Wavelet analysis based on time–frequency information discriminate chronic ankle instability A. Martínez-Ramírez a , P. Lecumberri a , M. Gómez a , M. Izquierdo b, * a Mathematics Department, Public University of Navarra, Pamplona, Navarre, Spain b Studies, Research and Sports Medicine Center, Government of Navarra, Pamplona, Navarre, Spain article info Article history: Received 23 September 2009 Accepted 12 November 2009 Available online xxxx Keywords: Ankle sprains Dynamic balance Star Excursion Balance Test Accelerometer Gyroscope abstract Background: Ankle sprains are one of the most common lower extremity injuries. Real time human motion tracking is an accurate, inexpensive and portable system to obtain kinematic and kinetic mea- surements. The purpose of this study was to discriminate between subjects with chronic ankle instability and subjects with stable ankles through inertial tracking technology and force plates. Methods: Twelve subjects (mean (SD) 23.16 (5.32) years, 174.83 (8.78) cm, 73.58 (17.10) kg) with stable ankles and 13 (mean (SD) 24.69 (5.91) years, 173.31 (9.07) cm, 69.61 (15.32) kg) with chronic ankle insta- bility performed the Star Excursion Balance Test. Time–frequency information based on wavelet decom- position was used for analysing all signals. Findings: Dynamic balance impairment associated with chronic ankle instability was observed in the peak amplitude in the wavelet approximation as well as the absolute sum of the coefficients of the wave- let details of the acceleration, orientation and force signals. These results were found despite Star Excur- sion Balance Test performance during anterior, posteromedial and posterolateral excursions lead to similar specific reach distances in both limbs in either the chronic ankle instability or stable ankle groups. Interpretation: These parameters could be of great interest in detecting dynamic balance impairment in individuals at risk of sprains that might otherwise go undetected by only reach distance assessment. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction and background Ankle sprains are one of the most common lower extremity injuries and the most common injuries in sport. Up to 73% of indi- viduals who sprain their ankles have residual symptoms, repeated sprains and episodes of ‘‘giving way” (Olmsted et al., 2002; Free- man, 1965; Freeman et al., 1965). The development of prevention programmes or preventive behaviours is strongly related to the identification of those at high risk of sprain and/or the factors that increase the risk of ankle sprain (De Noronha et al., 2006). Postural- control deficits during quiet standing after acute ankle sprain and in subjects with chronic ankle instability (CAI) have been fre- quently reported, however, the sensitivity of the measures has been questioned (Olmsted et al., 2002; Freeman, 1965; Freeman et al., 1965; Tropp et al., 1985). In previous research, static and dy- namic balance deficits were identified during single-leg stance in the affected limb of individuals with CAI. However, other studies have reported no differences (Ross and Guskiewicz, 2004; Isakov, 1997). To evaluate proprioceptive and neuromuscular deficits after lower extremity injury, postural control has typically been as- sessed with variations of the Romberg test (Olmsted et al., 2002). The task of maintaining posture during quiet standing may not place adequate demands on the postural-control system in order to detect deficits stemming from ankle-joint injury. These assess- ment techniques may not be sufficiently sensitive to detect mo- tor-control deficits related to impaired functional activity and sport performance. Instrumented devices such as force plates have often been used to quantify postural control during variations of quiet standing (Adlerton et al., 2003). In addition, due to the space and cost requirements associated with these instrumented devices, they are not affordable or practical for many clinical settings. Thus, a simple, reliable and valid method of lower extremity functional performance is needed. One functional clinical test that may be useful to detect deficits related to CAI is the Star Excursion Balance Test (SEBT) (Olmsted et al., 2002; Hertel et al., 2006; Kinzey and Armstrong, 1998). The SEBT is a test of dynamic stability associated with lower extremity pathology that may provide a more accurate assessment of lower extremity functions than tests involving only quiet stand- ing. This test is used in physiotherapy and its assessment depends on the level of training of the therapists and its past experience. It 0268-0033/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.clinbiomech.2009.11.004 * Corresponding author. Address: Studies, Research and Sport Medicine Center, Government of Navarra, C/Sangüesa 34, 31005 Pamplona, Navarra, Spain. E-mail address: mikel.izquierdo@ceimd.org (M. Izquierdo). Clinical Biomechanics xxx (2009) xxx–xxx Contents lists available at ScienceDirect Clinical Biomechanics journal homepage: www.elsevier.com/locate/clinbiomech ARTICLE IN PRESS Please cite this article in press as: Martínez-Ramírez, A., et al. Wavelet analysis based on time–frequency information discriminate chronic ankle instabil- ity. J. Clin. Biomech. (2009), doi:10.1016/j.clinbiomech.2009.11.004