed ( pps ) , and peak attainment time ( pat ) . blood ( 10  ml ) was collected from 
 subjects via the antecubital vein for analysis of serum samples after a 12-h overnight fast . 

each blood sample was centrifuged for 15 minutes at 3,500  rpm at 4  c .
the supernatant was 
 decanted and stored in a deep freezer at 80  c until analysis .
serum total cholesterol 
 ( tc ) , high - density lipoprotein cholesterol ( hdl - c ) , free fatty acid ( ffa ) , and triglyceride 
 ( tg ) concentrations were assayed using an enzyme - linked immunosorbent assay ( elisa ) kit . 

low - density lipoprotein cholesterol ( ldl - c ) level was calculated with the following 
 equation15 : ldl - c = tc  hdl - c  tg/5.0 
 ( mg / dl ) .
vegf , ang 1 , ang 2 , and follistatin levels were analyzed using an elisa kit 
 ( r&d systems , minneapolis , mn , usa ) .
first , 100  l of capture antibody was incubated 
 overnight at room temperature and washed 3 times . the samples and
then , streptavidin - horseradish peroxidase and 
 substrate solution were added , the reaction was terminated with the stop solution , and 
 results were immediately obtained by optical density of each well using microplate reader 
 set to 450  nm16 . the mean and standard deviation of data obtained in our study
were calculated using the 
 spss statistics package for windows version 20.0 ( spss , armonk , ny , usa ) .
pre- and post - data 
 were analyzed using the paired t - test within - group differences and the independent t - test 
 for differences between the groups .
changes in body composition of subjects are shown in table 2table 2.physical characteristics of the subjectsvariablecoptprepostprepostheight ( cm)173.2  2.5173.5  2.5173.7  1.78174.1  1.6weight ( kg)66.5  2.767.5  2.868.8  2.769.5  2.6bmi ( kg / m)22.3  1.222.6  1.222.8  0.822.9  0.9body fat ( % ) 17.4  2.017.9  2.219.5  1.617.9  1.6*lbm ( kg)54.7  1.355.0  1.255.0  1.256.8
bmi : body mass index ; lbm : lean body mass ; co : control group ; pt : pulley training 
 group .
after 
 8 weeks of training , the results of the serum lipids test ( table 3table 3.lipid profilesvariablecoptprepostpreposttc ( mg / dl)154.4  8.2153.9  8.5158.8  13.9149.5  8.3tg ( mg / dl)75.6  5.470.8  4.972.2  3.855.2  2.4*#ffa ( eq / l)466.8  59.7512.9  74.1471.1  69.0499.6  38.1hdl - c ( mg / dl)51.6  2.551.7  1.950.6  1.447.5  1.6ldl - c ( mg / dl)87.7  8.688.0  9.993.7  13.888.9
 9.3values are meanse.co : control group ; pt : pulley training group*p<0.05 vs. pre , # p<0.05 vs. co ) were as follows : there was no significant difference according to time or 
 group for tc , ffa , hdl - c , and ldl - c , but tg decreased significantly after the exercise 
 ( p<0.05 ) .
the results for isokinetic muscle strength after 8 weeks of training are shown 
 in tables 4 and 5table 4.the results for trunk ( 60/s ) muscle strength after 8 weeks of trainingvariablecoptprepostprepostfpt ( nm)224.2  30.1218.2  25.9227.8  17.7298.7  19.7*#fpt%bw ( nm)291.8  20.5277.1  10.1274.8  19.9362.4  16.3*#fwr ( nm)139.7  10.9143.9  12.9143.2  13.4186.2  7.8*#fwr%bw ( nm)215.6  18.0196.3  12.4195.9  13.4261.3  15.3*#ept ( nm ) 250.9  8.1247.8  8.8232.3  9.6287.3  11.0*#ept%bw ( nm)329.9  19.2323.6  20.5362.8  19.2406.5  19.2*#ewr
( nm)249.9  12.8255.3  11.5256.5  11.3292.2  13.5*#ewr%bw ( nm)340.4  24.7317.8  23.4364.4  24.4422.1  19.0*#values are meanse .
fpt : flexor peak torque ; fpt%bw : fpt per body weight ; fwr : flexor work per 
 repetition ; fwr%bw : fwr per body weight ; ept : extensor peak torque ; ept%bw : ept per 
 body weight ; ewr : extensor work per repetition ; ewr%bw : ewr per body weight ; co : 
 control group ; pt : pulley training grouptable 5.the results for knee ( 60/s ) muscular strength after 8 weeks of trainingvariablecoptprepostprepostfpt ( nm)88.8  8.382.2  10.283.2  6.8105.3  5.8*#fpt%bw ( nm)129.0
 11.1120.7  13.9123.2  9.6154.3  9.2*#fwr ( nm)109.4  8.0107.8  9.7109.6  8.5130.2  9.2*#fwr%bw ( nm)161.2  12.8154.9  12.4162.6  11.2198.1  11.6*#ept ( nm)161.4  13.8166.6  7.4168.5  10.2197.9  8.1*#ept%bw ( nm)242.1  15.1244.4  14.2245.2  9.3277.5  9.2*#ewr ( nm)182.9  7.9183.2  9.5184.5  8.5224.4  11.4*#ewr%bd ( nm)264.7  14.9266.7  16.7268.1  11.5303.7
 12.4*#values are meanse.fpt : flexor peak torque ; fpt%bw : fpt per body weight ; fwr : flexor work per 
 repetition ; fwr%bw : fwr per body weight ; ept : extensor peak torque ; ept%bw : ept per 
 body weight ; ewr : extensor work per repetition ; ewr%bw : ewr per body weight ; co : 
 control group ; pt : pulley training group.*p<0.05 vs. pre , # p<0.05 vs. co. after 8 weeks of training , muscle strength in the flexors and extensors of 
 the trunk ( 60/s ) and knee ( 60/s ) were improved ( p<0.05 ) . the anaerobic power of each 
 group is shown in table 6table 6.the anaerobic power of each groupvariablecoptprepostprepostap ( w)535.1  16.2540.9  19.9557.8  17.2597.6  12.8*pp ( w)672.8  32.2696.2  34.7675.7  21.3741.3  21.8*pps ( rpm)138.8  6.9142.4  5.1134.3  3.8146.3  4.9*pat ( s)6.6  0.66.5  0.710.8  1.58.09
ap : average power ; pp : peak power ; pps : peak pedaling speed ; pat : peak attainment 
 time ; co : control group ; pt : pulley training group .
ap , pp , and pps increased significantly for the pt group after training 
 compared to before training ( p<0.05 ) .
the changes in angiogenesis factors and follistatin 
 after 8 weeks of training are shown in table 
 7table 7.the changes in angiogenesis factors and follistatin after 8 weeks of 
 trainingvariablecoptprepostprepostvegf ( pg / ml)47.0  1.347.7  0.950.3  3.052.8  4.0*ang 1 ( pg / ml)403.9  29.2504.7  24.0 *
 0.716.3  0.7follistatin ( pg / ml)22.2  3.824.9  2.823.7  3.429.1  3.9*values are meanse .
vegf : vascular endothelial growth factor ; ang 1 : angiopoietin 1 ; ang 2 : angiopoietin 
 2 ; co : control group ; pt : pulley training group .
ang 1 increased 25% in the co group ( p<0.05 ) and 48% in the pt group 
 ( p<0.05 ) after training .
vegf and follistatin also increased significantly after training 
 in the pt group ( p<0.05 ) .
bmi : body mass index ; lbm : lean body mass ; co : control group ; pt : pulley training 
 group .
* p<0.05 vs. pre co : control group ; pt : pulley training group * p<0.05 vs. pre , # p<0.05 vs. co values are meanse .
fpt : flexor peak torque ; fpt%bw : fpt per body weight ; fwr : flexor work per 
 repetition ; fwr%bw : fwr per body weight ; ept : extensor peak torque ; ept%bw : ept per 
 body weight ; ewr : extensor work per repetition ; ewr%bw : ewr per body weight ; co : 
 control group ; pt : pulley training group fpt : flexor peak torque ; fpt%bw : fpt per body weight ; fwr : flexor work per 
 repetition ; fwr%bw : fwr per body weight ; ept : extensor peak torque ; ept%bw : ept per 
 body weight ; ewr : extensor work per repetition ; ewr%bw : ewr per body weight ; co : 
 control group ; pt : pulley training group . * p<0.05 vs. pre , # p<0.05 vs. co values are meanse .
ap : average power ; pp : peak power ; pps : peak pedaling speed ; pat : peak attainment 
 time ; co : control group ; pt : pulley training group .
vegf : vascular endothelial growth factor ; ang 1 : angiopoietin 1 ; ang 2 : angiopoietin 
 2 ; co : control group ; pt : pulley training group .
muscle strength and function are affected by muscle atrophy with aging , musculoskeletal 
 disorders , sedentary living , and bed confinement17 , 
 18 .
however , regular resistance 
 exercise improves muscle function , increases strength after damage , and prevents decline in 
 muscle strength despite aging19 , 20 . in particular ,
combined okc and ckc 
 training can be considered essential for muscle strength improvement and stabilization . 

hence , the present study analyzed the effect of using pulley exercise machines that enable 
 combined okc and ckc training on muscle strength anaerobic power and angiogenesis 
 factors .
eight weeks of this combined training was effective in significantly increasing muscle 
 strength in the flexors and extensors of the trunk and knee ( p<0.05 ) .
this is consistent 
 with previous studies reporting that resistance exercise increases muscle strength12 , 21,22,23 . 

anaerobic exercise capacity refers to the muscle endurance and contractile strength that 
 results from anaerobic metabolism and is highly correlated with strength and endurance24 .
a 30-s wingate anaerobic exercise 
 capacity assessment method is widely used to determine anaerobic power . in this study ,
the 
 anaerobic ap and pp results after 8 weeks of combined ock and ckc training using pulley 
 exercise machines improved significantly in the pt group compared to the co group 
 ( p<0.05 ) .
these results are consistent with previous reports that the 30-s wingate 
 anaerobic test increased pp values after resistance training25 .
the density and ratio of capillaries in muscle of vegf - deficient mice were reportedly 
 lower26 .
previous studies reported that 
 angiogenesis in human and animal muscle tissue was induced by exercise27,28,29,30 .
gavin et 
 al.31 reported that acute knee extensor 
 exercise at an intensity of 6080% increased blood vegf mrna and vegf protein levels between 
 2 and 4  h after exercise .
yeo et al.16 
 reported that resistance exercise for 8 weeks at 60% or 90% intensity increased serum vegf 
 level in both groups .
the present study showed that blood vegf levels increased 
 significantly after 8 weeks of combined okc and ckc training using pulleys ( p<0.05 ) , 
 which was consistent with previous studies .
the stability of capillaries is reportedly promoted when the concentration of 
 ang 1 is higher than that of ang 2 and is reduced when the concentration of ang 2 is higher 
 than that of ang 132 , 33 .
ang 2 levels in this study did not change in either group . 
 however , ang 1 increased in the pt group . therefore , 8 weeks of combined okc and ckc 
 training can increase ang 1 and may be more effective in promoting capillary stability 
 compared to the co group .
follistatin increase muscle mass and promotes muscle growth by neutralizing myostatin , 
 which has a negative effect on mass and growth34 , 
 35 .
muscle mass increased in 
 follistatin - overexpressing transgenic mice and reduction in follistatin caused a decrease in 
 gastrocnemius mass36 .
acute knee extension in 
 postmenopausal women increased follistatin levels in skeletal muscle , and resistance 
 training at 8590% intensity increased serum follistatin levels and muscle strength37 .
the results of the present study showed a 
 significant increase in follistatin in the pt group ( p<0.05 ) after 8 weeks of combined 
 training .
the results of this study indicate that 8 weeks of combined okc and ckc training using 
 pulley exercise machines increased serum vegf , ang 1 , and follistatin and improved ap and pp 
 in tests of anaerobic capacity . the training also improved flexor and extensor strength in 
 the trunk and knee .
hence , 8 weeks of combined training effectively increased biochemical 
 factors that are closely related to muscle growth and improved muscle strength in the trunk 
 and knee .
future studies are needed to perform histological analysis of neuromuscular 
 activation , muscle hypertrophy , and angiogenesis factors following combined training .
 [ purpose ] this study investigated the effects of combined open kinetic chain and closed 
 kinetic chain training using pulley exercise machines on muscle strength , anaerobic power , 
 and blood levels of angiogenesis factors . 
 [ subjects and methods ] twenty male university 
 students were equally divided between control and pulley training groups . 
 the 
 pulley - training group underwent 8 weeks of combined training . 
 open kinetic chain training 
 consisted of 2 sets of 10 repetitions at 60% of one repetition maximum ; closed kinetic 
 chain training consisted of 2 sets of 10 repetitions of resistance exercise using the 
 subject s own body weight . 
 isokinetic strength ( trunk and knee ) , anaerobic power , vascular 
 endothelial growth factor , angiopoietin-1 , angiopoietin-2 , and follistatin were analyzed . 
 
 [ results ] after 8 weeks , flexor and extensor muscle strength significantly increased in 
 the trunk and knee ; average and peak power also increased significantly . 
 angiopoietin 1 
 increased 25% in the control group and 48% in the pulley training group ; vascular 
 endothelial growth factor and follistatin increased significantly in the pulley - training 
 group after 8 weeks . 
 [ conclusion ] eight weeks of combined training using pulley exercise 
 machines effectively increased biochemical factors related to muscle growth , as well as 
 muscle strength in the trunk and knees . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION