Ankle injuries, especially lateral ankle sprains, are some of the

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1 GULCAN HARPUT, PT, MSc 1 A. RUHI SOYLU, MD, PhD 2 HAYRI ERTAN, PhD 3 NEVIN ERGUN, PT, PhD 1 Activation of Selected Ankle Muscles During Exercises Performed on Rigid and Compliant Balance Platforms Ankle injuries, especially lateral ankle sprains, are some of the most common injuries in sports 13 and can also occur during performance of regular daily activities. 5,12 Consequently, a variety of balance platforms are often used as part of an intervention program, with the aim of enhancing joint stability by increasing the demands of ankle muscles to decrease the incidence of or to treat ankle injuries. 1,11,14 However, there is very little information in the literature to help clinicians stage the progression of a program based on the relative muscular demands required from various. 1,4,17 It is our impression that most clinicians consider the performance of TTSTUDY DESIGN: Experimental laboratory study. TTOBJECTIVE: To compare how the design of 2 balance platforms affects ankle musculature activation for various weight-bearing exercises. TTBACKGROUND: Balance platforms are widely used in both training and rehabilitation, and a better understanding of how platform design and type of exercise modify the demands on the ankle musculature may be helpful in staging exercise progression. TTMETHODS: Surface electromyography was used to measure the activation level of the fibularis longus, tibialis anterior, and medial gastrocnemius while performing 4 exercises on 2 different balance platforms (compliant and rigid). Twenty-four (12 females, 12 males) healthy, sedentary subjects participated in the study. Analysis of variance was balance exercises on a balance platform with a compliant surface to be more difficult than performing the same exercise on a platform with a rigid surface. The aim of this study was to quantify and compare the level of activation of the used for statistical analysis. TTRESULTS: There was no significant interaction between (P>.5), and the type of platform did not influence muscle activation for the 3 muscles monitored (P>.5). The highest activation level for the fibularis longus and medial gastrocnemius was obtained during single-leg stance, and for the tibialis anterior during the single-leg squat (P<.5). TTCONCLUSION: In this study, although the demands on the ankle musculature were similar for selected exercises performed on a compliant versus a rigid balance platform, muscle activation level varied based on the exercise. J Orthop Sports Phys Ther 13;43(8): Epub 11 June 13. doi:1.2519/jospt TTKEY WORDS: electromyography, EMG, posture fibularis longus (FL), tibialis anterior (TA), and medial gastrocnemius (mgc) muscles during the performance of 4 exercises on 2 types of balance platforms. It was hypothesized that exercises performed on a compliant platform would require greater muscle activation than those performed on a rigid platform. METHODS Subjects Twenty-four healthy sedentary subjects (12 females [mean SD age, years; weight, kg; height, cm] and 12 males [age, years; weight, kg; height, cm]), without a history of lower extremity injuries or systemic or neurologic disorders, volunteered to participate in this study. The data from 1 subject were not included in the statistical analysis due to missing data secondary to hardware malfunction. Sedentary was defined as a lack of participation in sport activities. The Local Ethics Committee of Hacettepe University approved the protocol for the study. All participants provided informed consent prior to study enrollment. Electromyographic (EMG) System Bipolar Ag/AgCl surface electrodes, with 1 Department of Physiotherapy and Rehabilitation, Faculty of Health Sciences, Hacettepe University, Ankara, Turkey. 2 Department of Biophysics, Faculty of Medicine, Hacettepe University, Ankara, Turkey. 3 School of Physical Education and Sports, Anadolu University, Eskisehir, Turkey. The Local Ethics Committee of Hacettepe University approved the protocol for this study. This study was supported by Thera-Band (The Hygenic Corporation), which provided the Wobble Boards, and Anadolu University, which provided the electromyographic system (Project ANADOLU UNI/BAP 11S). Address correspondence to Gulcan Harput, Hacettepe University, Faculty of Health Sciences, Department of Physiotherapy and Rehabilitation, Sihhiye 61 Ankara, Turkey. aktasgulcan@yahoo.com; gulcan.aktas@hacettepe.edu.tr t Copyright 13 Journal of Orthopaedic & Sports Physical Therapy journal of orthopaedic & sports physical therapy volume 43 number 8 august

2 an interelectrode distance of 1 cm, were used to record the EMG signal of the FL, TA, and mgc (Myomonitor system; Delsys Inc, Boston, MA). The sampling rate was 1 Hz, the signal was amplified 1 times, the common-mode rejection ratio was greater than 8 db, and the input impedance was greater than 1 MΩ. Consistent with published recommendations, 15 the electrodes for the FL muscle were positioned 25% of the distance between the tip of the head of the fibula and the tip of the lateral malleolus. For the TA muscle, the electrodes were positioned one third of the distance between the tip of the head of the fibula and the tip of the medial malleolus. For the mgc, the electrodes were located on the midsection of the medial part of the muscle. To minimize skin impedance, the hair where the electrodes were located was shaved and the skin was subsequently cleaned with 7% isopropyl alcohol. 7 For testing, the electrodes were firmly secured with athletic tape to prevent movement. Maximum Voluntary Isometric Contractions Prior to performance of the exercises, and for the purpose of normalization, EMG data were collected for each of the muscles while performing maximum voluntary isometric contractions (MV- ICs). With the subject in a long-sitting position, the examiner manually resisted a maximum effort, combining ankle dorsiflexion and inversion for the TA and combining plantar flexion and eversion for the FL. For the mgc, the rigid arm of an isokinetic device locked in a neutral position was used to resist ankle plantar flexion. After a practice trial, each muscle was tested 3 times, each trial lasting 5 seconds, with a 2-minute interval between trials. Standardized verbal encouragements were provided during testing. Exercises and Balance Platforms After preparation of the subjects for EMG data collection and completion of FIGURE 1. (A) Forward lunge exercise performed on compliant balance platform. (B) Side lunge exercise performed on rigid balance platform. (C) Single-leg stance exercise performed on compliant balance platform. (D) Single-leg squat exercise performed on rigid balance platform. testing for MVICs, all participants performed 4 exercises on 2 different balance platforms. The order of presentation of the platforms was randomized, as well as the order for performing the 4 exercises. Forward Lunge and Side Lunge The forward lunge and side lunge exercises were performed with the foot of the dominant limb on the balance platform. The knee flexion angle of the tested limb was standardized at, and the participant was instructed to keep the trunk upright and transfer near full body weight to the dominant limb while straightening the opposite lower limb (FIGURE 1A and 1B). The dominant limb was defined as the preferred limb to kick a ball. Single-Leg Stance With eyes open, the subjects were instructed to stand on their dominant limb, with their knee held near full extension. The knee of the opposite limb was held in a semi-flexed position (FIGURE 1C). Single-Leg Squat The subjects kept their balance while maintaining a single-leg squat position on their dominant limb, with the knee in 45 of flexion (FIGURE 1D). Balance Platforms Two balance platforms were used in this study: a compliant platform (BOSU; BOSU Fitness, LLC, San Diego, CA) and a rigid platform (Thera-Band Wobble Board; The Hygenic Corporation, Akron, OH). The compliant platform provided a stable interface between the 556 august 13 volume 43 number 8 journal of orthopaedic & sports physical therapy

3 TABLE 1 platform and the floor, with the subject standing on a semi-compliant surface. In contrast, the rigid platform provided a firm interface between the foot and the platform but an unstable surface between the floor and the platform. Descriptive Statistics for Muscle Activation Level for 4 Exercises Performed on 2 Balance Platforms* Muscle/Exercise Compliant Surface Rigid Surface Fibularis longus Forward lunge (5.9, 1.5) (8.1, 13.1) Side lunge (7., 12.9) (8., 12.3) Single-leg stance (41.4, 59.6) (39.7, 54.8) Single-leg squat (27.3, 39.9) (25., 35.4) Tibialis anterior Forward lunge (7.9, 21.8) (8., 16.1) Side lunge (14.9, 28.5) (17.6, 32.7) Single-leg stance (13.3, 21.8) (1.6, 17.7) Single-leg squat (.3, 36.) (18.5, 33.7) Medial gastrocnemius Forward lunge (3.6, 6.9) (4.6, 7.9) Side lunge (3.1, 5.1) (3.1, 5.8) Single-leg stance (27.7, 48.5) (27.2, 43.4) Single-leg squat (13.1, 21.2) (9.7, 17.7) *n = 23. Values are mean SD (95% confidence interval) percent maximum voluntary isometric contraction. TABLE 2 Forward lunge Intrarater Reliability for Muscle Activation* Compliant Rigid Compliant Rigid Compliant Rigid SEM Side lunge SEM Single-leg stance SEM Single-leg squat Fibularis Longus Tibialis Anterior Medial Gastrocnemius SEM Abbreviations: ICC, intraclass correlation coefficient; SEM, standard error of measurement. *n = 23. Values are percent maximum voluntary isometric contraction. Testing Procedures A foot switch located under the first metatarsal of the tested limb was used to trigger EMG recording when the foot made contact with the balance platform. For each exercise, the subject performed 3 trials, with each trial held for 15 seconds. Two minutes of rest was provided between each exercise. During each exercise, visual observation was used to try to standardize overall body position. Any trial for which excessive movement of the trunk or loss of balance occurred was stopped and repeated. Knee flexion angle, at for the 2 lunge exercises and at 45 for the single-leg squat exercise, was monitored with an electrogoniometer, and the subjects were verbally informed during testing when the knee flexion angle deviated from the desired position. EMG Signal Processing EMG data processing was done using MATLAB Version R12a (The Math- Works, Inc, Natick, MA). The EMG signals were band-pass filtered (-45 Hz) and smoothed using a root-mean-square and a 1-millisecond moving-window function. For each of the MVIC trials, the maximum value obtained over the 5-second maximum effort was recorded, and the trial with the maximum value was used for normalization of the EMG data obtained during the exercises. For each of the 3 trials of each exercise, the maximum signal amplitude of the middle 5 seconds of the 15-second data-collection period for each muscle was divided by its corresponding MVIC value. Then, the average of the 3 trials, expressed as a percentage of MVIC, was used for data analysis. Statistical Analysis SPSS Version 15. (SPSS Inc, Chicago, IL) was used for all statistical analyses. Intraclass correlation coefficients (model 3,1) and standard errors of measurement for the maximum EMG signal amplitude for the 3 repetitions of each exercise were used to determine reliability. Three separate (1 for each muscle) 2-way (platform by exercise), repeated-measures analyses of variance were used for data analysis. Paired-samples t tests were used for post hoc analysis. Given the descriptive nature of the study, the level of significance was maintained at P<.5. journal of orthopaedic & sports physical therapy volume 43 number 8 august

4 A B C 8 RESULTS TABLE 1 provides descriptive statistics (means, standard deviations, and 95% confidence intervals) for maximum muscle activation level expressed as a percentage of MVIC for the FL, TA, and mgc for each exercise and balance-platform combination. Intraclass correlation coefficients (model 3,1) for all combinations of exercise and platform ranged from.63 to.97, with corresponding standard errors of measurement ranging from.3% to 6.3% MVIC (TABLE 2). Fibularis Longus = 1.12, P =.34) and no significant =.3, P =.59). The main effect of exercise was significant = 86.1, P<.1), with post hoc testing revealing that the FL muscle was more active during the single-leg stance than during any other exercises (P<.1). In addition, the FL was more active during single-leg squat than during the forward lunge (P<.1) and side lunge (P<.1) exercises. Tibialis Anterior =.84, P =.57) and no significant =.17, P = 8 8 Platform 1 Platform 2.68). The main effect of exercise was significant = 6.34, P =.1), with the TA being more active during the singleleg squat compared to single-leg stance (P =.5) and the forward lunge (P =.1). Moreover, the TA was more active during the side lunge compared to the forward lunge exercise (P =.3). Medial Gastrocnemius = 1., P =.19) and no significant = 1., P =.26). The main effect of exercise was significant = 51.2, P<.1), with the mgc being more active during single-leg stance compared to all other exercises (P<.1). In addition, the mgc was more active during the single-leg squat when compared to the forward (P<.1) and side lunge (P<.1) exercises. DISCUSSION FIGURE 2. Ankle muscle activation levels during 4 exercises performed on 2 balance platforms. (A) Fibularis longus, (B) tibialis anterior, (C) medial gastrocnemius. Values are mean ± SD percent maximum voluntary isometric contraction. Abbreviations: FL, forward lunge; Platform 1, compliant surface; Platform 2, rigid surface; SL, side lunge; SLSQ, single-leg squat; SLST, single-leg stance. The main purpose of this study was to quantify and compare the level of activation of the FL, TA, and mgc muscles for 4 exercises performed on 2 types of balance platform. The results showed that the design of the balance platform (rigid versus compliant surface) did not influence the activation level of the muscles monitored during the forward lunge and side lunge exercises and during the single-leg stance and single-leg squat exercises performed by healthy, sedentary subjects. Previous studies indicated that the level of muscle activation of the ankle musculature during a single-leg stance exercise was greater when performed on balance boards than when performed on flat ground. 1,4 Similar to our results, Braun Ferreira et al 3 determined that there was no difference in muscle activation of the TA, tibialis posterior, FL, and gastrocnemius muscles during a single-leg stance performed on a trampoline versus a balance board. Conversely, Blackburn et al 1 reported a greater EMG signal amplitude for the FL, TA, soleus, and gastrocnemius muscles when performing a single-leg stance exercise on a rigid platform compared to soft surfaces. In our study, the ankle was in a static position during the exercises performed on 2 different platforms, causing the level of ankle muscle activation to be low. This low level of muscle activation might not have been sufficient to create a difference between these 2 different balance platforms. As would be expected, the activation level of the ankle musculature for healthy individuals with normal muscle strength was relatively low for the 2 lunge exercises. The more proximal knee and hip musculatures could act as the primary stabilizers during these exercises. 8,1 Therefore, these exercises may be useful in the earlier stages of ankle rehabilitation or training, especially in individuals who may have relative weakness of the ankle musculature following an injury or surgery. There was greater activation of both the FL and mgc muscles during the single-leg stance versus the single-leg squat exercise, which is in contrast to the findings for the TA (FIGURE 2). This greater recruitment of both plantar flexors during the single-leg stance exercise is consistent with a strategy to keep the line of gravity in the sagittal plane slightly anterior to the axis of rotation of the ankle to maintain balance during stance. 2,16,18 The greater relative activation of the TA and lesser activation of the plantar flexors during the single-leg squat exercise may reflect a more posterior location 558 august 13 volume 43 number 8 journal of orthopaedic & sports physical therapy

5 of the center of mass during this exercise, which requires hip and knee flexion. In addition, during this exercise, the TA muscle may be actively engaged in maintaining the desired dorsiflexed position of the ankle. 6,9 One potential limitation of this study, which may be reflected in the relatively large standard deviations of the EMG data, is that, with the exception of the knee angle, monitoring of subject position during the exercises was performed through visual inspection. CONCLUSION There was no difference in muscle activation of the FL, TA, and mgc when comparing 4 exercises performed on a compliant versus a rigid balance platform. The 4 exercises required a varied amount of muscle activation, with the TA being most active during the single-leg squat, and the FL and mgc during the single-leg stance. t ACKNOWLEDGEMENTS: The authors would like to thank Cigdem Okcu and Harun Harput for their assistance. REFERENCES 1. Blackburn JT, Hirth CJ, Guskiewicz KM. Exercise sandals increase lower extremity electromyographic activity during functional activities. J Athl Train. 3;38: Borg F, Finell M, Hakala I, Herrala M. Analyzing gastrocnemius EMG-activity and sway data from quiet and perturbed standing. J Electromyogr Kinesiol. 7;17: jelekin Braun Ferreira LA, Pereira WM, Rossi LP, Kerpers II, Rodrigues de Paula A, Jr., Oliveira CS. Analysis of electromyographic activity of ankle muscles on stable and unstable surfaces with eyes open and closed. J Bodyw Mov Ther. 11;15: org/1.116/j.jbmt Cordova ML, Jutte LS, Hopkins JT. EMG comparison of selected ankle rehabilitation exercises. J Sport Rehabil. 1999;8: Croy T, Saliba SA, Saliba E, Anderson MW, Hertel J. Differences in lateral ankle laxity measured via stress ultrasonography in individuals with chronic ankle instability, ankle sprain copers, and healthy individuals. J Orthop Sports Phys Ther. 12;42: Dan B, Bouillot E, Bengoetxea A, Noël P, Kahn A, Cheron G. Adaptive motor strategy for squatting in spastic diplegia. Eur J Paediatr Neurol. 1999;3: De Luca CJ. The use of surface electromyography in biomechanics. J Appl Biomech. 1997;13: Ekstrom RA, Donatelli RA, Carp KC. Electromyographic analysis of core trunk, hip, and thigh muscles during 9 rehabilitation exercises. J Orthop Sports Phys Ther. 7;37: jospt Escamilla RF. Knee biomechanics of the dynamic squat exercise. Med Sci Sports Exerc. 1;33: Irish SE, Millward AJ, Wride J, Haas BM, Shum GL. The effect of closed-kinetic chain exercises and open-kinetic chain exercise on the muscle activity of vastus medialis oblique and vastus lateralis. J Strength Cond Res. 1;24: NOTIFY JOSPT of Changes in Address JSC.b13e3181cf749f 11. Laudner KG, Koschnitzky MM. Ankle muscle activation when using the Both Sides Utilized (BOSU) balance trainer. J Strength Cond Res. 1;24: JSC.b13e3181c49d4 12. Leanderson J, Eriksson E, Nilsson C, Wykman A. Proprioception in classical ballet dancers. A prospective study of the influence of an ankle sprain on proprioception in the ankle joint. Am J Sports Med. 1996;24: Linford CW, Hopkins JT, Schulthies SS, Freland B, Draper DO, Hunter I. Effects of neuromuscular training on the reaction time and electromechanical delay of the peroneus longus muscle. Arch Phys Med Rehabil. 6;87: apmr McGuine TA, Keene JS. The effect of a balance training program on the risk of ankle sprains in high school athletes. Am J Sports Med. 6;34: org/1.1177/ Merletti R, Hermens H. Introduction to the special issue on the SENIAM European Concerted Action. J Electromyogr Kinesiol. ;1: Rodgers MM. Dynamic biomechanics of the normal foot and ankle during walking and running. Phys Ther. 1988;68: Soderberg GL, Cook TM, Rider SC, Stephenitch BL. Electromyographic activity of selected leg musculature in subjects with normal and chronically sprained ankles performing on a BAPS board. Phys Ther. 1991;71: Winter DA, Patla AE, Rietdyk S, Ishac MG. Ankle muscle stiffness in the control of balance during quiet standing. J Neurophysiol. MORE INFORMATION Please remember to let JOSPT know about changes in your mailing address. The US Postal Service typically will not forward second-class periodical mail. Journals are destroyed, and the USPS charges JOSPT for sending them to the wrong address. You may change your address online at Visit INFORMATION FOR READERS, click Change of Address, and select and complete the online form. We appreciate your assistance in keeping JOSPT s mailing list up to date. journal of orthopaedic & sports physical therapy volume 43 number 8 august

lntertester and lntratester Reliability of a Dynamic Balance Protocol Using the Biodex Stability System

Journal of Sport Rehabilitation, 1998, 7, 95-101 0 1998 Human Kinetics Publishers, Inc. lntertester and lntratester Reliability of a Dynamic Balance Protocol Using the Biodex Stability System Randy Schmitz