Contents lists available at ScienceDirect Human Movement Science journal homepage: www.elsevier.com/locate/humov Full Length Article Electromiography comparison of distal and proximal lower limb muscle activity patterns during external perturbation in subjects with and without functional ankle instability Khadijeh Kazemi a , Amir Massoud Arab a , Iraj Abdollahi a , Daniel López-López b, ⁎ , César Calvo-Lobo c a Department of Physiotherapy, University of Social Welfare and Rehabilitation Sciences, Evin, Koodakyar Ave., Tehran, Iran b Research, Health and Podiatry Unit, Department of Health Sciences, Faculty of Nursing and Podiatry, Universidade da Coruña, Spain c Nursing and Physical Therapy Department, Institute of Biomedicine (IBIOMED), Faculty of Health Sciences, Universidad de León, Ponferrada, León, Spain ARTICLE INFO Keywords: Ankle injuries Electromyography Joint instability Ligaments Muscle contractions ABSTRACT Ankle sprain is one of the most common injuries among athletes and the general population. Most ankle injuries commonly affect the lateral ligament complex. Changes in postural sway and hip abductor muscle strength may be generated after inversion ankle sprain. Therefore, the con- sequences of ankle injury may affect proximal structures of the lower limb. The aim is to describe and compare the activity patterns of distal and proximal lower limb muscles following external perturbation in individuals with and without functional ankle instability. The sample consisted of 16 women with functional ankle instability and 18 healthy women were recruited to participate in this research. The external perturbation via body jacket using surface electromyography, amplitude and onset of muscle activity of gluteus maximums, gluteus medius, tibialis anterior, and peroneus longus was recorded and analyzed during external perturbation. There were dif- ferences between the onset of muscles activity due to perturbation direction in the two groups (healthy and functional ankle instability). In the healthy group, there were statistically sig- nificant differences in amplitude of proximal muscle activity with distal muscle activity during front perturbation with eyes open and closed. In the functional ankle instability group; there were statistically significant differences in amplitude of proximal muscle activity with distal muscle activity during perturbation of the front and back with eyes open. There were statistically significant differences in the onset of muscle activity and amplitude of muscle activity, with-in and between groups (P < 0.05). Therefore, in the presence of functional ankle instability, ac- tivation patterns of the lower limb proximal muscles may be altered. 1. Introduction Ankle sprain is one of the most common injuries among athletes and general the population (Gribble & Robinson, 2009). Excessive plantar flexion and inversion are the most common causes of injury of lateral ligament complex (Brown & Mynark, 2007; Clark & Burden, 2005). About 80% of the people will experience ankle sprain during their life span (Akhbari, Ebrahimi Takamjani, http://dx.doi.org/10.1016/j.humov.2017.08.013 Received 15 May 2017; Received in revised form 16 August 2017; Accepted 16 August 2017 ⁎ Corresponding author at: Universidade da Coruña, Unidade de Investigación Saúde e Podoloxía, Facultade de Enfermaría e Podoloxía, Departamento de Ciencias da Saúde, Campus Universitario de Esteiro s/n, 15403 Ferrol, Spain. E-mail addresses: kh.kazemi63@gmail.com (K. Kazemi), arabloo_masoud@hotmail.com (A.M. Arab), Irajabdollahi@hotmail.com (I. Abdollahi), daniellopez@udc.es (D. López-López), cecalvo19@hotmail.com (C. Calvo-Lobo). Human Movement Science 55 (2017) 211–220 0167-9457/ © 2017 Elsevier B.V. All rights reserved. MARK