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Paper text:
for elite weightlifters , the enhancement of strength and balance plays a critical role in 
 their performance , since they must control extremely heavy weights above their head height 
 for a couple of seconds , while their arms are fully extended .
any kind of muscle imbalance 
 and inappropriate technique may hamper athletes ' performance and lead to dangerous 
 situations . however , a prolonged clean , jerk motion , which is thought to be the fundamental 
 movement for weightlifting seems to aggravate muscular imbalances leading to higher injury 
 incidence .
balance is generally defined as the ability to maintain the body 's center of gravity within 
 its base of support and may be categorized by either static or dynamic balance1 , 2 .
optimal 
 posture control requires sensory information from the visual , vestibular , and proprioceptive 
 nerves .
the absence of any of these sensory inputs can influence body sway during static 
 balance .
balance training has been commonly utilized after injury to re - establish basic neural 
 perception to enhance proprioceptive function and kinesthetic awareness3 .
in addition , exercise performed on unstable surfaces rather than 
 under stable conditions seems to more effectively increase muscle activation patterns in the 
 trunk region4 , 5 and limbs6 , while 
 decreasing perceived exertion7 .
the 
 overall effects of this approach , which is termed  core stability and strength enhancement  , 
 may possibly improve athletic performance and reduce the incidence of injury . as a result
, 
 it has a growing popularity not only among elite athletes but also the general 
 population .
for example , training under unstable and imbalanced 
 conditions results in instability that can be experienced during a variety of daily and 
 sport activities8 . however , it is 
 reasonable to assume that using unstable surfaces during training should be based on 
 improvement of the neuromuscular adaptation process , particularly at the early stages of a 
 resistance training program9 .
in addition , 
 it is a favorable to admit that enhancing balance ability produces greater muscular 
 functionality which may maximize athletic performance .
however , only a few studies have been 
 conducted examining the effects of simple balance training in this field .
additionally , it 
 is hard to find a relatively short and time - efficient balance training program , particularly 
 one suitable for middle and high school elite weightlifters .
therefore , the purpose of the present study was to evaluate the effects of 8 weeks of 
 balance training on muscular function equalization that could be utilized in an elite 
 weightlifters ' basic training program .
co , control group ; pre , 
 pre - training ; post , post - training . * , between group significant difference : 
 p<0.05 thirty - two male elite weightlifters were recruited .
the subjects were 16 middle school ( ms ) 
 weightlifters ( control group n=8 , exercise group n=8 , average age 14  years ) with an 
 averageweight lifting experience of 25.44 months , and 16 high school ( hs ) weightlifters 
 ( control group n=8 , exercise group n=8 , average age 17.00  years ) with an average 
 weightlifting experience of 55.44 months .
this study meets the ethical standards of the 
 international journal of sports medicine10 the physical characteristics of the subjects are summarized in 
 table 1 .
anthropometric measurements of all subjects included height ( cm ) , and body weight ( kg ) , and 
 percent body fat ( % ) , was measured by a body composition analyzer ( jawon medical , gyeongsan , 
 korea ) at the exercise physiology laboratory of dong - a university .
basic physical 
 performances were measured by a helmas ( o2 run , seoul , korea ) system before and after the 
 8-week balance - training program and included sit - ups , push - ups , handgrip power , vertical 
 jump , side step , body reaction time , one - leg standing time with closed eyes .
flexibility in 
 the sagittal plane , sit and reach , and back hyperextension in the prone position were also 
 measured .  
photographs of the aspects of the balance training program all subjects were asked to come to the laboratory before 8:00 on the experimental day .
the 
 strength tests were performed using a cybex norm 770 ( cybex division of lumax ,
the maximal voluntary knee flexion and extension % body weight peak 
 torque ( % bwpt ) were assessed for both legs at angular velocities of 60/s and 120/s . 

additionally , upper arm internal and external rotation were measured at angular velocities 
 of 30/s and 90/s . at the end
, wrist extensor and flexor power were also measured at 
 angular velocities of 10/s and 30/s . for each test , each subject performed a maximal 
 contraction three times , with a recovery period of 3 minutes to avoid fatigue induced 
 performance decrements .
the 
 reliability of the strength test was investigated prior to the formal measurement . 

intraclass correlation coefficients for the test - retest reliability ranged from 0.890.99 
 for the knee , arm , and wrist tests .
the 8-week balance training - program was conducted after baseline measurements , as detailed 
 in table 2 and fig .
the measured values of the control groups , and the exercise groups before and after the 
 8-week balance training program were compared using one - way anova .
meanse , co , control group ; pre , pre - training ; post , post - training .
hs ; high school 
 athlete , ms ; middle school athlete , tv ; tidal volume . * ,
, significant pre and post difference : p<0.05 no appreciable changes in body composition were found on completion of the 8-week balance 
 training program ( table 1 ) . in the ms groups , there was a significant difference in the number of push - ups between the 
 control ( co ) , and exercise groups at pre - training ( pre ) and post - training ( post ) while no 
 differences were found in the hs groups and time trials ( p<0.05 ) .
in addition , in the hs 
 groups , there were significant differences in one - leg standing time with closed eyes ( co : 
 14.103.19 vs. pre : 22.123.40 vs. post : 39.756.78 , respectively , p<0.05 ) . in the 
 flexibility measurement , back hyperextension
was significantly increased in the hs group by 
 the training , however no improvements were found in the sit and reach test in any group 
 ( table 3 ) .
meanse ; * : significantly different from pre hs ; # , significantly different form pre 
 ms .
external rotation ( er ) ; internal rotation ( ir ) ; knee extension ( ke ) ; knee flexion 
 ( kf ) .
co , control group ; pre , pre - training ; post , post - training .
hs ; high school 
 athlete , ms ; middle school athlete meanse ; * : significantly different form co ; # , significantly different from pre .
co , 
 control group ; pre , pre - training ; post , post - training .
hs ; high school athlete , ms ; 
 middle school athlete the effects of the 8-week training program on the wrist , arm rotation , knee isokinetic 
 extension , and flexion tests are presented in tables 
 4 and 5 . after training , in the hs 
 exercise group , there was a significant difference in post left - arm external rotation torque 
 from the control group and the pre hs values . in the ms group , after 8 weeks of training , 
 the left - arm , external rotation torque of % bwpt significantly increased ( p<0.05 ) .
, only the hs group showed a significantly positive change in arm 
 internal rotation % bwpt ( left right value ) ; no significantly positive changes were found in 
 the ms group ( p<0.05 , respectively ) .
interestingly , a significantly negative change was 
 found in arm external rotation of the hs group ( p<0.05 ) ( table 5 ) .
inter and intragroup knee extension , flexion of % bwpt 
 remained unchanged , while knee flexion of % bwpt ( left  right ) of post hs was significantly 
 different from that of co of post hs ( p<0.05 ) ( table 
 5 ) .
knee extension % bwpt ( left  right ) of post hs also showed a significant change 
 from the pre hs value .
elite weightlifters should possess equal strength in both arms , because imbalance of 
 muscular strength may hamper their performance , and it may further lead to serious injuries . 
 in the present study , we found severe imbalances in bilateral muscle strengths of ms and hs 
 students .
this study showed that a newly designed 8-week balance - training program 
 beneficially affected elite weightlifters in terms of balanced strength gain .
these changes 
 were more significant among the highly - unbalanced hs elite lifters than among the ms 
 group .
the human body is kept in balance through complicated processes including visual , 
 vestibular , and proprioceptive information11 .
muscle forces coupled with kinematic 
 adjustments , especially around the knee and the ankle joints , are used to maintain stability 
 and prevent falling12 .
furthermore , there 
 is some evidence that reduced lower extremity strength is associated with poor balance and a 
 greater risk of unexpected falls13 , 14 , though this is not always the case15 , 16 .
however , few studies have been 
 conducted which have investigated the effects of simple balance training in this field .
one 
 study showed significant correlations between hockey skating exercise and static balance 
 tests,19 which is in agreement with the 
 findings of present study of increased one - leg standing time with closed eyes .
another study 
 reported an increase in vertical jump height following 5 weeks of balance training20 .
however , the present study did not show 
 any significant leg power improvement . in the present study ,
relatively lower loads were 
 utilized throughout whole exercise program , and the majority of exercises were based on 
 using subjects ' body weight and gym balls .
thus , we recommend dynamic balance training for 
 further performance enhancement . on the other hand ,
some studies have found 
 instability - induced decreases ( 6070% ) in force21 , 
 22 , and other studies reported more 
 modest decrements ( 610% ) in force and power11 or no decrement in force with a dynamic barbell chest press23 .
in addition , a small decrement in 
 muscular force and power may not compromise the training effect .
perhaps the extent of 
 instability is a mitigating factor in the depression of force24 . also , an unstable base such as a swiss ball may permit strength 
 training adaptation if the instability is moderate , allowing the generation of overload 
 forces22 . there is another reason why this study focused more on muscular balance rather than 
 strength and/or power development .
greater instability seems to challenge the neuromuscular 
 system to a greater extent than stable conditions , possibly enhancing strength gains , which 
 are attributed to neural adaptations .
hence , instability resistance training programs may 
 improve athletic performance , while reducing the incidence of injuries .
balance is generally defined as the ability to maintain the body 's center of gravity within 
 its base of support and can be categorized as either static or dynamic balance .
static 
 balance is the ability to sustain the body in static equilibrium or within its base of 
 support1 , 2 .
dynamic balance is believed to be more challenging because it 
 requires the ability to maintain equilibrium during a transition from a dynamic to a static 
 state25 .
the results of the present 
 study demonstrate that upper body back hyperextension , a flexibility factor , significantly 
 increased after the 8-week balance - training program .
this supports the suggestion that 
 balance training for stability maintenance linearly increases antagonist activity .
previous 
 studies have shown that individuals with stronger knee and ankle muscles have superior 
 balance ability28 , 29 .
in addition , reduced strength has been linked with poor balance 
 and a higher risk of falls13 , 14 .
the present study showed the training program tend to 
 balance the strength of the subjects without any strength compromise , especially the hs 
 group .
as mentioned in the introduction , weightlifters must possess strength since it is 
 directly related to their athletic performance .
however , at the end of explosive movement , 
 only absolute muscular balance maintains the weight .
muscular balance without strength loss 
 may be the best strategy for a training program .
weightlifting features a jerk action and 
 left and right balance of strength is easy to change .
present study , high school athletic career , such as a higher middle school 
 athletes is higher than the difference of the left and right balance .
the balance exercise 
 results show that imbalance in the strength of the right and left sides can be reduced .
isokinetic testing is used by many clinicians to assess muscular function such as , power 
 and peak torque .
it is generally used to monitor the progress of rehabilitation from 
 injuries to the rotator cuff muscles , knees and wrists30 . in the present study , arm internal and external rotation of % bwpt 

left - right muscular imbalance in the hs group was 
 significantly reduced after 8 weeks of balance training .
it is difficult to believe the 
 results of this study would extrapolate to the general population .
however , the difference 
 between the balance of strength training for a long period of time expressed through 
 movement was improved , also the public can expect the effect to be considered .
adult when it 
 is advantageous to considered from young players to continue to exercise to keep the left 
 and right balance .
equalized strength gain is critical for the improvement of the athletic performance of 
 elite weightlifters .
however , weightlifters and their coaches tend to focus training only on 
 general strength gain .
the results of this study suggest that the 8-week balance training 
 program adjusts and maintains unbalanced strength , which may enhance performance .
[ purpose ] balance is generally defined as the ability to maintain the body 's center of 
 gravity within its base of support and may be categorized by either static or dynamic 
 balance . 
 the purpose of the present study was to evaluate the effect of 8 weeks of balance 
 training on strength , and the functional balance ability of elite weightlifters . 
 
 [ subjects ] thirty - two elite weightlifters were recruited for the present study . 
 they were 
 divided into exercise groups ( 8 high school students , 8 middle school students ) and 
 control groups ( 8 high school students , 8 middle school students ) . 
 [ methods ] body 
 compositions were measured by the electrical impedance method , and a helmas system was 
 used to measure basic physical capacities . 
 the muscular function test was conducted using 
 a cybex 770 . 
 [ results ] there were no significant changes in body composition after the 
 training . 
 in contrast , significant changes were found in the number of push - ups , one - leg 
 standing time with eyes closed , and upper body back extension . 
 interestingly , only the 
 left arm external rotation value after the exercise training program showed a 
 statistically significant difference from the baseline value . 
 [ conclusion ] the peak torque 
 values of shoulder internal rotation and knee extension were significantly changed 
 compared to the baseline values , which mean subjects showed balance of their muscular 
 power . therefore , the results of the present study suggest that an 8-week balance - training 
 program would positively affect elite weightlifters ' balance ability and flexibility . 
 we 
 think that well - balanced muscular functionality may enhance athletes ' sport 
 performance .