a throwing event is a sports competition that displays a player s ability to throw an 
 object , such as a shot put , discus , javelin , or hammer . to achieve a high level of 
 performance in this sport , total physical fitness , including explosive muscle power , 
 flexibility , agility , and coordination is required1 . in particular , core and low extremity muscles are considered to be 
 important muscles for creating a greater rotatory force and maximum speed2 , 3 . the core muscle is found to improve the performance of athletes by increasing balance , as 
 well as trunk and lower extremity strength in various sports , including short - distance 
 running , volleyball , and golf , as core muscle training exercises enhance the stability of 
 the lumbus and spine balance by increasing the musculus transversus abdominis 
 contraction4,5,6,7,8,9 . thus , the core exercise 
 program , which maximizes the mobility and stability of the core muscles , is greatly 
 emphasized for athletes11 . although previous studies examined the effect of core exercises on isokinetic muscle 
 functions in various sports5,6,7,8 , 12 , only limited studies are 
 available to establish an effective and practical muscle training program focusing on 
 throwing events in particular . therefore , this study aimed to investigate the effect of 
 peculiar complex core balance training on isokinetic muscle function of the knee joint and 
 lumbus to provide fundamental data for establishing a training program that improves the 
 performance and prevention of injury by developing the core and low extremity muscles . a total of ten high school athletes , who have been performing in throwing events for over 
 five years , participated in this study . the subjects were randomly divided into two groups : 
 the experimental group ( n=5 ) and the control group ( n=5 ) . the experimental group underwent 
 peculiar complex core balance training ( 60  min / three times a week/16 weeks ) while the 
 control group did not participate in such training . all subjects were educated about the 
 content and purpose of the experiment and provided written informed consent before beginning 
 the study . a peculiar complex core balance training program was established based on 
 previous studies13 with two sports 
 training and conditioning experts , and three current throwing coaches ( table 1table 1.peculiar complex core balance training programstage 1 ( week 14 ) programcore exercisesling exercisestraight leg lifts , twisted waist oblique crunches , butt raises , 
 shoulder - to - knee leg overs , side to side planks , plank with hip drops , around the 
 world plank , bridge plank , straight plank , mountain climbers , side plank hip 
 abduction with a twist , spiderman plank , side planks with reachsuspended plank , suspended single plank , suspended double pike , 
 reverse , climber , outsiders , roll - outs , bicep curl , push curl , single - leg lunge , 
 hamstring curl , hip  raise , oblique twist , tricep extension , rear deltoid , 
 captain america workout intensity = rpe 1314 , 10 rep  3 set ; duration = 50 
 min ; rest = 1 min between setstage 2 ( week 510 ) programcore exercisesling exercisesky reachers , sit - up , feet up crunch , bicycle pausers , fast 
 bicycles , extended reverse crunch , compound push up , burpees , dynamic push up , 
 leaping lunges , bring knee to elbow on the way down , ski abs , plank squatsbicep curl , push curl , single - leg lunge , hamstring curl , hip raise , oblique twist , tricep extension , rear deltoid , captain america workout , 
 suspended crunch 1 & 2 , pendulum 1 & 2 , standing body crunch , standing 
 oblique twist , suspended oblique crunchintensity = rpe 1314 , 15 rep  3 set ; duration = 60 
 min ; rest = 1 min between setstage 3 ( week 1116 ) programcore exercisesling exercisesingle rowers , supermans , oppo - raisers , bird dogs , throw downs , hip 
 to hip , hand walk - outs , , bicycle pausers , plank push up , side plank rotation , 
 side planks reach throughs , tricep dip oblique crunches , hip thrust , grass 
 hoppers , russian twist , bicycle crunchbicep curl , push curl , single - leg lunge , hamstring curl , hip raise , oblique twist , tricep extension , rear deltoid , captain america workout , 
 suspended crunch 1 , suspended crunch 2 , pendulum 1 , pendulum 2 , standing body 
 crunch , standing oblique twist , suspended oblique crunchintensity = rpe 1314 , 20 rep  3 set ; duration = 60 
 min ; rest = 1 min between set ) . the training consisted of 16 weeks of mat , medicine ball , and sling training , focusing on 
 the development of core muscles with three stages , including basic balancing and muscle 
 adaptation ( 4 weeks ) , kinetic balancing and muscle development ( 6 weeks ) , and complex 
 training of kinetic balancing and muscle development ( 6 weeks ) . the intensity of training 
 was decided by rating the perceived exertion ( rpe)14 . in this study all subjects 
 underwent measurement of the lower extremity ; lumbus muscular strength was measured by 
 isokinetic measurement equipment ( cyber-770 , lumax . all experiments were thoroughly 
 reviewed and approved by the institutional review board of daegu university . the means and standard deviations of the two groups 
 were calculated , and the analysis of covariance ( ancova ) was conducted to examine the 
 differences between the groups and between measurement time points . the results of the ancova indicate a significant effect of peculiar complex core balance 
 training and difference between the experimental and control groups . first , in terms of the 
 change of isokinetic strength of the knee joint , ancova [ between - subjects factor : group 
 ( experimental , control ) ; covariate : time ( pre - post ) ] revealed the main effects of group and 
 time in all measurements ( p<0.05 ) , excluding extension of muscle power ; the interaction 
 between group and time in extension of muscle power was also significant ( p<0.05 ) ( table 2table 2.result of ancova for knee joint strength and muscle powertypeexperimental groupcontrol group strength ( nm)lextensionpre254.614.2258.121.6post268.417.3260.219.7**flexionpre207.011.6198.311.2post224.913.6201.218.3*rextensionpre268.420.3257.421.6post270.719.1256.396.0**flexionpre181.618.3189.614.2post210.121.3194.415.7*muscle power ( nm)lextensionpre57.214.154.110.5post72.112.156.911.2**flexionpre145.210.1143.516.3post158.213.8143.817.1*rextensionpre68.117.269.810.1post75.116.370.120.7**flexionpre156.210.1158.109.1post162.209.3158.417.3*values are meansd . significantly different ( * * p<0.01 , * p<0.05 ) from the 
 experimental group . significantly different ( p<0.05 ) between pre and 
 post in the experimental group . significant interaction ( p<0.05 ) 
 between group and time in the experimental group ) . values are meansd . significantly different ( * * p<0.01 , * p<0.05 ) from the 
 experimental group . significantly different ( p<0.05 ) between pre and 
 post in the experimental group . significant interaction ( p<0.05 ) 
 between group and time in the experimental group secondly , regarding the change of isokinetic strength of the lumbus , ancova 
 [ between - subjects factor : group ( experimental , control ) ; covariate : time ] revealed the main 
 effects of group and time in all measurements ( p<0.05 ) ; the interaction between groups 
 and time in flexion of strength ( p<0.05 ) and extension of muscle power ( p<0.05 ) were 
 also significant ( table 3table 3.results of ancova for lumbus strength and muscle powertypeexperimental groupcontrol groupstrength ( nm)extensionpre297.121.8288.222.3post317.119.3291.322.0**flexionpre334.217.7335.220.1post359.219.1339.219.2*muscle power ( nm)extensionpre354.122.6361.220.2post369.118.0368.111.2**flexionpre321.114.2319.220.2post342.220.1324.116.3*values are meansd . significantly different ( * * p<0.01 , * p<0.05 ) from the 
 experimental group . significant interaction ( p<0.05 ) 
 between group and time in the experimental group ) . therefore , the isokinetic muscle function of the knee joint and the lumbus 
 in the experimental group was significantly increased compared to the control group . values are meansd . significantly different ( * * p<0.01 , * p<0.05 ) from the 
 experimental group . significantly different ( p<0.05 ) between pre and 
 post in the experimental group . core exercises mostly include the raising of legs and arms in the supine position to create 
 resistance in the abdomen and waist . core muscle training also helps athletes develop and 
 maintain total body balance . throwing , in particular , requires the creation of a unified 
 movement by connecting various steps of positions to maximize the performance , and the core 
 muscles are especially important1 . strong 
 core muscle training is especially important to improve the distribution of kinetic 
 efficiency to the whole body15 . core 
 muscle training improves the following fitness components : muscle strength , endurance , 
 agility , speed , balance , and the nervous system , including the vestibular system and the 
 proprioceptive system4 , 16,17,18 . in this study , peculiar complex core balance training 
 significantly increased the isokinetic strength of the knee joint and lumbus . this result is 
 consistent with previous studies , which suggest a positive effect of core muscle training on 
 the lower extremity and lumbus muscle reinforcement5,6,7,8 , 12 . according to yang s study12 , a 12-week 
 core training increased isokinetic muscle power of the knee joint and lumbar in 
 short - distance athletes . kim and chung5 
 conducted a 10-week core exercise program for athletes , and found lumbar strength increased . a study by shin , kim , and park6 showed 
 that a 4-week core exercise program had a positive impact on lumbar strength in golfers . han , kim , and hyun7 reported that a 
 12-week specificity core balance training increased the isokinetic muscular functions of the 
 knee joint and lumbar in high school volleyball players . moreover , song and hong s 
 study8 indicated that an 8-week core 
 strengthening program had a positive impact on knee extensor and flexor muscular strength in 
 college baseball players . in conclusion , this study found a positive effect on peculiar complex core balance training 
 on the isokinetic muscle functions of the knee and lumbus in throwing event athletes . therefore , core balance training would improve the performance of throwing event athletes by 
 improving balance and distribution of kinetic energy through the arms and legs . hence , 
 establishing an effective core training program that incorporates a mat , medicine ball , and 
 sling training , as this study has utilized , is required for athletes . it is also worthy to 
 note that this kind of core balance training prevents injury as well . although the results 
 of this study indicated that peculiar complex core balance training develops the isokinetic 
 muscle function in throwing event athletes , more specific and diverse research is necessary 
 to identify how exercises can be integrated into an ideal physical activity program that 
 caters to each athlete s own characteristics ( e.g. , age , gender , exercise career , and etc . ) 
 and type of sport .