balance is an essential requirement for the successful performance of an extensive range of 
 human behaviors .
balance efficacy is an individual 's confidence in his / her ability to 
 maintain balance and avoid falling when performing behaviors such as standing on a chair to 
 reach for an object or walking in a cluttered environment1 .
the maintenance of balance depends on the integration of inputs from the somatosensory , 
 visual , and vestibular systems2 .
transcutaneous electrical nerve stimulation ( tens ) is a usefully applied and well - tolerated 
 clinical modality .
although stimulation at a sub - motor threshold amplitude is primarily used 
 for reducing pain , other effects are also well established , and tens at different amplitudes 
 has been shown to affect the excitability of spinal interneurons and motor neurons3 .
cho et al.4 reported that tens improved 
 spasticity and balance of patients with chronic stroke .
guariglia et al.5 noted that the application of tens to the 
 neck muscles on the paretic side of patients with hemispatial neglect improved postural 
 control and spatial orientation .
however , to our knowledge , the relationship between the 
 balance and the application of tens to the lower limbs has not been established . in 
 addition , the effect of tens on the muscles of healthy subjects is not well known . 

therefore , the purpose of the present study was to investigate the effect of tens applied to 
 the skin overlying the bellies of the gastrocnemius muscles of the lower limbs on the 
 balance and plantar pressure of healthy adults .
their average age , 
 height , and weight were 21.36  1.81  years old , 166.65  6.47  cm , and 61.99  11.16  kg , 
 respectively .
those who did not have neurological or musculoskeletal abnormality that 
 affected balance were selected .
the subjects were forbidden to take medicine or drink 
 alcohol in the 24 hours prior to the study .
a sufficient explanation about this study was 
 given and only those who consented to participation were included . in this study , in order to measure balance ability , biodex balance system sd ( biodex inc .
, 
 shirley , ny , usa ) was used for the stability limit test and the fall risk test .
the base of 
 support was connected to a computer running proprietary software ( biodex , ver 0.0 , biodex , 
 inc . ) which computes an objective balance evaluation .
the subjects took off their shoes , stepped on the footplate , folded their arms on the trunk 
 comfortably , and maintained their body in an upright position while staring at the monitor 
 in front of them .
the location of the feet was where the line of gravity that passed through 
 the ankle joint vertically met the marked line on the footplate , and a reference point was 
 marked on the foothold in order to minimize changes in the reference point in the repeat 
 measurement .
the f - scan system consists of an insole sensor that measures plantar pressure , a 
 converter that is attached to the legs , cables that connect the converter to a computer , and 
 software for the analysis of plantar pressure . in this system ,
the thickness of the mat 
 measuring pressure is 0.88  mm , and it has128 resistance sensors of 9  16  mm are arranged in 
 an 8  16 array ; data is sampled at 3,072  hz .
we 
 used three different sizes of pressure mats : 230  100  mm , 250  100  mm , 270  100  mm .
their soles were divided into regions in 
 order to analyze the pressure distribution characteristics of each region rather than 
 obtaining information on pressure on the soles as a single number . in this study ,
the foot 
 was divided into eight different regions for the measurement of pressure6 : two toe regions , three forefoot regions , 
 one midfoot region ( m ) , and two heel regions ( h1 and h2 ) .
the toes were divided into the 
 great toe region ( t1 ) and the second to fifth toe region ( t2 ) . among the three forefoot 
 regions ,
the medial forefoot region was below the first caput metatarsalis ( f1 ) , the middle 
 forefoot region was below the second and the third caput metatarsalis ( f2 ) , and the lateral 
 forefoot region was below the fourth and fifth caput metatarsalis ( f3 ) . the maximum pressure 
 of each region of the foot during the performance of a task was measured .
the signal input 
 was delivered to a computer interface via a 10  m attached to the subjects ' waists .
data were 
 collected and analyzed using f - scan research tam / stam 6.00 software ( tekscan inc . , south 

boston , ma , usa ) . in order to reduce errors at the arch , the subject wore the f - scan mat on their bare feet 
 and walked in a straight line for 10 seconds three times
adhesive transcutaneous electrical nerve stimulation ( tens ) electrodes were attached to the 
 medial and lateral bellies of the gastrocnemius muscle . after the attachment of the 
 electrodes , subjects ' balance ability and plantar pressures were measured as described 
 above .
the independent t - test was 
 conducted in order to compare balance test and plantar pressure results prior to and after 
 the application of tens .
all data was expressed as mean  sd and statistical significance 
 was accepted for values of p<0.05 .
the fall risk test result and the stability test result measures of balance ability were 
 0.77  0.31 and 48.85  14.18 , respectively .
these values increased after the application of 
 the tens , but only the stability limit test showed a statistically significant result 
 ( p<0.05 ) ( table 1 ) . according to the analysis of the maximum plantar pressure , t1 was 1.67  0.81 , t2 was 0.87 
  0.58 , f1 was 3.94  1.77 , f2 was 5.83  2.00 , f3 was 2.32  1.36 , m was 1.93  1.10 , h1 
 was 10.16  4.03 , and h2 was 4.11  3.00
. maximum plantar pressure after the tens 
 application decreased in all regions except for t1 , and the decrease was statistically 
 significant at f2 and f3 ( p<0.05 ) ( table 
 2 ) .
balance control in an upright position is required for independence in activities of daily 
 living ( adl)7 . in addition , the definition 
 of human balance , dynamic postural control to prevent falling8 , implies that balance performance is necessary to avoid falls9 .
the principal objective of this study was to evaluate the effects of tens application to 
 the skin overlying the bellies of the gastrocnemius muscles of the lower limbs on the 
 balance and plantar pressures of healthy adults .
the fall risk test and stability limit test 
 were used to assess balance ability .
our results show that balance scores improved in the 
 fall risk test and stability limit test after the application of tens , and a statistically 
 significant difference was noted in the stability limit test .
citaker et al.10 reported that light 
 touch - pressure , vibration , and two - point discrimination of sensations on the foot sole 
 decreased in mild to moderately disabled patients with multiple sclerosis ( ms ) , and as a 
 result , one - leg standing balance ability decreased .
decrease in the sensitivity of the foot 
 sole is related with imbalance in the ms population .
prennou et al.11 found that tens reduced neglect - related postural 
 instability after stroke , but no effect was observed in patients without neglect .
tens was used in this study with a view to improving the balance of healthy subjects .
tens 
 is a safe and well - established procedure that can be delivered over prolonged periods , via 
 cutaneous electrodes glued to the skin .
this intervention consists of stimulating 
 superficial cutaneous nerve fibers of large diameter12 , by an electric current of relatively short - pulse duration and 
 intensity below the motor threshold13 .
plantar pressure measurement is being increasingly used in both research and clinical 
 practice to compare gait patterns of different clinical groups and to evaluate the effects 
 of footwear , and orthotic and surgical interventions14 . in the present study , the maximum plantar pressures of the different foot regions after the 
 application of tens decreased , except that of t1 , and statistically significant differences 
 were found at f2 and f3 .
walking speed has been shown to linearly influence the loading patterns beneath the hallux 
 and the rearfoot . however ,
medial and middle forefoot loading initially increases at slower walking 
 speeds , but remains constant or decreases as subjects began to walk faster , and this has 
 been attributed to a decrease in contact time as walking speed increases15 .
while changes in loading patterns have 
 been observed at the rearfoot , hallux , and forefoot , the forces beneath the medial and 
 lateral midfoot are not significantly altered by increases in walking speed16 .
our results suggest that tens applied to the skin overlying gastrocnemius muscles improves 
 the balance ability of healthy adults .
although the mechanisms of postural control after the 
 application of tens to the lower limbs in healthy adults are not well known , the results of 
 this study indicate that cutaneous stimulation increases postural stability .
therefore , we 
 can conclude that tens application to the skin overlying the gastrocnemius muscle is a 
 useful strategy that enhances the balance ability of healthy adults .
furthermore , cutaneous 
 stimulation of the lower limbs may help to improve the balance of older people .
   [ purpose ] the purpose of the present study was to investigate the effect of tens applied 
 to the skin overlying the bellies of the gastrocnemius muscles of the lower limbs on 
 balance and plantar pressure of healthy adults . 
 [ subjects and methods ] twenty - eight 
 healthy college students were the subjects of this study . 
 adhesive transcutaneous 
 electrical nerve stimulation ( tens ) electrodes were attached to the medial and lateral 
 belly of the gastrocnemius muscle . before and after the application of the tens , subjects ' 
 balance ability and maximum plantar pressure were measured and compared . [ results ] the 
 scores improved in the balance tests , including the fall risk test and the stability limit 
 test , after the application of tens , and a statistically significant difference 
 was noted 
 in the stability limit test . the maximum plantar pressure after the application of tens 
 decreased except beneath the big toe , and statistically significant difference was found 
 under the forefoot . 
 [ conclusion ] the results of present study suggest that tens applied to 
 the skin overlying gastrocnemius muscles is useful strategy that improves the balance 
 ability of healthy adults . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION