warm - up exercises for postural control are an important factor for normally healthy , 
 ordinary people as well as athletes .
such postural control refers to automatic responses in 
 the vestibular system , vision , and proprioception1 .
dynamic balance is the ability 
 to maintain equilibrium while in motion or to move the body from a static to a dynamic 
 state3 .
fallings are the leading cause of death 
 from injury in elderly people4 . in the 
 athletic population ,
the loss of dynamic balance is an important factor that may cause 
 injury in sport activity5 .
warm - up 
 exercises are light exercises that are conducted prior to strenuous physical activity , which 
 aim to reduce damage , such as strains and sprains , during performance .
they raise 
 intramuscular temperatures , thereby improving muscle flexibility and adaptability , and 
 enhance postural control6 .
warm - up exercises conducted before exercises or sports activities include stretching , 
 treadmill walking , and plyometric exercise6 , 7 . stretching is commonly used as a warm - up 
 exercise to increase people s range of motion and blood flow rates , and prevent 
 injuries8 . muscle strength and 
 flexibility
the body is further able to move more comfortably 
 following stretching , which is also helpful for preventing injuries in all kinds of 
 sports9 .
it enhances aerobic ability , increases muscle performance 
 during exercise , and has a positive effect on balance ability , as well7 , 10 .
it can improve body equilibrium , coordination , 
 agility , and power , and it has recently received considerable attention as a warm - up 
 exercise that enhances physical ability6 , 11 .
plyometric exercises use high - speed 
 eccentric exercises to advance concentric muscle action , reflexive responses , and functional 
 exercise patterns .
it develops lower body muscle strength , muscle control , and dynamic 
 balance12,13,14 . as warm - up exercises , the above
three exercises greatly affect postural stability . however , 
 research into the effects of each exercise on balance is lacking . accordingly , this study 
 aimed to examine how stretching , plyometric , and treadmill exercises influence the dynamic 
 balance necessary for sports activities .
their 
 characteristics are presented in table 
 1table 1.subject characteristics ( n=22)weight ( kg)height ( cm)bmi ( kg / m)male ( n=10)66.9  1.3171.3  0.922.8  0.4female ( n=12)52.6  0.6161.8  0.820.1  1.4 . the purpose of the study was explained to the subjects who signed consent 
 forms to participation in the study .
then , the approval of the ethics committee of the 
 catholic university of pusan was obtained ( cupirb-2014 - 008 ) .
none of the subjects had 
 orthopedic or neurological diseases , dizziness , or problems maintaining balance .
this study 
 utilized biorescue ( rm ingnierie , rodez , france ) to measure the limit of stability ( los ) 
 into the evaluation of the subjects dynamic balance .
the subjects conducted stretching , plyometric exercises , and treadmill walking for set 
 times over a period of three days . the subjects dynamic balance was then measured .
the 
 measurements for each exercise were taken three times : prior to the intervention , 
 immediately after the intervention , and 20 minutes after the intervention .
the subjects conducted stretching of the bilateral 
 quadriceps femoris , hamstrings , gastrocnemius , and soleus .
they extended each muscle for 45 
 seconds before resting for 15 seconds , repeating the same motion twice .
the subjects 
 treadmill walking was set at 1.2 m / s , the normal gait speed of adults in their 20s15 .
the plyometric exercise program was 
 followed by the methods described in previous research14 , 16 . at a metronome speed of 
 100 bpm
, the subjects conducted four motions  the plyometric squat , plyometric lunge , lateral 
 jump , and forward jump  for 45 seconds before resting for 15 seconds .
the subjects repeated 
 the exercises four times . the data were analyzed using spss 21.0 .
repeated measures two - way analysis of variance 
 repeated measure was used to examine the effects of the different kinds of exercise over 
 time ( table 2table 2.comparison of limit of stability before and after intervention for each 
 exercisebefore exerciseafter exerciseafter 20  minstretching14,936.6  3,81615,292.1  4,305.215,833.2  3,977.9plyometric14,948.1  5,275.813,545.9  5,467.815,231.9  5,482.4treadmill15,528.6  4,075.314,568.9  3,962.214,707.3  3,940.8 ) .
there were no 
 statistical differences among the exercises ( f=0.34 , p=0.79 ) and no statistical differences 
 in changes over time ( f=0.33 , p=0.71 ) .
static stretching is generally thought to have a positive effect in since it prevents 
 injuries during a physical activity .
larsen et al.17 reported that there were no changes in their study subjects 
 position sense after quadriceps and hamstring stretching .
the proprioceptors , which engage 
 in position sense , play a crucial role in conducting actions to maintain balance17 .
proprioceptive tissue is thixotropic , and 
 therefore although the proprioceptive sense may be changed by stretching , the stretching 
 need to be conducted for a long time17 . 
 in this study , stretching was carried out for a short time and therefore was not able to 
 change the proprioceptors .
research verifying that treadmill walking improves balance ability has mostly investigated 
 patients with neurological system disorders10 , 18 .
therefore , we considered that treadmill 
 walking had no effect on the subjects of the present study because they were healthy people . 

in contrast with previous study results that showing that a jumping exercise such as 
 plyometric exercise , enhances balance ability , in the present study , the subjects los 
 values , an index of dynamic stability , did not increase .
plyometric exercises use abductor 
 and adductor muscles more than ordinary jumps , and therefore greater loads are imposed by 
 them , triggering the mobilization of additional muscles . unlike a previous study in which a 
 two - minute resting time was given ,
this study provided a resting time of only 30 seconds , 
 and therefore the subjects muscle fatigue were not able to completely recover from fatigue 
 after the exercises19 .
in particular , the hip extensor muscles influence balance 
 in the standing and bending positions .
balance ability decreases as muscle fatigue 
 accumulates and proprioceptive responses to the joints are inhibited21 .
interestingly , we found that balance ability greatly 
 decreased immediately after the plyometric exercises but was swiftly recovered thereafter . 

it is recommended that future research reduce muscle fatigue by extending the resting time 
 and examining the subsequent changes over time .
this study found that warm - up exercises such as plyometric exercises , stretching , and 
 treadmill walking have no effect on the dynamic of balance in healthy subjects .
 [ purpose ] to examine how stretching , plyometric , and treadmill exercises influence the 
 dynamic balance necessary for sports activities . 
 [ subjects and methods ] twenty - two healthy 
 subjects participated in this study . 
 the subjects conducted stretching , plyometric 
 exercises , and treadmill walking for set times over a period of three days . the subjects 
 dynamic balance was then measured . 
 the measurements were taken prior to the intervention , 
 immediately after the intervention , and 20 minutes after the intervention . 
 all the 
 intervention times were set at 16 minutes , excluding resting times . 
 the data were analyzed 
 with using the two - way anova . 
 [ results ] there was no interaction between exercises and 
 time . 
 there were no statistical differences among the exercises and no statistical 
 differences in changes over time . 
 [ conclusion ] this study found that warm - up exercises 
 such as plyometric exercises , stretching , and treadmill walking have no effect on the 
 dynamic of balance in healthy subjects . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION