Author's response to reviews

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1 Author's response to reviews Title: The effect of different skin-ankle brace application pressures on quiet single-limb balance and electromyographic activation onset of lower limp muscles. Authors: Emmanouel S Papadopoulos (epapadop@phed.uoa.gr) Christos Nikolopoulos (orthofoo@cytanet.com.cy) Athanasios Badekas (thanosb@con.gr) George Vagenas (gvagenas@cc.uoa.gr) Stamatios A Papadakis (snapmd@in.gr) Spyros Athanasopoulos (spathana@phed.uoa.gr) Version: 2 Date: 29 October 2006 see over Author's response to reviews:

2 To the Editorial Board BMC Musculoskeletal Disorders Athens, October 28, 2006 RE: MS Dear Sir, Thank you very much for your regarding our manuscript entitled The effect of different skin-ankle brace application pressures on quiet single-limb balance and electromyographic activation onset of lower limp muscles. We have revised the manuscript according to the reviewers' suggestions. More specifically: Reviewer 1: Sandi Spaulding General We agree that further work is needed with the application of other types of ankle braces including the rigid ones in more real functional sports related activities, in order to see if their increased restricting effect (shown in previous studies), interfere with function and performance. This will be added at the conclusions section. Minor Essential Revisions The term 'center of pressure excursion' will be added in the text to replace sway.

3 Reviewer 2: Riann M Palmieri-Smith Major Compulsory Revisions Methods 1. Subjects never used of ankle brace or ankle support 2. Condition order was counterbalanced 3. Subjects performed all conditions on the same day with 30 minutes interval between conditions to avoid learning effect 4. Subject performed practice trials to become familiar with the experiments 5. Touchdown trials were disqualified and re-performed 6. We used Average COP sway 7. This is a typing error, we must add the squares ( 2 ) in the explaining terms and the v represents the square root but does not appear in the equation 8. Baseline muscle activity was recorded with the subjects in relaxed sitting position 9. i. Ankle brace: McDavid Ankle Guard Inc., Chicago, IL; ii. Pressure sensor: F-SOCKET (ekscan Inc., Boston, MA); iii. Balance platform: MaTScan System (ekscan Inc., Boston, MA); iv. EMG device: PAC MP100 (BIOPAC Systems, Inc. Goleta, CA) 10.These procedures were used for all four muscles that were tested 11.Interface pressure was measured with the 9811 F-Socket (Teckscan Inc., Boston, MA) sensor which was applied in the anterior aspect of the ankle underlying the brace laces. Pressure was applied by tightening the laces until the predetermined amount of pressure (30 & 60 kpa) was reached. The two pressures were chosen because according to Convery & Bui (1999), any pressure of 100 kpa and

4 above can cause skin damage, therefore the higher pressure of 60 kpa was much below that level and the 30 kpa was chosen as a moderate pressure. Furthermore, according to Meinders et al, pressures of 40 kpa and over can temporarily stop microcirculation but cause immediate hyperaemia immediately after pressure is removed. Since the brace was removed after each experiment there was no incident of skin irritation or damage. 12. by brace interactions 13.Bonferroni post-hoc comparisons are calculated for pair-wise group differences, once an overall significant group effect has been found. The way of calculating the mean difference for each pair of groups alongside with their 95% confidence intervals is made through the Statistical Package for Social Sciences (SPSS). 14.At a first place, a two-way ANOVA, i.e. an ANOVA with two independent variables Brace and Eyes with 3 (0, 30, 60) and 2 (open and closed) levels respectively was used to assess: The Brace main effect, i.e. differences in balance and EMG measurements between the 3 ankle conditions. The Eyes main effect, i.e. differences in balance and EMG measurements between open and closed eyes. The Brace by Eyes interactions, i.e. whether the differences in balance and EMG measurements between the 3 ankle conditions depend on the difference between open and closed eyes or vice versa, i.e. whether differences between open and closed eyes depend on differences between the 3 ankle conditions.

5 The paired t-test and the mixed effects ANOVA model on the other hand were used to calculate differences for the stability parameter. Since balance was measured twice on the same individual, once with open and another time with closed eyes, a paired t-test was used to calculate the difference in stability parameter between open and closed eyes. Similarly, as the balance for the 3 ankle brace conditions was measured three times on the same individual, a mixed effects ANOVA model was used to calculate the differences in the stability parameter between the three brace conditions taking also into account the correlation between adjacent observations. 15. For the assessing the statistical significance of a hypothesis a common significance level of 5% was assumed Results 1. Yes. Differences were calculated a) between the condition with 30 kpa ankle brace pressure application and the condition without brace and b) between the condition with 60 kpa ankle brace pressure application and the condition without brace. 2. This correct. So it will be:...both in the mediolateral (F = 22.3, df = 1, 192, p < 0.001) and the anteroposterior (F = 175.4, df = 1, 192, p < 0.001) direction, in all three ankle brace application pressure conditions, with single limb balance being significantly worse with closed eyes. 3. This is defined earlier in the stability parameter equation where the total stability parameter is calculated by the mediolateral and anteroposterior stability parameters

6 Minor Essential Revisions Background 1. You are right on this because we should be more specific and we apologize. That comment refers mainly to the study by Friden et al, (1989). What we meant to say, by stating technique of brace application (as with other similar studies) is that no information was provided as to the determination of the pressure that the brace applied onto the subjects. It will be rephrased in the text. 2. Lower limb activation sequence during standing balance is an important parameter which is related to ankle joint neuromuscular function. Specifically, it was considered important in this study to investigate whether the application of an ankle brace with different pressures affects only the activation sequence of four muscles, and not the overall EMG activity during the 5 sec trial, either due to the stimulation of the skin receptors or to the restriction of joint motion. In a previous study, Roller et al (2003) investigated the role of a semirigid ankle brace in the mediolateral and anteroposterior single limb balance, as well as the activation sequence of four lower limb muscles and the abdominal and low back muscles. he results showed no significant difference in AP and ML balance ability and EMG activation time between the conditions with and without brace, which is in agreement with the findings of the current study. In another study by Rose et al (2002), it was found that the application of semirigid orthotic ankle support did not affect the sequence of four knee muscles during dynamic single limb balance in subjects with overpronation of the foot. These are the only studies that have investigated the role of ankle bracing in lower limb muscles activation

7 sequence, and therefore further research is needed. The importance of studying muscle activation onset during a balance task has been demonstrated by several studies (Riemann et al, 2003; Gatev et al, 1999; Carpenter et al, 2001;) which described the different strategies used by a person to maintain an upright posture during static (Riemann et al, 2003; Gatev et al, 1999) or dynamic balance tasks (Henry et al, 1998; Gilles et al 1999; King & Zatsiorski, 2002; Bloem et al, 2000; Bloem et al, 2002; Allum et al, 2001) both in healthy and in individuals with proprioception deficit. The purpose of the current study was to examine whether the balance maintenance strategies during a single limb stance, can be altered with the application of a specific widely used type of ankle brace. Discussion 16. It will be removed and rephrased 17. The deterioration of balance in the anteroposterior direction may be attributed to the fact that muscular control of single limb balance which is more efficient in the AP direction (Loram et al, 2005), was adversely affected by the application of the ankle brace. 18. A possible explanation for the quicker activation of the biceps femoris with open eyes in the 60 kpa brace application pressure could be that high application pressure may lead to an alteration of the knee muscles activation sequence. However, this cannot be proved in this study and needs to be further investigated. The main finding of this study was that the more distal ankle muscles were activated faster in all brace conditions than the more proximal thigh muscles. Therefore, the ankle strategy of postural control during quiet stance was not altered in any of the three conditions tested.

8 Reviewer 3: John Nyland General i. It was the kicking leg. ii. These muscles were selected because according to the literature they have been used by previous studies for the EMG measurement during single limb balance and are of significant importance in the control strategy of standing balance (llum et al., 2001; Gatev et al., 1999). Major Compulsory Revisions i. All subjects provided a signed informed consent, and the proposal was approved by the University of Athens review board ii. This was a typing error and will be appropriately corrected (the square root appears as a v and 2 squares ( 2 ) are missing) iii. Baseline muscle activity was recorded with the subjects in relaxed sitting position iv. EMG and Balance measurement data collection was initiated when the subjects assumed the correct one-legged standing position. The first EMG signal that was equal or above 2 SDs above baseline was recorded for each muscle as the activation onset. v. All measurements described in the study were performed without shoes. The same measurements were carried out with shoes in a later study, not submitted for publication yet. The Tekscan mat calibration was done using a Uniform Bladder System, described by Nicolopoulos C, 2002 (MSc Podiatry Thesis University of Northampton) vi. This statement refers to the specific type of brace used in the study and refers to the finding of another study which showed that its application delayed the activation onset of the peroneous longus

9 during a simulated ankle sprain (sudden inversion). Of course futher study is needed before it can be generalized vii.it will be appropriately corrected in the text. viii.interface pressure was measured with the 9811 F-Socket (Teckscan Inc., Boston, MA) sensor which was applied in the anterior aspect of the ankle underlying the brace laces. Pressure was applied by tightening the laces until the predetermined amount of pressure (30 & 60 kpa) was reached. The two pressures were chosen because according to Convery & Bui (1999), any pressure of 100 kpa and above can cause skin damage, therefore the higher pressure of 60 kpa was much below that level and the 30 kpa was chosen as a moderate pressure. Furthermore, according to Meinders et al, pressures of 40 kpa and over can temporarily stop microcirculation but cause immediate hyperaemia immediately after pressure is removed. Since the brace was removed after each experiment there was no incident of skin irritation or damage. A native English-speaking colleague copyedited the paper, and eleven more references have been added. The authors thank you and the reviewers for the important recommendations for improving this manuscript. Sincerely yours, Stamatios A. Papadakis, MD, DSc Consultant Orthopaedic Surgeon