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The effect of different skin-ankle brace application pressures on quiet single-limb balance and electromyographic activation onset of lower limb muscles

The effect of different skin-ankle brace application pressures on quiet single-limb balance and... Background: Several studies have been carried out in order to investigate the effect of ankle bracing on ankle joint function and performance. However, no study so far has examined the role of skin-brace interface pressure in neuromuscular control. The aim of this study was to investigate the effect of different skin-ankle brace interface pressures on quiet single limb balance and the electromyographic (EMG) activation sequence of four lower limb muscles. Methods: Thirty three male physical education students who volunteered to take part in the study were measured under three ankle brace conditions: i) without brace, ii) with brace and 30 kPa application pressure and iii) with brace and 60 kPa application pressure. Single limb balance (anteroposterior and mediolateral parameter) was assessed on the dominant lower limb, with open and closed eyes, on a force platform, simultaneously with the EMG recording of four lower lower limb muscles' (gastrocnemius, peroneus longus, rectus femoris and biceps femoris) activation onset. Results: The results showed that overall balance (total stability parameter) was not significantly affected in any of the three ankle brace conditions. However, the anteroposterior centre of pressure excursion and centre of pressure excursion velocity were significantly increased with the application of ankle brace, both with 30 and 60 kPa application pressures. Furthermore, it was found that single limb balance was significantly worse with closed eyes compared to open eyes. EMG measurements showed that the sequence of lower limb activation onset was not affected in any of the three ankle brace application conditions. The results of this study showed that the application of an ankle brace with two different skin-brace interface pressures had no effect on overall single limb balance and the sequence of lower limb muscle activation. Conclusion: These findings suggest that peripheral joint receptors are either not adequately stimulated by the brace application and therefore are not able to alter the balance control strategy of the CNS, or that they play a less important role in the control of single limb balance. Further research is needed in this area with more dynamic and functional measurements, before the safe use of ankle bracing can be widely recommended. Page 1 of 8 (page number not for citation purposes) BMC Musculoskeletal Disorders 2007, 8:89 http://www.biomedcentral.com/1471-2474/8/89 sequence during standing balance is an important param- Background Ankle bracing comprises one of the most common pro- eter which is related to ankle joint neuromuscular func- phylactic measures used during competition by sports tion. Specifically, it was considered important in this participants, in order to prevent lateral ankle sprains. Sev- study to investigate whether the application of an ankle eral experimental studies have been carried out in order to brace with different pressures affects only the activation investigate the effect of ankle bracing on athletic perform- sequence of four muscles, and not the overall EMG activ- ance and other parameters related to function. However, ity during the 5 sec trial, either due to the stimulation of the effect of ankle bracing on balance and postural control the skin receptors or to the restriction of joint motion. In has been investigated by a limited number of studies that a previous study, Roller et al [7] investigated the role of a have demonstrated both positive and negative findings. semirigid ankle brace in the mediolateral and anteropos- Bennell & Goldie [1], showed that application of a Swede- terior single limb balance, as well as the activation o laced-up brace, and adhesive tape reduced the one-leg- sequence of four lower limb muscles and the abdominals ged stability of uninjured subjects significantly. Similarly, and low back muscles. The results showed no significant Papadopoulos et al. [2], found that the application of a difference in AP and ML balance ability and EMG activa- laced-up ankle brace deteriorated significantly single and tion time between the conditions with and without brace, double limb balance in young healthy volunteers. It was which is in aggreement with the findings of the current speculated that this might be due to the restriction of study. In another study by Rose et al [8], it was found that ankle mobility caused by these supports. Therefore, this the application of semirigid orthotic ankle support did negative effect may be either due to an inhibiting effect of not affect the sequence of four knee muscles during the brace on peripheral receptors, or to the reduction of dynamic single limb balance in subjects with overprona- ankle range of motion that might interfere with the com- tion of the foot. To the best of our knowledge, these are pensatory balance correcting strategies. On the other the only studies that have investigated the role of ankle hand, Baier & Hopf [3] showed that a rigid and a semirigid bracing in lower limb muscles activation sequence, and ankle brace significantly improved balance in a group of therefore further research is needed. Furthermore, no athletes with instability but had no effect on a healthy studies have investigated or reported what the average control group. Furthermore, in another study by Feuer- brace application pressure is for different brace types. The bach and Grabiner [4], it was found that the application importance of studying muscle activation onset during a of an air-stirrup ankle brace, significantly improved pos- balance task has been demonstrated by several studies [9- tural control of healthy young subjects, since it reduced 11], which described the different strategies used by a per- both the centre of pressure excursion and centre of pres- son to maintain an upright posture during static [9,10] or sure excursion velocity during single limb balance. dynamic balance tasks [12-17], both in healthy and in idi- viduals with proprioception deficit. Clearly, there is a Friden et al. [5], who also investigated the effect of an air- need for further research in order to establish the role of stirrup ankle brace on the single limb balance of patients brace application pressure on balance and propriocep- with lateral ankle sprains, found no positive or negative tion. effect on centre of pressure excursion and centre of pres- sure excursion velocity. Likewise, Palmieri et al. [6], who Therefore, the purpose of this study was to investigate the investigated the effect of 4 days ankle-brace use on the effect of different skin-brace interface application pres- mean frequency amplitude of the mediolateral and anter- sures on quiet single-limb static balance and whether the oposterior centre of pressure during one-legged stance, in balance maintenance strategies during a single limb 28 young healthy college students, found no difference stance, can be altered with the application of a specific between the brace and control conditions. They con- widely used type of ankle brace the sequence of lower cluded that ankle-brace application did not interfere with limb muscle activation during balance. the proprioceptive control of posture during one-legged stance. However, no information is provided regarding Methods the amount of pressure that the brace was applied by the Thirty-three male physical education students, volun- subjects. teered to take part in the study. The experimental investi- gation with human subjects reported in the manuscript According to all these studies, controversy seems to exist was performed with informed consent and followed all as to the effect of ankle bracing on postural control due to the guidelines for experimental investigation with human methodological differences of balance assessment, type of subjects required by the institutional review board and the brace used and technique application. Furthermore, a lim- ethics committee with which the principal investigators ited number of studies have been carried out so far to are affiliated. Subjects had no history of severe ankle investigate the effect of ankle bracing on EMG activation sprains and joint instability and did not ever make use of time of lower limb muscles. Lower limb activation an ankle brace or any other type of ankle support. Eligible Page 2 of 8 (page number not for citation purposes) BMC Musculoskeletal Disorders 2007, 8:89 http://www.biomedcentral.com/1471-2474/8/89 subjects that were entered to the study underwent anthro- all subjects. The Tekscan mat calibration was done using a pometric measurements (Table 1), and were followed by Uniform Bladder System, described by Nicolopoulos [18]. the assessment of the single limb balance with open and closed eyes in conjunction with the EMG activation time A combined stability parameter (σ ), described by Riley et measurements, under three conditions: i) without brace; al. [19], was also used for the overall balance assessment, ii) with brace and 30 kPa application pressure; and iii) which is based on the root mean square variance of both with brace and 60 kPa application pressure. A moderate the centre of pressure excursion and centre of pressure and a high application pressure were chosen because prac- excursion velocity in the anteropostreior and mediolateral tically, athletes apply ankle braces subjectively, according direction according to the formula: to the level of support and comfort they prefer. Comfort 2 2 means better performance and support better injury pre- σ = √σ + σ r AP r Latr r vention and the criterion for this choice lies with the indi- vidual so far, since no study exists to support any of these where: σ is the combined stability parameter; σ and r AP r parameters. Brace application pressure of 30 kPa resem- σ are the directional anteroposterior and mediolateral Latr r bles a moderately tightened brace and may be chosen by stability parameters correspondingly. some sports participants in order to be more comfortable and to not hinder their performance. On the other hand, The stability parameter was calculated in order to have a 60 kPa brace application resembles a highly tight applica- picture of the brace application on the total balance. Sub- tion with none of the subjects however reporting pain, jects were asked to stand on their dominant foot (which discomfort, discolouration or microcirculation distur- was determined by asking them to pretend to kick a ball, bances, in this study. This tight application may be chosen with the kicking leg being the dominant), for 5 seconds as by sports participants whose main concern is to prevent quietly as possible, staring at a 3 cm spot fixed one meter ankle injury or re-injury. Furthermore, 60 kPa application on the wall in front of them (Figure 1). Balance was meas- pressure is safe because it is significantly lower than the ured with open and closed eyes and a mean of two trials skin pressure threshold of 100 kPa which causes skin for each condition was calculated. The same procedure breakage [20]. Since ankle brace application pressures was repeated for all three ankle brace conditions. have not been measured by previous studies, this is a first attempt to apply pressures as close as possible to the com- Interface pressure was measured with the 9811 F-Socket monly used application techniques by sports participants, (Teckscan Inc., Boston, MA) sensor which was applied in for the above reasons. the anterior aspect of the ankle underlying the brace laces. The F-Socket was calibrated using a sphygmomanometer The laced-up McDavid ankle brace (McDavid Ankle around the ankle joint up to the point where the desired Guard Inc., Chicago, IL) was used for the measurements pressures (30 & 60 kPa) were reached. in the study. Pressure was applied by tightening the laces until the pre- Single limb balance assessment determined amount of pressure (30 & 60 kPa) was Single limb balance was assessed using the MatSCAN reached (Figure 2). The two pressures were chosen force platform (Tekscan Inc., Boston, MA) which dis- because according to Convery & Bui [20], any pressure of played the average centre of pressure (COP) excursion and 100 kPa and above can cause skin damage, therefore the centre of pressure excursion velocity in the anteroposte- higher pressure of 60 kPa was much below that level and rior and mediolateral directions. All measurements the 30 kPa was chosen as a moderate pressure. Further- described in the study were performed without shoes. All more, according to Meinders et al [21], pressures of 40 kPa measurements, in all subjects, were performed firstly and over can temporarily stop microcirculation but cause without brace, secondly with brace and 30 kpa pressure immediate hyperaemia immediately after pressure is and thirdly with brace and 60 kPa pressure. For this rea- removed. Since the brace was removed after each experi- son an order effect was ruled out, since it was the same for ment there was no incident of skin irritation or damage. Table 1: Demographic variables (N = 33) EMG measurements The effect of the McDavid ankle brace on the sequence of Age 21.5 ± 1.5 Weight (kgrs) 77.9 ± 8.9 lower limb EMG muscle activation was measured simulta- Height (cm) 177.5 ± 7.4 neously with the balance measurements. Surface Electro- BMI 24.8 ± 2.9 myography (EMG) was used to determine the activation Fat (%) 19.9 ± 4.1 time of the gastrocnemius, peroneous longus, rectus fem- Lean Body Mass 62.2 ± 6.1 oris and biceps femoris muscles, using a pair of bipolar Activity level 8.5 ± 1.5 surface silver chloride electrodes. These muscles were Page 3 of 8 (page number not for citation purposes) BMC Musculoskeletal Disorders 2007, 8:89 http://www.biomedcentral.com/1471-2474/8/89 Ski and 30 kPa (right) p Figure 2 n-ankle brace inte ressure applica rface pressure pattern for tion conditions 60 kPa (left) Skin-ankle brace interface pressure pattern for 60 kPa (left) and 30 kPa (right) pressure application conditions. between 20 and 500 Hz, in order to subtract electromag- netic noise, and movement artefacts were filtered with a high pass cut off frequency of 20 Hz [25]. The first visible signal that was 2 SDs above baseline activity was consid- ered as the onset of muscle activation [12,15,16]. Statistical analysis Statistical analysis was performed with the SPSS version 11.5. In order to analyze differences for balance and EMG measurements between the three ankle brace conditions, as well as for open and closed eyes and the eyes by brace interactions, the two way ANOVA was used. The Bonfer- onni test was applied for post-hoc comparisons in order to calculate the range of differences and the mean differ- Sing Figure 1 le limb balance and muscle activation measurement ences, together with the 95% confidence interval. The Single limb balance and muscle activation measurement. paired t-test and the mixed effects ANOVA model on the other hand were used to calculate differences for the sta- selected because according to the literature they have been bility parameter. Since balance was measured twice on the used by previous studies for the EMG measurement dur- same individual, once with open and another time with ing single limb balance and are of significant importance closed eyes, a paired t-test was used to calculate the differ- in the control strategy of standing balance [10,17]. ence in stability parameter between open and closed eyes. The Biopac MP100 System (BiopacSystems, Inc, Goleta, Similarly, as the balance for the 3 ankle brace conditions CA) was used to record and analyse the EMG signal. After was measured three times on the same individual, a mixed the skin was shaved and degreased with 70% alcoholic effects ANOVA model was used to calculate the differ- solution, electrodes were attached to the skin parallel to ences in the stability parameter between the three brace the muscle fibres, on the most prominent point of the conditions taking also into account the correlation muscles [22-24], during isometric contraction and palpa- between adjacent observations. For the assessing the sta- tion, according to the specifications by Perotto [24], and tistical significance of a hypothesis a common significance an interelectrode distance of 3 cm. Correct placement of level of 5% was assumed. the electrodes was tested for crosstalk by asking the sub- jects to perform active contractions of all four muscles that Results Single limb balance were measured. The ground electrodes ware placed on bony prominences of the knee and ankle. The raw EMG Mean values for the centre of pressure excursion (mm) signal was sampled by the computer with a frequency of and centre of pressure excursion velocity (mm/sec), in the 1000 Hz. Processing of the raw EMG signal was per- mediolateral and anteroposterior direction are displayed formed by converting it to RMS, band pass filtrered in Tables 2 and 3. No significant differences were found in Page 4 of 8 (page number not for citation purposes) BMC Musculoskeletal Disorders 2007, 8:89 http://www.biomedcentral.com/1471-2474/8/89 Table 3: Mean values for the anteroposterior sway and sway the mediolateral centre of pressure excursion and centre of velocity for three ankle brace conditions with open and closed pressure excursion velocity between the three ankle brace eyes (N = 33) conditions (F = 0.29, df = 2, p = 0.749) (Table 2). Anteropostreior sway Anteroposterior sway (mm) velocity (mm/sec) In the anteroposterior direction however, significant dif- ferences were found between the condition with 30 kPa Open eyes Closed Open eyes Closed brace application and the condition without brace (mean eyes eyes difference = 3.08, 95% CI: 0.06–6.1; p = 0.043) and between the condition with 60 kPa brace application and Ankle x ± SD x ± SD x ± SD x ± SD the condition without brace (mean difference = 3.09, 95% brace CI: 0.08–6.11; p = 0.042). Specifically, ankle brace appli- condition Without 14.8 ± 3.09 25.64 ± 118.06 ± 205.12 ± cation resulted in a deterioration of the anteroposterior brace 7.99** 24.08 63.9** COP excursion and excursion velocity, both with open With brace 15.39 ± 31.23 ± 123.15 ± 249.8 ± and closed eyes (Table 3). As far as the effect of vision is (30 kPa) 3.99 9.88** 31.9 79.02** concerned, significant differences were found between With brace 16.41 ± 30.24 ± 131.45 ± 241.88 ± open and closed eyes, both in the mediolateral (F = 22.3, (60 kPa) 4.44 10.1** 35.1 80.5** df = 1, 192, p < 0.001) and the anteroposterior (F = 175.4, ** F = 22.8, df = 1, p < 0.001 for the difference between open and df = 1, 192, p < 0.001) direction, in all three ankle brace closed eyes in Velocity application pressure conditions, with single limb balance being significantly worse with closed eyes. (Tables 2 and EMG Measurements 3). Analysis of variance showed that there were no significant differences in the activation time of the peroneus longus As far as the stability parameters are concerned, no signif- (F = 0.008, df = 2, p = 0.99), gastrocnemius (F = 0.28, df = icant differences were detected in single limb balance 2, p = 0.75), rectus femoris (F = 1.13, df = 2, p = 0.32) and between the three brace application conditions, in the biceps femoris (F = 2.11, df = 2, p = 0.124), between the anteroposterior (F = 2.12, df = 2, p = 0.13), mediolateral three ankle brace application conditions. Furthermore, no (F = 0.05, df = 2, p = 0.95) and the total (F = 0.26, df = 1, significant differences in EMG activation time were found p = 0.77) stability parameters. Lastly, significant differ- in single limb balance between open and closed eyes for ences were found in the total stability parameter between the peroneus longus, gastrocnemius and rectus femoris open and closed eyes (F = 2.24, df = 32, p = 0.032). Table muscles. However, significantly faster activation of the 4 displays the mean values and standard deviations of the biceps femoris muscle was detected with open eyes as stability parameters for the three ankle brace and eye con- compared to closed eyes, in all three brace conditions. ditions. Mean EMG activation time values are displayed in Table 5. No change in the EMG activation time sequence was observed for the four lower limb muascles that were tested in the three brace application conditions (Table 6). Table 2: Mean values for mediolateral sway and sway velocity for Discussion three ankle brace conditions with open and closed eyes (N = 33) To the best of our knowledge, this study is the first to investigate the effects of ankle brace application pressures Medioliateral sway Medioliateral sway (mm) velocity (mm/sec) on postural control and electromyographic activation sequence of lower limb muscles. In a recent study, Papa- Open eyes Closed Open eyes Closed Table 4: Mean values for the anteroposterior (σ ), mediolateral eyes eyes Apr (σ ) and total (σ ) stability parameters for open and closed eyes Latr r and the three ankle brace conditions (N = 33) Ankle x ± SD x ± SD x ± SD x ± SD brace Condition σ σ σ Apr Latr r condition Without 36.04 ± 52.8 ± 290.2 ± 423.6 ± Open eyes 21.83 ± 11.4 131.65 ± 103.3 136.41 ± 99.9 brace 23.2 28.0* 184.2 224.2* With brace 34.2 ± 22.7 48.5 ± 275.06 ± 401.0 ± Closed eyes 69.9 ± 39.5 152.17 ± 85.3 174.45 ± 79.87 (30 kPa) 21.2* 183.7 185.5* Without brace 65.84 ± 45.5 116.09 ± 119.3 145.2 ± 113.7 With brace 35.2 ± 23.8 50.9 ± 284.03 ± 407.4 ± With brace 30 92.68 ± 54.8 118.71 ± 90.12 162.5 ± 85.3 (60 kPa) 19.2* 188.8 153.6* kPa With brace 60 79.05 ± 54.8 124.08 ± 94.6 157.3 ± 93.7 kPa * F = 22.3, df = 1, p < 0.001 for the difference between open and closed eyes Page 5 of 8 (page number not for citation purposes) BMC Musculoskeletal Disorders 2007, 8:89 http://www.biomedcentral.com/1471-2474/8/89 Table 5: Mean EMG activation times (msec), of lower limb muscles, for the three ankle brace conditions with open (OE) and closed eyes (CE) (N = 33) Peroneous longous Gastrocnemius Rectus Femoris Biceps Femoris Ankle brace condition OE CE OE CE OE CE OE CE Without brace 31.7 ± 6.3 30.7 ± 6.4 33.06 ± 7.07 32.3 ± 6.4 117.06 ± 31.2 117.87 ± 35.9 118.5 ± 27.1 123.8 ± 34.7 With brace (30 kPa) 31.2 ± 5.2 31.1 ± 6.8 32.2 ± 5.4 31.5 ± 6.7 111.8 ± 22.1 125.1 ± 28.4 118.8 ± 26.4 143.1 ± 42.8 With brace (60 kPa) 31.6 ± 5.5 30.5 ± 6.3 32.5 ± 7.3 32.2 ± 6.1 127.8 ± 35.1 121.69 ± 26.2 119.2 ± 27.5 123.5 ± 25.4 dopoulos et al. [26], examined the effects of different posterior (σ ) stability parameters, as well as the total Latr ankle brace application pressures on the peroneus longus stability parameter (σ ), were not significantly affected, it reaction time, during a sudden inversion stress test and may be concluded that overall, the application of the two found that ankle brace application with medium and high different ankle brace application pressures, had no posi- pressure, resulted in a significant delay of the peroneal tive or negative effect on quiet single limb balance. This is reaction time. In the current study, we investigated the also supported by Riley et al. [7], who stated that the sta- effect of no brace application and two different ankle bility parameter they calculated, which combines both the brace application pressures, on single limb balance con- centre of pressure excursion and centre of pressure excur- trol and the electromyographic activation sequence of sion velocity, as well as the mediolateral and anteroposte- four lower limb muscles. The results showed that overall rior planes, is more valid and representative for the with the specific type of brace that was used in this study, assessment of standing balance than separately assessing postural control, as assessed by the total stability parame- each of these parameters alone. This information may be ter 'σ ', was not positively or adversely affected by the two useful in future studies as well as in the clinical setting, different brace application pressures. This finding is in since it seems that the application of the laced-up ankle agreement with previous studies, which showed that brace with a moderate and a high pressure, had no signif- ankle bracing had no effect on postural control, without icant stimulation effect on the peripheral, mainly skin however, referring to the pressure of brace application receptors, and therefore afferent signals were not strong [5,6]. It was also shown that different ankle brace applica- enough to provoke a specific central response and affect tion pressures had no effect on the mediolateral plane but single limb balance control. Another finding of this study on the other hand, it significantly deteriorated balance in was that single limb balance was significantly worse with the anteroposterior plane. These findings are partly in closed eyes as compared to open eyes. This is in agreement agreement with Bennell & Goldie [1], and Papadopoulos with previous studies [2,28-31] and further establishes the et al. [2], who also found that ankle bracing adversely importance of vision which is one of the three major affected balance in young healthy volunteers. However, sources of balance control together with the vestibular sys- the fact that mediolateral balance was not affected in any tem and the peripheral joint receptors [32]. of the three brace application conditions may be more valid in this research since in this study sample, the COP The results of the electromyographic measurements trajectory during single limb balance, mainly traveled in showed that the sequence of lower limb muscle activation the mediolateral direction. The deterioration of balance in onset was not altered by the application of two different the anteroposterior direction may also be attributed to the ankle brace application pressures. This finding cannot be fact that muscular control of single limb balance which is compared with previous studies since this is the only more efficient in the AP direction [27], was adversely study that has investigated the effect of ankle bracing on affected by the application of the ankle brace. Further- the EMG activity of lower limb muscles and, as mentioned more, since both the mediolateral (σ ) and the antero- above, the only that has examined the effect of different Apr Table 6: EMG activation sequence of lower limb muscles during single limb balance in the three brace application conditions Brace condition EYES Peroneus longus Gastrocnemius Rectus femoris Biceps femoris Without brace Open 1 2 3 4 Closed 1 2 3 4 With brace (30 kPa) Open 1 2 3 4 Closed 1 2 3 4 With brace (60 kPa) Open 1 2 4 3 Closed 1 2 3 4 Page 6 of 8 (page number not for citation purposes) BMC Musculoskeletal Disorders 2007, 8:89 http://www.biomedcentral.com/1471-2474/8/89 brace application pressures. However, useful information Competing interests that arises is that different ankle brace application pres- The authors declare that they have no competing interests. sures do not change the ankle strategy of balance control, which is the one that dominates during balance of young Authors' contributions healthy subjects [15,10,14,9,33]. Therefore, the fact that ESP, CN, and AB participated in the design of the study, the more distal peroneus longus and gastrocnemius mus- data acquisition and analysis and writing of this manu- cles were activated faster than the more proximal thigh script. GV, participated in the analysis and writing of this muscles (rectus femoris and biceps femoris), both in the paper. SAP and SA participated in the analysis and also in condition without brace and the conditions with moder- revising critically the manuscript. All authors read and ate and high brace application pressures, further supports approved the final manuscript. the hypothesis that the central nervous system (CNS) does not alter its single limb balance control strategy. Several Acknowledgements The authors wish to thank Mr. Vasilios Nikolaou for his contribution to the explanations may be given for this observation: first, the statistical analysis of this study. skin receptors are either not adequately stimulated by the high application pressure of the brace so as, in turn, to References provoke a CNS response, or their role in controlling single 1. Bennell KL, Goldie PA: The differential effects of external ankle limb balance is less important. Second, the fact that the support on postural control. J Orthop Sport Phys Ther 1994, study sample consisted of non-injured subjects, may in 20(6):287-295. 2. 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The Foot 2005, 15:175-179. 27. Loram ID, Maganaris CN, Lakie M: Human postural sway results from frequent, ballistic bias impulses by soleus and gastroc- nemius. Journal of Physiology 2005, 564:295-311. 28. Bernier JN, Perrin DH: Effect of coordination training on prop- rioception of the functionally unstable ankle. J Orthop Sport Phys Ther 1998, 27(4):264-275. 29. Goldie PA, Bach TM, Evans OM: Force platform measures for evaluating postural control: reliability and validity. Arch Phys Med Rehab 1989, 70(7):510-517. 30. Goldie PA, Evans OM, Bach TM: Steadiness in one-legged stance: development of a reliable force-platform testing procedure. Arch Phys Med Rehab 1992, 76:348-354. 31. Perrin PP, Bene MC, Durupt D: Ankle trauma significantly impairs posture-a study in basketball players and controls. Int J Sports Med 1997, 18:387-392. 32. Lephart SM, Pincivero DM, Rozzi SL: Proprioception of the ankle and knee. Sports Med 1998, 25:149-155. 33. Yaggie JA, McGregor SJ: Effects of isokinetic ankle fatigue on the maintenance of balance and postural limits. Arch Phys Med Rehab 2002, 83:224-228. Pre-publication history The pre-publication history for this paper can be accessed here: http://www.biomedcentral.com/1471-2474/8/89/prepub Publish with Bio Med Central and every scientist can read your work free of charge "BioMed Central will be the most significant development for disseminating the results of biomedical researc h in our lifetime." 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The effect of different skin-ankle brace application pressures on quiet single-limb balance and electromyographic activation onset of lower limb muscles

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Springer Journals
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Copyright © 2007 by Papadopoulos et al; licensee BioMed Central Ltd.
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Medicine & Public Health; Orthopedics; Rehabilitation; Rheumatology; Sports Medicine; Internal Medicine; Epidemiology
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10.1186/1471-2474-8-89
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17850663
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Abstract

Background: Several studies have been carried out in order to investigate the effect of ankle bracing on ankle joint function and performance. However, no study so far has examined the role of skin-brace interface pressure in neuromuscular control. The aim of this study was to investigate the effect of different skin-ankle brace interface pressures on quiet single limb balance and the electromyographic (EMG) activation sequence of four lower limb muscles. Methods: Thirty three male physical education students who volunteered to take part in the study were measured under three ankle brace conditions: i) without brace, ii) with brace and 30 kPa application pressure and iii) with brace and 60 kPa application pressure. Single limb balance (anteroposterior and mediolateral parameter) was assessed on the dominant lower limb, with open and closed eyes, on a force platform, simultaneously with the EMG recording of four lower lower limb muscles' (gastrocnemius, peroneus longus, rectus femoris and biceps femoris) activation onset. Results: The results showed that overall balance (total stability parameter) was not significantly affected in any of the three ankle brace conditions. However, the anteroposterior centre of pressure excursion and centre of pressure excursion velocity were significantly increased with the application of ankle brace, both with 30 and 60 kPa application pressures. Furthermore, it was found that single limb balance was significantly worse with closed eyes compared to open eyes. EMG measurements showed that the sequence of lower limb activation onset was not affected in any of the three ankle brace application conditions. The results of this study showed that the application of an ankle brace with two different skin-brace interface pressures had no effect on overall single limb balance and the sequence of lower limb muscle activation. Conclusion: These findings suggest that peripheral joint receptors are either not adequately stimulated by the brace application and therefore are not able to alter the balance control strategy of the CNS, or that they play a less important role in the control of single limb balance. Further research is needed in this area with more dynamic and functional measurements, before the safe use of ankle bracing can be widely recommended. Page 1 of 8 (page number not for citation purposes) BMC Musculoskeletal Disorders 2007, 8:89 http://www.biomedcentral.com/1471-2474/8/89 sequence during standing balance is an important param- Background Ankle bracing comprises one of the most common pro- eter which is related to ankle joint neuromuscular func- phylactic measures used during competition by sports tion. Specifically, it was considered important in this participants, in order to prevent lateral ankle sprains. Sev- study to investigate whether the application of an ankle eral experimental studies have been carried out in order to brace with different pressures affects only the activation investigate the effect of ankle bracing on athletic perform- sequence of four muscles, and not the overall EMG activ- ance and other parameters related to function. However, ity during the 5 sec trial, either due to the stimulation of the effect of ankle bracing on balance and postural control the skin receptors or to the restriction of joint motion. In has been investigated by a limited number of studies that a previous study, Roller et al [7] investigated the role of a have demonstrated both positive and negative findings. semirigid ankle brace in the mediolateral and anteropos- Bennell & Goldie [1], showed that application of a Swede- terior single limb balance, as well as the activation o laced-up brace, and adhesive tape reduced the one-leg- sequence of four lower limb muscles and the abdominals ged stability of uninjured subjects significantly. Similarly, and low back muscles. The results showed no significant Papadopoulos et al. [2], found that the application of a difference in AP and ML balance ability and EMG activa- laced-up ankle brace deteriorated significantly single and tion time between the conditions with and without brace, double limb balance in young healthy volunteers. It was which is in aggreement with the findings of the current speculated that this might be due to the restriction of study. In another study by Rose et al [8], it was found that ankle mobility caused by these supports. Therefore, this the application of semirigid orthotic ankle support did negative effect may be either due to an inhibiting effect of not affect the sequence of four knee muscles during the brace on peripheral receptors, or to the reduction of dynamic single limb balance in subjects with overprona- ankle range of motion that might interfere with the com- tion of the foot. To the best of our knowledge, these are pensatory balance correcting strategies. On the other the only studies that have investigated the role of ankle hand, Baier & Hopf [3] showed that a rigid and a semirigid bracing in lower limb muscles activation sequence, and ankle brace significantly improved balance in a group of therefore further research is needed. Furthermore, no athletes with instability but had no effect on a healthy studies have investigated or reported what the average control group. Furthermore, in another study by Feuer- brace application pressure is for different brace types. The bach and Grabiner [4], it was found that the application importance of studying muscle activation onset during a of an air-stirrup ankle brace, significantly improved pos- balance task has been demonstrated by several studies [9- tural control of healthy young subjects, since it reduced 11], which described the different strategies used by a per- both the centre of pressure excursion and centre of pres- son to maintain an upright posture during static [9,10] or sure excursion velocity during single limb balance. dynamic balance tasks [12-17], both in healthy and in idi- viduals with proprioception deficit. Clearly, there is a Friden et al. [5], who also investigated the effect of an air- need for further research in order to establish the role of stirrup ankle brace on the single limb balance of patients brace application pressure on balance and propriocep- with lateral ankle sprains, found no positive or negative tion. effect on centre of pressure excursion and centre of pres- sure excursion velocity. Likewise, Palmieri et al. [6], who Therefore, the purpose of this study was to investigate the investigated the effect of 4 days ankle-brace use on the effect of different skin-brace interface application pres- mean frequency amplitude of the mediolateral and anter- sures on quiet single-limb static balance and whether the oposterior centre of pressure during one-legged stance, in balance maintenance strategies during a single limb 28 young healthy college students, found no difference stance, can be altered with the application of a specific between the brace and control conditions. They con- widely used type of ankle brace the sequence of lower cluded that ankle-brace application did not interfere with limb muscle activation during balance. the proprioceptive control of posture during one-legged stance. However, no information is provided regarding Methods the amount of pressure that the brace was applied by the Thirty-three male physical education students, volun- subjects. teered to take part in the study. The experimental investi- gation with human subjects reported in the manuscript According to all these studies, controversy seems to exist was performed with informed consent and followed all as to the effect of ankle bracing on postural control due to the guidelines for experimental investigation with human methodological differences of balance assessment, type of subjects required by the institutional review board and the brace used and technique application. Furthermore, a lim- ethics committee with which the principal investigators ited number of studies have been carried out so far to are affiliated. Subjects had no history of severe ankle investigate the effect of ankle bracing on EMG activation sprains and joint instability and did not ever make use of time of lower limb muscles. Lower limb activation an ankle brace or any other type of ankle support. Eligible Page 2 of 8 (page number not for citation purposes) BMC Musculoskeletal Disorders 2007, 8:89 http://www.biomedcentral.com/1471-2474/8/89 subjects that were entered to the study underwent anthro- all subjects. The Tekscan mat calibration was done using a pometric measurements (Table 1), and were followed by Uniform Bladder System, described by Nicolopoulos [18]. the assessment of the single limb balance with open and closed eyes in conjunction with the EMG activation time A combined stability parameter (σ ), described by Riley et measurements, under three conditions: i) without brace; al. [19], was also used for the overall balance assessment, ii) with brace and 30 kPa application pressure; and iii) which is based on the root mean square variance of both with brace and 60 kPa application pressure. A moderate the centre of pressure excursion and centre of pressure and a high application pressure were chosen because prac- excursion velocity in the anteropostreior and mediolateral tically, athletes apply ankle braces subjectively, according direction according to the formula: to the level of support and comfort they prefer. Comfort 2 2 means better performance and support better injury pre- σ = √σ + σ r AP r Latr r vention and the criterion for this choice lies with the indi- vidual so far, since no study exists to support any of these where: σ is the combined stability parameter; σ and r AP r parameters. Brace application pressure of 30 kPa resem- σ are the directional anteroposterior and mediolateral Latr r bles a moderately tightened brace and may be chosen by stability parameters correspondingly. some sports participants in order to be more comfortable and to not hinder their performance. On the other hand, The stability parameter was calculated in order to have a 60 kPa brace application resembles a highly tight applica- picture of the brace application on the total balance. Sub- tion with none of the subjects however reporting pain, jects were asked to stand on their dominant foot (which discomfort, discolouration or microcirculation distur- was determined by asking them to pretend to kick a ball, bances, in this study. This tight application may be chosen with the kicking leg being the dominant), for 5 seconds as by sports participants whose main concern is to prevent quietly as possible, staring at a 3 cm spot fixed one meter ankle injury or re-injury. Furthermore, 60 kPa application on the wall in front of them (Figure 1). Balance was meas- pressure is safe because it is significantly lower than the ured with open and closed eyes and a mean of two trials skin pressure threshold of 100 kPa which causes skin for each condition was calculated. The same procedure breakage [20]. Since ankle brace application pressures was repeated for all three ankle brace conditions. have not been measured by previous studies, this is a first attempt to apply pressures as close as possible to the com- Interface pressure was measured with the 9811 F-Socket monly used application techniques by sports participants, (Teckscan Inc., Boston, MA) sensor which was applied in for the above reasons. the anterior aspect of the ankle underlying the brace laces. The F-Socket was calibrated using a sphygmomanometer The laced-up McDavid ankle brace (McDavid Ankle around the ankle joint up to the point where the desired Guard Inc., Chicago, IL) was used for the measurements pressures (30 & 60 kPa) were reached. in the study. Pressure was applied by tightening the laces until the pre- Single limb balance assessment determined amount of pressure (30 & 60 kPa) was Single limb balance was assessed using the MatSCAN reached (Figure 2). The two pressures were chosen force platform (Tekscan Inc., Boston, MA) which dis- because according to Convery & Bui [20], any pressure of played the average centre of pressure (COP) excursion and 100 kPa and above can cause skin damage, therefore the centre of pressure excursion velocity in the anteroposte- higher pressure of 60 kPa was much below that level and rior and mediolateral directions. All measurements the 30 kPa was chosen as a moderate pressure. Further- described in the study were performed without shoes. All more, according to Meinders et al [21], pressures of 40 kPa measurements, in all subjects, were performed firstly and over can temporarily stop microcirculation but cause without brace, secondly with brace and 30 kpa pressure immediate hyperaemia immediately after pressure is and thirdly with brace and 60 kPa pressure. For this rea- removed. Since the brace was removed after each experi- son an order effect was ruled out, since it was the same for ment there was no incident of skin irritation or damage. Table 1: Demographic variables (N = 33) EMG measurements The effect of the McDavid ankle brace on the sequence of Age 21.5 ± 1.5 Weight (kgrs) 77.9 ± 8.9 lower limb EMG muscle activation was measured simulta- Height (cm) 177.5 ± 7.4 neously with the balance measurements. Surface Electro- BMI 24.8 ± 2.9 myography (EMG) was used to determine the activation Fat (%) 19.9 ± 4.1 time of the gastrocnemius, peroneous longus, rectus fem- Lean Body Mass 62.2 ± 6.1 oris and biceps femoris muscles, using a pair of bipolar Activity level 8.5 ± 1.5 surface silver chloride electrodes. These muscles were Page 3 of 8 (page number not for citation purposes) BMC Musculoskeletal Disorders 2007, 8:89 http://www.biomedcentral.com/1471-2474/8/89 Ski and 30 kPa (right) p Figure 2 n-ankle brace inte ressure applica rface pressure pattern for tion conditions 60 kPa (left) Skin-ankle brace interface pressure pattern for 60 kPa (left) and 30 kPa (right) pressure application conditions. between 20 and 500 Hz, in order to subtract electromag- netic noise, and movement artefacts were filtered with a high pass cut off frequency of 20 Hz [25]. The first visible signal that was 2 SDs above baseline activity was consid- ered as the onset of muscle activation [12,15,16]. Statistical analysis Statistical analysis was performed with the SPSS version 11.5. In order to analyze differences for balance and EMG measurements between the three ankle brace conditions, as well as for open and closed eyes and the eyes by brace interactions, the two way ANOVA was used. The Bonfer- onni test was applied for post-hoc comparisons in order to calculate the range of differences and the mean differ- Sing Figure 1 le limb balance and muscle activation measurement ences, together with the 95% confidence interval. The Single limb balance and muscle activation measurement. paired t-test and the mixed effects ANOVA model on the other hand were used to calculate differences for the sta- selected because according to the literature they have been bility parameter. Since balance was measured twice on the used by previous studies for the EMG measurement dur- same individual, once with open and another time with ing single limb balance and are of significant importance closed eyes, a paired t-test was used to calculate the differ- in the control strategy of standing balance [10,17]. ence in stability parameter between open and closed eyes. The Biopac MP100 System (BiopacSystems, Inc, Goleta, Similarly, as the balance for the 3 ankle brace conditions CA) was used to record and analyse the EMG signal. After was measured three times on the same individual, a mixed the skin was shaved and degreased with 70% alcoholic effects ANOVA model was used to calculate the differ- solution, electrodes were attached to the skin parallel to ences in the stability parameter between the three brace the muscle fibres, on the most prominent point of the conditions taking also into account the correlation muscles [22-24], during isometric contraction and palpa- between adjacent observations. For the assessing the sta- tion, according to the specifications by Perotto [24], and tistical significance of a hypothesis a common significance an interelectrode distance of 3 cm. Correct placement of level of 5% was assumed. the electrodes was tested for crosstalk by asking the sub- jects to perform active contractions of all four muscles that Results Single limb balance were measured. The ground electrodes ware placed on bony prominences of the knee and ankle. The raw EMG Mean values for the centre of pressure excursion (mm) signal was sampled by the computer with a frequency of and centre of pressure excursion velocity (mm/sec), in the 1000 Hz. Processing of the raw EMG signal was per- mediolateral and anteroposterior direction are displayed formed by converting it to RMS, band pass filtrered in Tables 2 and 3. No significant differences were found in Page 4 of 8 (page number not for citation purposes) BMC Musculoskeletal Disorders 2007, 8:89 http://www.biomedcentral.com/1471-2474/8/89 Table 3: Mean values for the anteroposterior sway and sway the mediolateral centre of pressure excursion and centre of velocity for three ankle brace conditions with open and closed pressure excursion velocity between the three ankle brace eyes (N = 33) conditions (F = 0.29, df = 2, p = 0.749) (Table 2). Anteropostreior sway Anteroposterior sway (mm) velocity (mm/sec) In the anteroposterior direction however, significant dif- ferences were found between the condition with 30 kPa Open eyes Closed Open eyes Closed brace application and the condition without brace (mean eyes eyes difference = 3.08, 95% CI: 0.06–6.1; p = 0.043) and between the condition with 60 kPa brace application and Ankle x ± SD x ± SD x ± SD x ± SD the condition without brace (mean difference = 3.09, 95% brace CI: 0.08–6.11; p = 0.042). Specifically, ankle brace appli- condition Without 14.8 ± 3.09 25.64 ± 118.06 ± 205.12 ± cation resulted in a deterioration of the anteroposterior brace 7.99** 24.08 63.9** COP excursion and excursion velocity, both with open With brace 15.39 ± 31.23 ± 123.15 ± 249.8 ± and closed eyes (Table 3). As far as the effect of vision is (30 kPa) 3.99 9.88** 31.9 79.02** concerned, significant differences were found between With brace 16.41 ± 30.24 ± 131.45 ± 241.88 ± open and closed eyes, both in the mediolateral (F = 22.3, (60 kPa) 4.44 10.1** 35.1 80.5** df = 1, 192, p < 0.001) and the anteroposterior (F = 175.4, ** F = 22.8, df = 1, p < 0.001 for the difference between open and df = 1, 192, p < 0.001) direction, in all three ankle brace closed eyes in Velocity application pressure conditions, with single limb balance being significantly worse with closed eyes. (Tables 2 and EMG Measurements 3). Analysis of variance showed that there were no significant differences in the activation time of the peroneus longus As far as the stability parameters are concerned, no signif- (F = 0.008, df = 2, p = 0.99), gastrocnemius (F = 0.28, df = icant differences were detected in single limb balance 2, p = 0.75), rectus femoris (F = 1.13, df = 2, p = 0.32) and between the three brace application conditions, in the biceps femoris (F = 2.11, df = 2, p = 0.124), between the anteroposterior (F = 2.12, df = 2, p = 0.13), mediolateral three ankle brace application conditions. Furthermore, no (F = 0.05, df = 2, p = 0.95) and the total (F = 0.26, df = 1, significant differences in EMG activation time were found p = 0.77) stability parameters. Lastly, significant differ- in single limb balance between open and closed eyes for ences were found in the total stability parameter between the peroneus longus, gastrocnemius and rectus femoris open and closed eyes (F = 2.24, df = 32, p = 0.032). Table muscles. However, significantly faster activation of the 4 displays the mean values and standard deviations of the biceps femoris muscle was detected with open eyes as stability parameters for the three ankle brace and eye con- compared to closed eyes, in all three brace conditions. ditions. Mean EMG activation time values are displayed in Table 5. No change in the EMG activation time sequence was observed for the four lower limb muascles that were tested in the three brace application conditions (Table 6). Table 2: Mean values for mediolateral sway and sway velocity for Discussion three ankle brace conditions with open and closed eyes (N = 33) To the best of our knowledge, this study is the first to investigate the effects of ankle brace application pressures Medioliateral sway Medioliateral sway (mm) velocity (mm/sec) on postural control and electromyographic activation sequence of lower limb muscles. In a recent study, Papa- Open eyes Closed Open eyes Closed Table 4: Mean values for the anteroposterior (σ ), mediolateral eyes eyes Apr (σ ) and total (σ ) stability parameters for open and closed eyes Latr r and the three ankle brace conditions (N = 33) Ankle x ± SD x ± SD x ± SD x ± SD brace Condition σ σ σ Apr Latr r condition Without 36.04 ± 52.8 ± 290.2 ± 423.6 ± Open eyes 21.83 ± 11.4 131.65 ± 103.3 136.41 ± 99.9 brace 23.2 28.0* 184.2 224.2* With brace 34.2 ± 22.7 48.5 ± 275.06 ± 401.0 ± Closed eyes 69.9 ± 39.5 152.17 ± 85.3 174.45 ± 79.87 (30 kPa) 21.2* 183.7 185.5* Without brace 65.84 ± 45.5 116.09 ± 119.3 145.2 ± 113.7 With brace 35.2 ± 23.8 50.9 ± 284.03 ± 407.4 ± With brace 30 92.68 ± 54.8 118.71 ± 90.12 162.5 ± 85.3 (60 kPa) 19.2* 188.8 153.6* kPa With brace 60 79.05 ± 54.8 124.08 ± 94.6 157.3 ± 93.7 kPa * F = 22.3, df = 1, p < 0.001 for the difference between open and closed eyes Page 5 of 8 (page number not for citation purposes) BMC Musculoskeletal Disorders 2007, 8:89 http://www.biomedcentral.com/1471-2474/8/89 Table 5: Mean EMG activation times (msec), of lower limb muscles, for the three ankle brace conditions with open (OE) and closed eyes (CE) (N = 33) Peroneous longous Gastrocnemius Rectus Femoris Biceps Femoris Ankle brace condition OE CE OE CE OE CE OE CE Without brace 31.7 ± 6.3 30.7 ± 6.4 33.06 ± 7.07 32.3 ± 6.4 117.06 ± 31.2 117.87 ± 35.9 118.5 ± 27.1 123.8 ± 34.7 With brace (30 kPa) 31.2 ± 5.2 31.1 ± 6.8 32.2 ± 5.4 31.5 ± 6.7 111.8 ± 22.1 125.1 ± 28.4 118.8 ± 26.4 143.1 ± 42.8 With brace (60 kPa) 31.6 ± 5.5 30.5 ± 6.3 32.5 ± 7.3 32.2 ± 6.1 127.8 ± 35.1 121.69 ± 26.2 119.2 ± 27.5 123.5 ± 25.4 dopoulos et al. [26], examined the effects of different posterior (σ ) stability parameters, as well as the total Latr ankle brace application pressures on the peroneus longus stability parameter (σ ), were not significantly affected, it reaction time, during a sudden inversion stress test and may be concluded that overall, the application of the two found that ankle brace application with medium and high different ankle brace application pressures, had no posi- pressure, resulted in a significant delay of the peroneal tive or negative effect on quiet single limb balance. This is reaction time. In the current study, we investigated the also supported by Riley et al. [7], who stated that the sta- effect of no brace application and two different ankle bility parameter they calculated, which combines both the brace application pressures, on single limb balance con- centre of pressure excursion and centre of pressure excur- trol and the electromyographic activation sequence of sion velocity, as well as the mediolateral and anteroposte- four lower limb muscles. The results showed that overall rior planes, is more valid and representative for the with the specific type of brace that was used in this study, assessment of standing balance than separately assessing postural control, as assessed by the total stability parame- each of these parameters alone. This information may be ter 'σ ', was not positively or adversely affected by the two useful in future studies as well as in the clinical setting, different brace application pressures. This finding is in since it seems that the application of the laced-up ankle agreement with previous studies, which showed that brace with a moderate and a high pressure, had no signif- ankle bracing had no effect on postural control, without icant stimulation effect on the peripheral, mainly skin however, referring to the pressure of brace application receptors, and therefore afferent signals were not strong [5,6]. It was also shown that different ankle brace applica- enough to provoke a specific central response and affect tion pressures had no effect on the mediolateral plane but single limb balance control. Another finding of this study on the other hand, it significantly deteriorated balance in was that single limb balance was significantly worse with the anteroposterior plane. These findings are partly in closed eyes as compared to open eyes. This is in agreement agreement with Bennell & Goldie [1], and Papadopoulos with previous studies [2,28-31] and further establishes the et al. [2], who also found that ankle bracing adversely importance of vision which is one of the three major affected balance in young healthy volunteers. However, sources of balance control together with the vestibular sys- the fact that mediolateral balance was not affected in any tem and the peripheral joint receptors [32]. of the three brace application conditions may be more valid in this research since in this study sample, the COP The results of the electromyographic measurements trajectory during single limb balance, mainly traveled in showed that the sequence of lower limb muscle activation the mediolateral direction. The deterioration of balance in onset was not altered by the application of two different the anteroposterior direction may also be attributed to the ankle brace application pressures. This finding cannot be fact that muscular control of single limb balance which is compared with previous studies since this is the only more efficient in the AP direction [27], was adversely study that has investigated the effect of ankle bracing on affected by the application of the ankle brace. Further- the EMG activity of lower limb muscles and, as mentioned more, since both the mediolateral (σ ) and the antero- above, the only that has examined the effect of different Apr Table 6: EMG activation sequence of lower limb muscles during single limb balance in the three brace application conditions Brace condition EYES Peroneus longus Gastrocnemius Rectus femoris Biceps femoris Without brace Open 1 2 3 4 Closed 1 2 3 4 With brace (30 kPa) Open 1 2 3 4 Closed 1 2 3 4 With brace (60 kPa) Open 1 2 4 3 Closed 1 2 3 4 Page 6 of 8 (page number not for citation purposes) BMC Musculoskeletal Disorders 2007, 8:89 http://www.biomedcentral.com/1471-2474/8/89 brace application pressures. However, useful information Competing interests that arises is that different ankle brace application pres- The authors declare that they have no competing interests. sures do not change the ankle strategy of balance control, which is the one that dominates during balance of young Authors' contributions healthy subjects [15,10,14,9,33]. Therefore, the fact that ESP, CN, and AB participated in the design of the study, the more distal peroneus longus and gastrocnemius mus- data acquisition and analysis and writing of this manu- cles were activated faster than the more proximal thigh script. GV, participated in the analysis and writing of this muscles (rectus femoris and biceps femoris), both in the paper. SAP and SA participated in the analysis and also in condition without brace and the conditions with moder- revising critically the manuscript. All authors read and ate and high brace application pressures, further supports approved the final manuscript. the hypothesis that the central nervous system (CNS) does not alter its single limb balance control strategy. Several Acknowledgements The authors wish to thank Mr. Vasilios Nikolaou for his contribution to the explanations may be given for this observation: first, the statistical analysis of this study. skin receptors are either not adequately stimulated by the high application pressure of the brace so as, in turn, to References provoke a CNS response, or their role in controlling single 1. Bennell KL, Goldie PA: The differential effects of external ankle limb balance is less important. Second, the fact that the support on postural control. J Orthop Sport Phys Ther 1994, study sample consisted of non-injured subjects, may in 20(6):287-295. 2. Papadopoulos E, Karzis K, Tsakoniti K, Karteroliotis K, Athanasopo- part explain the lack of pressure application effect on bal- ulos S: The immediate effect of ankle bracing, head extension ance. It could be argued that joint receptors in healthy and vision on single limb balance. Proceedings of the 7th Congress of the European College of Sport Science: 24–28 July 2002; Athens subjects may be adequate in preventing single balance dis- 2002:868. tortion with different ankle brace application pressures. 3. Baier M, Hopf T: Ankle orthoses effect on single-limb standing However, this is not supported by previous studies since balance in athletes with functional ankle instability. Arch Phys Med Rehab 1998, 79:939-944. ligament receptors are stimulated in the end ranges of 4. Feuerbach JW, Grabiner MD: Effect of the aircast on unilateral joint motion and therefore ligament injury affects only postural control: amplitude and frequency variables. J Orthop Sport Phys Ther 1993, 17(3):149-154. the mechanical and not the functional dynamic stability 5. Friden T, Zatterstrom R, Moritz U: A stabilometric technique for of the joint which is mostly controlled by the muscle spin- evaluation of lower limb instabilities. Am J Sport Med 1989, dles [32]. Further research, which will investigate the 17:118-122. 6. Palmieri RM, Ingersoll CD, Cordova ST, Kinzey SJ: The spectral effect of ankle brace application in injured subjects too, is qualities of postural control are unaffected by 4 days of necessary. ankle-brace application. J Athl Training 2002, 37(3):269-274. 7. Roller SJ, Livengood AL, Mattacola CG, Uhl TL, Malone TR: Effect of prophylactic ankle bracing on postural control and EMG of Conclusion lower extremity and trunk muscles. Journal of Athletic Training The findings of this study showed that regardless of appli- 2003, 38(2):S-89. 8. 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Yaggie JA, McGregor SJ: Effects of isokinetic ankle fatigue on the maintenance of balance and postural limits. Arch Phys Med Rehab 2002, 83:224-228. Pre-publication history The pre-publication history for this paper can be accessed here: http://www.biomedcentral.com/1471-2474/8/89/prepub Publish with Bio Med Central and every scientist can read your work free of charge "BioMed Central will be the most significant development for disseminating the results of biomedical researc h in our lifetime." Sir Paul Nurse, Cancer Research UK Your research papers will be: available free of charge to the entire biomedical community peer reviewed and published immediately upon acceptance cited in PubMed and archived on PubMed Central yours — you keep the copyright BioMedcentral Submit your manuscript here: http://www.biomedcentral.com/info/publishing_adv.asp Page 8 of 8 (page number not for citation purposes)

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