Technology and Health Care 22 (2014) 395–402 DOI 10.3233/THC-140796 IOS Press
395
The effect of transcutaneous electrical nerve stimulation on postural sway on fatigued dorsi-plantar flexor JaeHo Yu, SoYeon Lee, HyongJo Kim, DongKwon Seo, JiHeon Hong and DongYeop Lee∗ Department of Physical Therapy, SunMoon University, Asan, Korea Received 26 October 2013 Accepted 23 January 2014 Abstract. The application of transcutaneous electrical nerve stimulation (TENS) enhances muscle weakness and static balance by muscle fatigue. It was said that TENS affects decrease of the postural sway. On the other hand, the applications of TENS to separate dorsi-plantar flexor and the comparison with and without visual input have not been studied. Thus, the aim of this study was to compare the effects of TENS on fatigued dorsi-plantar flexor with and without visual input. 13 healthy adult males and 12 females were recruited and agreed to participate as the subject (mean age 20.5 ± 1.4, total 25) in this study after a preliminary research. This experiment was a single group repeated measurements design in three days. The first day, after exercise-induced fatigue, the standing position was maintained for 30 minutes and then the postural sway was measured on eyes open(EO) and eyes closed(EC). The second, TENS was applied to dorsi flexor in standing position for 30 minutes after conducting exercise-induced fatigue. On the last day, plantar flexor applied by TENS was measured to the postural sway on EO and EC after same exercise-induced fatigue. The visual input was not statistically difference between the groups. However, when compared of dorsi-plantar flexor after applied to TENS without visual input, the postural sway of plantar flexor was lower than the dorsi flexor (p < 0.05). As the result, the application of TENS in GCM clinically decreases the postural sway with visual input it helps to stable posture control and prevent to falling down. Keywords: Transcutaneous electrical nerve stimulation(TENS), postural sway, visual input, fatigue, dorsi flexor, plantar flexor
1. Introduction The postural control refers the capability to respond the postural sway caused by any external impact during a static state of dynamic motion and is defined as the capability to maintain the center of mass of whole body within the support base [1]. The human postural control employs various sensories from visual, vestibular and somathetic sensory systems [2–4]. Among those sensories, the visual sensory is reported to reduce the postural sway by limiting external elements for fall [5]. Vuillerme et al. reports, for young adults, bending fatigues on the foot top and sole caused by isokinetic movement increase posture sways in a great deal [6]. Previous studies have reported that thigh muscles with high fatigue are harder for the postural control than normal thigh muscles [7]. The plantar flexor and the dorsiflexor are reported for interaction to each other as agonist and antagonist in reducing the postural sway being ∗ Corresponding author: DongYeop Lee, Department of Physical Therapy, SunMoon University, Asan, Korea. E-mail: leedy@ sunmoon.ac.kr.
c 2014 – IOS Press and the authors. All rights reserved 0928-7329/14/$27.50
396
J. Yu et al. / The effect of transcutaneous electrical nerve stimulation on postural sway
effective in stabilizing the posture as muscles used to maintain the posture [8]. The muscular fatigue is reported to increase the posture imbalance and reduce the strength eventually causing the postural sway and velocity [9–11]. Also, the change of somatic sensory input due to the muscular fatigue is reported to be possible causing defects on the neural muscles and the postural control [7]. Also, in previous studies, the relation between the fatigue and the changed neural muscle control is explained; muscles changed by the muscle fatigue send input signals in reduced transmission rate so that the reduced output signals influence to the capability to form effective actions [12]. Other studies report that if a muscle treatment is performed to fatigue occurred quadriceps and hamstring of healthy adults, the respond time of muscles can be controlled [13]. In Gimmon et al., it is reported that the increase of postal sway due to muscle fatigues is a result of the functional posture instability and may result the reduction of postural control [7]. On the other hands, the application TENS improves the postural instability and recovers the muscle power reduction occurred by muscle fatigues [14]. TENS is defined first by American Physical Therapy Association as applying electrical stimulation to control pain [15]. Yoon et al. states in his work that the electrical stimulation is designed to apply artificial external electricity to biological tissues and used for various purposes including the recovery and retraining of denervated muscles, the reinforcement of weakened muscles and the control of muscle spasm [16]. TENS, one of therapeutic electrical stimulations is known to reduce the intermittent ankle clonus and rigidity and improve the walking function [17,18]. Several studies report that the application of TENS shows tremendous effects on the muscle strength and the movement of lower limbs [19–21]. Also, in researches performed to health adults, TENS applied to lower limbs has an immediate effect on the postural control [17,22]. Also, it is reported that TENS on knees during standing position reduce the postural sway [23]. However, recent several studies show that no difference is detected on the neutral muscle respond after TENS application [24,25]. As above, although various studies on TENS have been conducted, researches either on result comparisons and analyses by separating the dorsiflexor and the platarflexor that are tremendously influential to walking with roles of agonist and antagonist or differences caused by existing or non-existing visual inputs are insufficient. Especially, prior studies have applied only TENS on thigh muscles and almost no study have compared by applying it to other lower limb muscles. Therefore, this study aims to find the difference of postural sway according to existence and none-existence of visual input when TENS is applied to the dorsiflexor and the plantarflexor.
2. Method 2.1. Subjects The subjects are selected from adult males and females in healthy physical conditions who agree to participate after the advance survey. The number of participants are total 25 persons including 13 males (average age 21 ± 1.8) and 12 females (average age 20 ± 0.6). The physical characteristics of participants are as Table 1. Exclusion criteria are ones having any damage in the physical balance due to any musculoskeletal operation or damage or any visual or auditory loss. And no participant is excluded because of such cause. However, two participants who have had a personal cause or experienced a defect in the balance are dropped from the study because of the repeated disturbance in the measurement.
J. Yu et al. / The effect of transcutaneous electrical nerve stimulation on postural sway
Gender Age (yrs) Height (cm) Weight (kg)
(a)
397
Table 1 General characteristics Female (n = 12) Male (n = 13) 20.00 ± 0.60 21.00 ± 1.80 161.40 ± 5.80 174.50 ± 3.90 54.40 ± 7.70 69.50 ± 11.00
(b)
Fig. 1. Exercise induced fatigue (a) dorsiflexion, (b) platarflexion. (Colours are visible in the online version of the article; http: //dx.doi.org/10.3233/THC-140796)
2.2. Materials and methods In the experimentation, measurements are performed to one group for total three days. On the first day, the participants are collected and measurements of their heights and weights using the body composition analyzer (Inbody 570, Biospace, Korea) and postural sways using TETRAX (Sunlight Co. Ltd, Israel) are performed. Later, to cause fatigues on their legs, bending movements of foot top and foot sole are performed. The maximum height of foot sole bending is set to the point to which the participants can lift in maximum while the limit for the foot top is set to the point right before completely touching on the floor. Such movements are performed under the supervision of research staff. Fatigue causing movements for total 10 seconds including the 7 second bending of the foot top Fig. 1(A) and the 3 second bending of the foot sole Fig. 1(B) are performed for total 40 times [7]. The fatigue causing movements are conducted as the participants standing on toes on the plywood (45 cm × 45 cm) of 4 cm height having feet spread to the shoulder width while they take off shoes and socks to perform more accurate movement. On the first day, the participants maintain the standing posture for 30 minute after completing the fatigue causing movements without any treatment and the postural sway is measured. First, the measurement is made having eyes opened (EO) for 32 seconds and later, the measurement is made having eyes closed (EC). After the experiment of the first day, one day resting is given to avoid any influence to the next experiment. On the second day, after performing fatigue causing movements as above, TENS (STT-500, Stratek, Korea) is applied with the frequency of 100 Hz and 8.4 mA on the tibialis anterior for 30 minutes during standing [14]. After the application of TENS, using TETRAX, the postural control is measured. On the third day, the final day of experimentation, after performing fatigue causing movements during the same time period, TENS with the same frequency and the intensity is applied to the gastrocnemius and the postural sway is measured.
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J. Yu et al. / The effect of transcutaneous electrical nerve stimulation on postural sway
(a)
(b)
Fig. 2. Attached point of pad (a) tibialis anterior, (b) gastrocnemius. (Colours are visible in the online version of the article; http://dx.doi.org/10.3233/THC-140796)
For TENS, the equipment is used and pads are attached on the tibialis anterior, the representative muscle for the foot top bending at the muscle’s 1/3 and 2/3 points from the top Fig. 2(A) and on the gastrocnemius selected from muscles for the foot sole bending considering the muscle size. On the gastrocnemius, as shown in Fig. 2(B), two pads are attached on each of medial and lateral branches 1/4 and 3/4 points from the top of the muscle. TETRAX is composed of the platform to measure the postural sway and the main computer Fig. 3. And the postural sway is measured by using the pressure applied to the foot stand on the stillness of foot during standing and the dynamic movement. The platform is defined as the left heel (A) and toe (B) and the right heel (A) and toe (B) as Fig. 4. And measurements are made by segmenting as the left foot anterior to posterior postural sway (AB), the right foot anterior to posterior postural sway (CD), the posterior medial to lateral postural sway (AC) and the anterior medial to lateral postural sway (BD). The foot stand converts the distance away from the center area to the amplitude, and the amplitude is converted to the frequency showing the correlation coefficient between the two food stands. And the value converted to index is measured. To reduce the sensitivity, participants are measured without wearing any shoe or sock while the auditory stimulation is blocked by using ear covers. 2.3. Data analysis All measurement values are statistically processed by using SPSS 12.0 program for Windows. According to existence or non-existence of the visual input, the reference value and TENS are applied to the foot top bending muscle and the foot sole bending muscle during the standing posture and the difference between measurement values are compared. One Way Repeated ANOVA is used for the analysis method and Bonferroni method is employed as the post-hoc test for the difference on each variable. The significance levels of all statistic analyses are set as p < 0.05. 3. Results Table 2 shows the results after exercise-induced fatigue in standing position and TENS application to dorsi-plantar flexor. As the result, the visual input was not statistically difference between the groups.
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Table 2 The difference of between intervention according to eye open and close
EC
EO
∗
AB CD AC BD AB CD AC BD
TENS application of plantarflexor −642.46 ± 74.52 −816.56 ± 45.07 342.23 ± 86.95 718.24 ± 48.77 −579.05 ± 97.57 −797.28 ± 25.30 328.35 ± 106.29 629.46 ± 60.40
TENS application of dorsiflexor −766.79 ± 48.19 −861.33 ± 21.02 602.14 ± 59.80 733.75 ± 48.19 −685.08 ± 73.07 −739.65 ± 61.26 424.23 ± 81.03 676.80 ± 49.61
No treatment
F
−753.24 ± 52.91 −824.16 ± 22.07 534.70 ± 64.65 777.57 ± 25.94 −701.72 ± 74.59 −772.88 ± 38.94 379.05 ± 86.38 608.21 ± 54.81
1.404 0.584 3.123∗ 0.713 0.594 0.563 0.651 0.496
p < 0.05, mean ± standard deviation, EC: eye close, EO: eye close, TENS: transcutaneous electrical nerve stimulation.
Fig. 3. TETRAX. (Colours are visible in the online version of the article; http://dx.doi.org/10.3233/THC-140796)
Fig. 4. Platform of TETRAX. (Colours are visible in the online version of the article; http://dx.doi.org/10.3233/THC-140796)
However, when compared of dorsi-plantar flexor after applied to TENS without visual input, the postural sway of plantar flexor was lower than the dorsi flexor (p < 0.05). Moreover, according to the post-hoc comparison result, plantar flexor sway (342.23 ± 86.95) is significant lower compared to the dorsi flexor sway (602.14 ± 59.80) (p < 0.05) Fig. 5. 4. Discussion Among various researches using TENS found in many previous studies, Cho et al.’s study reports that TENS application on the gastrocnemius is eventually found to be effective when the difference is analyzed by using the 3D motion analyzer between the before and the after of fatigue occurrence on a normal person by applying a electrical nerve stimulation on the gastrocnemius [14]. Cho et al.’s research is different from the research of this study by applying TENS only on the gastrocnemius while the tibialis anterior is missed, yet, is meaningful for finding the effect of TENS application on the gastrocnemius. Moreover, Cho et al. conducts the research on the recovery of excessive tension with 42 chronic brain
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Fig. 5. The result of post-hoc test on the difference of between intervention. (Colours are visible in the online version of the article; http://dx.doi.org/10.3233/THC-140796)
stoke patients after 6 months or more from stoke occurrences and reports that when TENS is applied on the gastrocnemius, the group of TENS application shows the reduction of postural sway. Therefore, the study states that the application of TENS is helpful to recover the tensed status of muscle [17]. However, according to Yoon et al.’s research, the result of fatigue occurring movement of the quadriceps performed by separating subjects into the functional massage, the stretching and TENS groups shows no significant difference among the groups [16]. As above, previous researches have been attempted to investigate that the application of TENS on fatigue occurred muscle reduces the muscle fatigue. However, the effect is still controversial so that this research is started. Many previous researches that support the reason for selecting the tibialis anterior in dorsiflexor in this experiment have been conducted. Ebig et al. has conducted the plantarflexion to perform the fatigue occurring movements on the peroneal muscle and the tibialis anterior to healthy adult subjects and reported finding no significant difference from the checking the postural sway after the movements [26]. Also, in the research of Tilp et al., the concentric and eccentric contraction performed on the tibialis anterior to compare changes of the length of aponeurosis has been reported to show no significant difference between groups [27]. The reasons that TENS applied on the tibialis anterior and the gastrocnemius is more effective on the gastrocnemius for reducing the postural sway are; first, more motor nerve cells and more movement units ruling muscle tissues are included as the size of muscle is larger [28]. In other words, the gastrocnemius has larger muscle size compared to the tibialis anterior so that the range of electric stimulation is larger for TENS application. Therefore, the application of TENS on the gastrocnemius having larger muscle size than the tibialis anterior is considered to be more effective to the reduction of postural sway. Second, the main supporting muscle when a person is standing for a long time is reported to be the plantarflexor [29]. Also, the plantarflexor includes the soleus muscle and the gastrocnemius and is reported to control the body by being active first when the straight posture is maintained [8]. Therefore, the gastrocnemius belongs to the plantarflexor is considered to be more effective for the postural control than the tibialis anterior, a dorsiflexor. Finally, to support the reason that the distribution rate of AC referring the side unrest of back side is shown to be low as found in this research, Duysens et al. describes that the gastrocnemius is separated by the medial and the lateral fibers and may be moved to sides by the vector
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value starting on the elbow [30]. For example, when the internal branch shrinks strongly, the internal spread of elbow bones may occur and when the side branch shrinks strongly, the external spread may occur. Therefore, this study, based on such mechanism, proves that the application on fatigue occurred gastrocnemius reduces the body’s side unrest by recovering the muscle fatigue. However, when applied to patients having slow feet symptoms due to brain injuries, other results regarding the postural control are considered to be occurred. Therefore if TENS is clinically applied to brain injury patients on the fatigue occurred gastrocnemius after the walking training, it is expected to be helpful to improve the postural control due to reduced muscle fatigue. Also, as the tense is released, the fall is considered to be prevented with stabilized postural control during walking. And various measures to reduce the postural sway and continuous researches is required in the future.
5. Conclusion The purpose of this study is to find the difference impacting on the postural sway depending on the visual input’s existence when TENS is applied to the dorsiflexor and the plantarflexor after fatigue occurring movements. As conclusion, when TENS is applied on the foot top and the plantarflexor for a normal person while the visual information is blocked, the effect is shown only on the plantarflexor. Therefore the clinical application of TENS on the peroneal muscle is effective on the postural control and is considered to be helpful to prevent fall by improving stabilized postural control with the visual input.
References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]
Horak FB, Shupert CL, Mirka A. Components of postural dyscontrol in the elderly: A review. Neurobiol Aging. 1989; 10(6):727-38. Collins JJ, De Luca CJ. The effects of visual input on open-loop and closed-loop postural control mechanisms. Exp Brain Res. 1995;103(1):151-63. Gurfinkel VS, Ivanenko YuP, Levik YuS, Babakova IA. Kinesthetic reference for human orthograde posture. Neuroscience. 1995;68(1):229-43. Kavounoudias A, Gilhodes JC, Roll R, Roll JP. From balance regulation to body orientation: two goals for muscle proprioceptive information processing? Exp Brain Res. 1999;124(1):80-8. Vouriot A, Gauchard GC, Chau N, Benamghar L, Lepori ML, Mur JM, et al. Sensorial organisation favouring higher visual contribution is a risk factor of falls in an occupational setting. Neurosci Res. 2004;8(3):239-47. Vuillerme N, Danion F, Forestier N, Nougier V. Postural sway under muscle vibration and muscle fatigue in humans. Neurosci Lett. 2002;333(2):131-5. Gimmon Y, Riemer R, Oddsson L, Melzer I. The effect of plantar flexor muscle fatigue on postural control. J Electromyogr Kinesiol. 2011;21(6):922-8. Di Giulio I, Maganaris CN, Baltzopoulos V, Loram ID. The proprioceptive and agonist roles of gastrocnemius, soleus and tibialis anterior muscles in maintaining human upright posture. J Physiol. 2009;587(10):2399-416. Gribble PA, Hertel J. Effect of hip and ankle muscle fatigue on unipedal postural control. J Electromyogr Kinesiol. 2004;14(6):641-6. Nam HS, Park DS, Kim DH, Kang HJ, Lee DH, Lee SH, et al. The relationship between muscle fatigue and balance in the elderly. Ann Rehabil Med. 2013;37(3):389-95. Yaggie JA, McGregor SJ. Effects of isokinetic ankle fatigue on the maintenance of balance and postural limits. Arch Phys Med Rehabil. 2002;83(2):224-8. Bellew JW, Fenter PC. Control of balance differs after knee or ankle fatigue in older women. Arch Phys Med Rehabil. 2006;87(11):1486-9. Wojtys EM, Wylie BB, Huston LJ. The effects of muscle fatigue on neuromuscular function and anterior tibial translation in healthy knees. Am J Sports Med. 1996;24(5):615-21.
402 [14]
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Cho HY, Lee SH, In TS, Lee KJ, Song CH. Effect of transcutaneous electrical nerve stimulation(TENS) on changes in postural balance and muscle contraction following muscle fatigue. Journal of Physical Therapy Science. 2011;23(6):899903. [15] Sluka KA, Walsh D. Transcutaneous electrical nerve stimulation: Basic science mechanisms and clinical effectiveness. J Pain. 2003;4(3):109-21. [16] Yoon JG, Ryu JJ, Roh HW, Yang HA, Lee SB. Effect of transcutaneous electrical nerve stimulation(TENS), self stretching and functional massage on the muscule fatigue by maximum muscular strength. J Int Acad Phys Ther Res. 2012;3(2):422-8. [17] Cho HY, In TS, Cho KH, Song CH. A single trial transcutaneous electrical nerve stimulation(TENS) Improves spasticitiy and balance in patients with chronic stroke. Tohoku J Exp Med. 2013;229(3):187-93. [18] Ping Ho, Chung B, Kam Kwan Cheng B. Immediate effect of transcutaneous electrical nerve stimulation on spasticity in patients with spinal cord injury. Clin Rehabil. 2010;24(3):202-10. [19] Ng SS, Hui-Chan CW. Does the use of TENS increase the effectiveness of exercise for improving walking after stroke? A randomized controlled clinical trial. Clin Rehabil. 2009; 23(12):1093-103. [20] Ng SS, Hui-Chan CW. Transcutaneous electrical nerve stimulation combind with task-related training improves lower limb functions in subjects with chronic stroke. Stroke. 2007; 38(11):2953-9. [21] Tyson SF, Sadeghi-Demneh E, Nester CJ. The effects of transcutaneous electrical nerve stimulation on strength, proprioception, balance and mobility in people with stroke: a randomized controlled cross-over trial. Clin Rehabil. 2013; 27(9):785-91. [22] Dickstein R, Laufer Y, Katz M. TENS to the posterior aspect of the legs decreases postural sway during stance. Neurosci Lett. 2006;393(1):51-5. [23] Laufer Y, Dickstein R. TENS to the lateral aspect of the knees during stance attenuates postural sway in young adults. Scientific World Journal. 2007;26(7):1904-11. [24] Armutlu K, Meric A, Kirdi N, Yakut E, Karabudak R. The effect of transcutaneous electrical nerve stimulation on spasticity in multiple sclerosis patients: A pilot study. Neurorehabil Neural Repair. 2003;17(2):79-82. [25] Miller L, Mattison P, Paul L, Wood L. The effects of transcutaneous electrical nerve stimulation (TENS) on spasticity in multiple sclerosis. Mult Scler. 2007;13(4):527-33. [26] Ebig M, Lephart SM, Burdett RG, Miller MC, Pincivero DM. The effect of sudden inversion stress on EMG activity of the peroneal and tibialis anterior muscles in the chronically unstable ankle. Orthopaedic J Orthop Sports Phys Ther. 1997;26(2):73-7. [27] Tilp M, Steib S, Herzog W. Length changes of human tibialis anterior central aponeurosis during passive movements and isometric, concentric, and eccentric contractions. Eur J Appl Physiol. 2012;112(4):1485-94. [28] Choi YM, Kim BC. Muscle fiber characteristics, myofibrillar protein isoforms, and meat quality. Livestock Science. 2009;122(2):105-18. [29] Borg F, Finell M, Hakala I, Herrala M. Analyzing gastrocnemius EMG-activity and sway data from quiet and perturbed standing. J Electromyogr Kinesiol. 2007;17(5):622-34. [30] Duysens J, van Wezel BM, Prokop T, Berger W. Medial gastrocnemius is more activated than lateral gastrocnemius in sural nerve induced reflexes during human gait. Brain Res. 1996;727(1-2):230-32.
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395
The effect of transcutaneous electrical nerve stimulation on postural sway on fatigued dorsi-plantar flexor JaeHo Yu, SoYeon Lee, HyongJo Kim, DongKwon Seo, JiHeon Hong and DongYeop Lee∗ Department of Physical Therapy, SunMoon University, Asan, Korea Received 26 October 2013 Accepted 23 January 2014 Abstract. The application of transcutaneous electrical nerve stimulation (TENS) enhances muscle weakness and static balance by muscle fatigue. It was said that TENS affects decrease of the postural sway. On the other hand, the applications of TENS to separate dorsi-plantar flexor and the comparison with and without visual input have not been studied. Thus, the aim of this study was to compare the effects of TENS on fatigued dorsi-plantar flexor with and without visual input. 13 healthy adult males and 12 females were recruited and agreed to participate as the subject (mean age 20.5 ± 1.4, total 25) in this study after a preliminary research. This experiment was a single group repeated measurements design in three days. The first day, after exercise-induced fatigue, the standing position was maintained for 30 minutes and then the postural sway was measured on eyes open(EO) and eyes closed(EC). The second, TENS was applied to dorsi flexor in standing position for 30 minutes after conducting exercise-induced fatigue. On the last day, plantar flexor applied by TENS was measured to the postural sway on EO and EC after same exercise-induced fatigue. The visual input was not statistically difference between the groups. However, when compared of dorsi-plantar flexor after applied to TENS without visual input, the postural sway of plantar flexor was lower than the dorsi flexor (p < 0.05). As the result, the application of TENS in GCM clinically decreases the postural sway with visual input it helps to stable posture control and prevent to falling down. Keywords: Transcutaneous electrical nerve stimulation(TENS), postural sway, visual input, fatigue, dorsi flexor, plantar flexor
1. Introduction The postural control refers the capability to respond the postural sway caused by any external impact during a static state of dynamic motion and is defined as the capability to maintain the center of mass of whole body within the support base [1]. The human postural control employs various sensories from visual, vestibular and somathetic sensory systems [2–4]. Among those sensories, the visual sensory is reported to reduce the postural sway by limiting external elements for fall [5]. Vuillerme et al. reports, for young adults, bending fatigues on the foot top and sole caused by isokinetic movement increase posture sways in a great deal [6]. Previous studies have reported that thigh muscles with high fatigue are harder for the postural control than normal thigh muscles [7]. The plantar flexor and the dorsiflexor are reported for interaction to each other as agonist and antagonist in reducing the postural sway being ∗ Corresponding author: DongYeop Lee, Department of Physical Therapy, SunMoon University, Asan, Korea. E-mail: leedy@ sunmoon.ac.kr.
c 2014 – IOS Press and the authors. All rights reserved 0928-7329/14/$27.50
396
J. Yu et al. / The effect of transcutaneous electrical nerve stimulation on postural sway
effective in stabilizing the posture as muscles used to maintain the posture [8]. The muscular fatigue is reported to increase the posture imbalance and reduce the strength eventually causing the postural sway and velocity [9–11]. Also, the change of somatic sensory input due to the muscular fatigue is reported to be possible causing defects on the neural muscles and the postural control [7]. Also, in previous studies, the relation between the fatigue and the changed neural muscle control is explained; muscles changed by the muscle fatigue send input signals in reduced transmission rate so that the reduced output signals influence to the capability to form effective actions [12]. Other studies report that if a muscle treatment is performed to fatigue occurred quadriceps and hamstring of healthy adults, the respond time of muscles can be controlled [13]. In Gimmon et al., it is reported that the increase of postal sway due to muscle fatigues is a result of the functional posture instability and may result the reduction of postural control [7]. On the other hands, the application TENS improves the postural instability and recovers the muscle power reduction occurred by muscle fatigues [14]. TENS is defined first by American Physical Therapy Association as applying electrical stimulation to control pain [15]. Yoon et al. states in his work that the electrical stimulation is designed to apply artificial external electricity to biological tissues and used for various purposes including the recovery and retraining of denervated muscles, the reinforcement of weakened muscles and the control of muscle spasm [16]. TENS, one of therapeutic electrical stimulations is known to reduce the intermittent ankle clonus and rigidity and improve the walking function [17,18]. Several studies report that the application of TENS shows tremendous effects on the muscle strength and the movement of lower limbs [19–21]. Also, in researches performed to health adults, TENS applied to lower limbs has an immediate effect on the postural control [17,22]. Also, it is reported that TENS on knees during standing position reduce the postural sway [23]. However, recent several studies show that no difference is detected on the neutral muscle respond after TENS application [24,25]. As above, although various studies on TENS have been conducted, researches either on result comparisons and analyses by separating the dorsiflexor and the platarflexor that are tremendously influential to walking with roles of agonist and antagonist or differences caused by existing or non-existing visual inputs are insufficient. Especially, prior studies have applied only TENS on thigh muscles and almost no study have compared by applying it to other lower limb muscles. Therefore, this study aims to find the difference of postural sway according to existence and none-existence of visual input when TENS is applied to the dorsiflexor and the plantarflexor.
2. Method 2.1. Subjects The subjects are selected from adult males and females in healthy physical conditions who agree to participate after the advance survey. The number of participants are total 25 persons including 13 males (average age 21 ± 1.8) and 12 females (average age 20 ± 0.6). The physical characteristics of participants are as Table 1. Exclusion criteria are ones having any damage in the physical balance due to any musculoskeletal operation or damage or any visual or auditory loss. And no participant is excluded because of such cause. However, two participants who have had a personal cause or experienced a defect in the balance are dropped from the study because of the repeated disturbance in the measurement.
J. Yu et al. / The effect of transcutaneous electrical nerve stimulation on postural sway
Gender Age (yrs) Height (cm) Weight (kg)
(a)
397
Table 1 General characteristics Female (n = 12) Male (n = 13) 20.00 ± 0.60 21.00 ± 1.80 161.40 ± 5.80 174.50 ± 3.90 54.40 ± 7.70 69.50 ± 11.00
(b)
Fig. 1. Exercise induced fatigue (a) dorsiflexion, (b) platarflexion. (Colours are visible in the online version of the article; http: //dx.doi.org/10.3233/THC-140796)
2.2. Materials and methods In the experimentation, measurements are performed to one group for total three days. On the first day, the participants are collected and measurements of their heights and weights using the body composition analyzer (Inbody 570, Biospace, Korea) and postural sways using TETRAX (Sunlight Co. Ltd, Israel) are performed. Later, to cause fatigues on their legs, bending movements of foot top and foot sole are performed. The maximum height of foot sole bending is set to the point to which the participants can lift in maximum while the limit for the foot top is set to the point right before completely touching on the floor. Such movements are performed under the supervision of research staff. Fatigue causing movements for total 10 seconds including the 7 second bending of the foot top Fig. 1(A) and the 3 second bending of the foot sole Fig. 1(B) are performed for total 40 times [7]. The fatigue causing movements are conducted as the participants standing on toes on the plywood (45 cm × 45 cm) of 4 cm height having feet spread to the shoulder width while they take off shoes and socks to perform more accurate movement. On the first day, the participants maintain the standing posture for 30 minute after completing the fatigue causing movements without any treatment and the postural sway is measured. First, the measurement is made having eyes opened (EO) for 32 seconds and later, the measurement is made having eyes closed (EC). After the experiment of the first day, one day resting is given to avoid any influence to the next experiment. On the second day, after performing fatigue causing movements as above, TENS (STT-500, Stratek, Korea) is applied with the frequency of 100 Hz and 8.4 mA on the tibialis anterior for 30 minutes during standing [14]. After the application of TENS, using TETRAX, the postural control is measured. On the third day, the final day of experimentation, after performing fatigue causing movements during the same time period, TENS with the same frequency and the intensity is applied to the gastrocnemius and the postural sway is measured.
398
J. Yu et al. / The effect of transcutaneous electrical nerve stimulation on postural sway
(a)
(b)
Fig. 2. Attached point of pad (a) tibialis anterior, (b) gastrocnemius. (Colours are visible in the online version of the article; http://dx.doi.org/10.3233/THC-140796)
For TENS, the equipment is used and pads are attached on the tibialis anterior, the representative muscle for the foot top bending at the muscle’s 1/3 and 2/3 points from the top Fig. 2(A) and on the gastrocnemius selected from muscles for the foot sole bending considering the muscle size. On the gastrocnemius, as shown in Fig. 2(B), two pads are attached on each of medial and lateral branches 1/4 and 3/4 points from the top of the muscle. TETRAX is composed of the platform to measure the postural sway and the main computer Fig. 3. And the postural sway is measured by using the pressure applied to the foot stand on the stillness of foot during standing and the dynamic movement. The platform is defined as the left heel (A) and toe (B) and the right heel (A) and toe (B) as Fig. 4. And measurements are made by segmenting as the left foot anterior to posterior postural sway (AB), the right foot anterior to posterior postural sway (CD), the posterior medial to lateral postural sway (AC) and the anterior medial to lateral postural sway (BD). The foot stand converts the distance away from the center area to the amplitude, and the amplitude is converted to the frequency showing the correlation coefficient between the two food stands. And the value converted to index is measured. To reduce the sensitivity, participants are measured without wearing any shoe or sock while the auditory stimulation is blocked by using ear covers. 2.3. Data analysis All measurement values are statistically processed by using SPSS 12.0 program for Windows. According to existence or non-existence of the visual input, the reference value and TENS are applied to the foot top bending muscle and the foot sole bending muscle during the standing posture and the difference between measurement values are compared. One Way Repeated ANOVA is used for the analysis method and Bonferroni method is employed as the post-hoc test for the difference on each variable. The significance levels of all statistic analyses are set as p < 0.05. 3. Results Table 2 shows the results after exercise-induced fatigue in standing position and TENS application to dorsi-plantar flexor. As the result, the visual input was not statistically difference between the groups.
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Table 2 The difference of between intervention according to eye open and close
EC
EO
∗
AB CD AC BD AB CD AC BD
TENS application of plantarflexor −642.46 ± 74.52 −816.56 ± 45.07 342.23 ± 86.95 718.24 ± 48.77 −579.05 ± 97.57 −797.28 ± 25.30 328.35 ± 106.29 629.46 ± 60.40
TENS application of dorsiflexor −766.79 ± 48.19 −861.33 ± 21.02 602.14 ± 59.80 733.75 ± 48.19 −685.08 ± 73.07 −739.65 ± 61.26 424.23 ± 81.03 676.80 ± 49.61
No treatment
F
−753.24 ± 52.91 −824.16 ± 22.07 534.70 ± 64.65 777.57 ± 25.94 −701.72 ± 74.59 −772.88 ± 38.94 379.05 ± 86.38 608.21 ± 54.81
1.404 0.584 3.123∗ 0.713 0.594 0.563 0.651 0.496
p < 0.05, mean ± standard deviation, EC: eye close, EO: eye close, TENS: transcutaneous electrical nerve stimulation.
Fig. 3. TETRAX. (Colours are visible in the online version of the article; http://dx.doi.org/10.3233/THC-140796)
Fig. 4. Platform of TETRAX. (Colours are visible in the online version of the article; http://dx.doi.org/10.3233/THC-140796)
However, when compared of dorsi-plantar flexor after applied to TENS without visual input, the postural sway of plantar flexor was lower than the dorsi flexor (p < 0.05). Moreover, according to the post-hoc comparison result, plantar flexor sway (342.23 ± 86.95) is significant lower compared to the dorsi flexor sway (602.14 ± 59.80) (p < 0.05) Fig. 5. 4. Discussion Among various researches using TENS found in many previous studies, Cho et al.’s study reports that TENS application on the gastrocnemius is eventually found to be effective when the difference is analyzed by using the 3D motion analyzer between the before and the after of fatigue occurrence on a normal person by applying a electrical nerve stimulation on the gastrocnemius [14]. Cho et al.’s research is different from the research of this study by applying TENS only on the gastrocnemius while the tibialis anterior is missed, yet, is meaningful for finding the effect of TENS application on the gastrocnemius. Moreover, Cho et al. conducts the research on the recovery of excessive tension with 42 chronic brain
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Fig. 5. The result of post-hoc test on the difference of between intervention. (Colours are visible in the online version of the article; http://dx.doi.org/10.3233/THC-140796)
stoke patients after 6 months or more from stoke occurrences and reports that when TENS is applied on the gastrocnemius, the group of TENS application shows the reduction of postural sway. Therefore, the study states that the application of TENS is helpful to recover the tensed status of muscle [17]. However, according to Yoon et al.’s research, the result of fatigue occurring movement of the quadriceps performed by separating subjects into the functional massage, the stretching and TENS groups shows no significant difference among the groups [16]. As above, previous researches have been attempted to investigate that the application of TENS on fatigue occurred muscle reduces the muscle fatigue. However, the effect is still controversial so that this research is started. Many previous researches that support the reason for selecting the tibialis anterior in dorsiflexor in this experiment have been conducted. Ebig et al. has conducted the plantarflexion to perform the fatigue occurring movements on the peroneal muscle and the tibialis anterior to healthy adult subjects and reported finding no significant difference from the checking the postural sway after the movements [26]. Also, in the research of Tilp et al., the concentric and eccentric contraction performed on the tibialis anterior to compare changes of the length of aponeurosis has been reported to show no significant difference between groups [27]. The reasons that TENS applied on the tibialis anterior and the gastrocnemius is more effective on the gastrocnemius for reducing the postural sway are; first, more motor nerve cells and more movement units ruling muscle tissues are included as the size of muscle is larger [28]. In other words, the gastrocnemius has larger muscle size compared to the tibialis anterior so that the range of electric stimulation is larger for TENS application. Therefore, the application of TENS on the gastrocnemius having larger muscle size than the tibialis anterior is considered to be more effective to the reduction of postural sway. Second, the main supporting muscle when a person is standing for a long time is reported to be the plantarflexor [29]. Also, the plantarflexor includes the soleus muscle and the gastrocnemius and is reported to control the body by being active first when the straight posture is maintained [8]. Therefore, the gastrocnemius belongs to the plantarflexor is considered to be more effective for the postural control than the tibialis anterior, a dorsiflexor. Finally, to support the reason that the distribution rate of AC referring the side unrest of back side is shown to be low as found in this research, Duysens et al. describes that the gastrocnemius is separated by the medial and the lateral fibers and may be moved to sides by the vector
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value starting on the elbow [30]. For example, when the internal branch shrinks strongly, the internal spread of elbow bones may occur and when the side branch shrinks strongly, the external spread may occur. Therefore, this study, based on such mechanism, proves that the application on fatigue occurred gastrocnemius reduces the body’s side unrest by recovering the muscle fatigue. However, when applied to patients having slow feet symptoms due to brain injuries, other results regarding the postural control are considered to be occurred. Therefore if TENS is clinically applied to brain injury patients on the fatigue occurred gastrocnemius after the walking training, it is expected to be helpful to improve the postural control due to reduced muscle fatigue. Also, as the tense is released, the fall is considered to be prevented with stabilized postural control during walking. And various measures to reduce the postural sway and continuous researches is required in the future.
5. Conclusion The purpose of this study is to find the difference impacting on the postural sway depending on the visual input’s existence when TENS is applied to the dorsiflexor and the plantarflexor after fatigue occurring movements. As conclusion, when TENS is applied on the foot top and the plantarflexor for a normal person while the visual information is blocked, the effect is shown only on the plantarflexor. Therefore the clinical application of TENS on the peroneal muscle is effective on the postural control and is considered to be helpful to prevent fall by improving stabilized postural control with the visual input.
References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]
Horak FB, Shupert CL, Mirka A. Components of postural dyscontrol in the elderly: A review. Neurobiol Aging. 1989; 10(6):727-38. Collins JJ, De Luca CJ. The effects of visual input on open-loop and closed-loop postural control mechanisms. Exp Brain Res. 1995;103(1):151-63. Gurfinkel VS, Ivanenko YuP, Levik YuS, Babakova IA. Kinesthetic reference for human orthograde posture. Neuroscience. 1995;68(1):229-43. Kavounoudias A, Gilhodes JC, Roll R, Roll JP. From balance regulation to body orientation: two goals for muscle proprioceptive information processing? Exp Brain Res. 1999;124(1):80-8. Vouriot A, Gauchard GC, Chau N, Benamghar L, Lepori ML, Mur JM, et al. Sensorial organisation favouring higher visual contribution is a risk factor of falls in an occupational setting. Neurosci Res. 2004;8(3):239-47. Vuillerme N, Danion F, Forestier N, Nougier V. Postural sway under muscle vibration and muscle fatigue in humans. Neurosci Lett. 2002;333(2):131-5. Gimmon Y, Riemer R, Oddsson L, Melzer I. The effect of plantar flexor muscle fatigue on postural control. J Electromyogr Kinesiol. 2011;21(6):922-8. Di Giulio I, Maganaris CN, Baltzopoulos V, Loram ID. The proprioceptive and agonist roles of gastrocnemius, soleus and tibialis anterior muscles in maintaining human upright posture. J Physiol. 2009;587(10):2399-416. Gribble PA, Hertel J. Effect of hip and ankle muscle fatigue on unipedal postural control. J Electromyogr Kinesiol. 2004;14(6):641-6. Nam HS, Park DS, Kim DH, Kang HJ, Lee DH, Lee SH, et al. The relationship between muscle fatigue and balance in the elderly. Ann Rehabil Med. 2013;37(3):389-95. Yaggie JA, McGregor SJ. Effects of isokinetic ankle fatigue on the maintenance of balance and postural limits. Arch Phys Med Rehabil. 2002;83(2):224-8. Bellew JW, Fenter PC. Control of balance differs after knee or ankle fatigue in older women. Arch Phys Med Rehabil. 2006;87(11):1486-9. Wojtys EM, Wylie BB, Huston LJ. The effects of muscle fatigue on neuromuscular function and anterior tibial translation in healthy knees. Am J Sports Med. 1996;24(5):615-21.
402 [14]
J. Yu et al. / The effect of transcutaneous electrical nerve stimulation on postural sway
Cho HY, Lee SH, In TS, Lee KJ, Song CH. Effect of transcutaneous electrical nerve stimulation(TENS) on changes in postural balance and muscle contraction following muscle fatigue. Journal of Physical Therapy Science. 2011;23(6):899903. [15] Sluka KA, Walsh D. Transcutaneous electrical nerve stimulation: Basic science mechanisms and clinical effectiveness. J Pain. 2003;4(3):109-21. [16] Yoon JG, Ryu JJ, Roh HW, Yang HA, Lee SB. Effect of transcutaneous electrical nerve stimulation(TENS), self stretching and functional massage on the muscule fatigue by maximum muscular strength. J Int Acad Phys Ther Res. 2012;3(2):422-8. [17] Cho HY, In TS, Cho KH, Song CH. A single trial transcutaneous electrical nerve stimulation(TENS) Improves spasticitiy and balance in patients with chronic stroke. Tohoku J Exp Med. 2013;229(3):187-93. [18] Ping Ho, Chung B, Kam Kwan Cheng B. Immediate effect of transcutaneous electrical nerve stimulation on spasticity in patients with spinal cord injury. Clin Rehabil. 2010;24(3):202-10. [19] Ng SS, Hui-Chan CW. Does the use of TENS increase the effectiveness of exercise for improving walking after stroke? A randomized controlled clinical trial. Clin Rehabil. 2009; 23(12):1093-103. [20] Ng SS, Hui-Chan CW. Transcutaneous electrical nerve stimulation combind with task-related training improves lower limb functions in subjects with chronic stroke. Stroke. 2007; 38(11):2953-9. [21] Tyson SF, Sadeghi-Demneh E, Nester CJ. The effects of transcutaneous electrical nerve stimulation on strength, proprioception, balance and mobility in people with stroke: a randomized controlled cross-over trial. Clin Rehabil. 2013; 27(9):785-91. [22] Dickstein R, Laufer Y, Katz M. TENS to the posterior aspect of the legs decreases postural sway during stance. Neurosci Lett. 2006;393(1):51-5. [23] Laufer Y, Dickstein R. TENS to the lateral aspect of the knees during stance attenuates postural sway in young adults. Scientific World Journal. 2007;26(7):1904-11. [24] Armutlu K, Meric A, Kirdi N, Yakut E, Karabudak R. The effect of transcutaneous electrical nerve stimulation on spasticity in multiple sclerosis patients: A pilot study. Neurorehabil Neural Repair. 2003;17(2):79-82. [25] Miller L, Mattison P, Paul L, Wood L. The effects of transcutaneous electrical nerve stimulation (TENS) on spasticity in multiple sclerosis. Mult Scler. 2007;13(4):527-33. [26] Ebig M, Lephart SM, Burdett RG, Miller MC, Pincivero DM. The effect of sudden inversion stress on EMG activity of the peroneal and tibialis anterior muscles in the chronically unstable ankle. Orthopaedic J Orthop Sports Phys Ther. 1997;26(2):73-7. [27] Tilp M, Steib S, Herzog W. Length changes of human tibialis anterior central aponeurosis during passive movements and isometric, concentric, and eccentric contractions. Eur J Appl Physiol. 2012;112(4):1485-94. [28] Choi YM, Kim BC. Muscle fiber characteristics, myofibrillar protein isoforms, and meat quality. Livestock Science. 2009;122(2):105-18. [29] Borg F, Finell M, Hakala I, Herrala M. Analyzing gastrocnemius EMG-activity and sway data from quiet and perturbed standing. J Electromyogr Kinesiol. 2007;17(5):622-34. [30] Duysens J, van Wezel BM, Prokop T, Berger W. Medial gastrocnemius is more activated than lateral gastrocnemius in sural nerve induced reflexes during human gait. Brain Res. 1996;727(1-2):230-32.
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