Investigation of the motor complexity and neuromuscular control through high density surface EMG in people with ankle chronic instability

• Grant number: 25/10622-6
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: September 01, 2025
• End date: August 31, 2026
• Field of knowledge: Health Sciences - Physiotherapy and Occupational Therapy
• Principal Investigator: Isabel de Camargo Neves Sacco
• Grantee: Lucas da Silva Fernandes
• Host Institution: Faculdade de Medicina (FM). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Context: Chronic ankle instability (CAI) is a prevalent musculoskeletal condition, often resulting from recurrent lateral ankle sprains. It is characterized by repeated episodes of giving way, persistent pain, and functional limitations, even in the absence of clear structural injuries. Studies have shown that individuals with CAI exhibit deficits in motor control and neuromuscular activation, which can be more accurately assessed using high-density surface electromyography (HD-EMG), a technique capable of capturing the spatial and temporal organization of muscle activity. In parallel, functional tests such as the Y-Balance Test (YBT) and the Side Hop Test have demonstrated sensitivity in identifying deficits in dynamic stability and postural control in individuals with CAI and are widely used in both clinical and research settings. Objective: To investigate the variability magnitude (standard deviation and coefficient of variation) and variability structure (sample entropy) of force and electromyographic (HD-EMG) signals of ankle muscles (tibialis anterior, medial gastrocnemius, and peroneus longus) during low-intensity isometric contractions (10%, 30%, 50%, and 70% of maximal voluntary contraction) in different directions (plantarflexion, dorsiflexion, inversion, and eversion), and to correlate these findings with functional performance in clinical tests (Y-Balance Test and Side Hop Test) in individuals with CAI and healthy controls. Methods: This is a cross-sectional analytical observational study involving physically active individuals, divided into two groups: CAI and control, totaling 34 participants. Sample size was calculated based on an effect size of 0.42, statistical power of 0.8, alpha level of 0.05, and using ANOVA for repeated measures (4 levels) and 2 groups. All the 34 participants will perform isometric ankle contractions in different directions and intensities using a custom-built dynamometer, with simultaneous acquisition of force and HD-EMG signals. The following variables will be extracted from the EMG signals: amplitude (RMS), structure (sample entropy) and magnitude of the variability (standard deviation and coefficient of variation). The YBT and Side Hop Test will be conducted following standardized protocols, with a collection of metrics such as absolute and normalized reach distances (YBT) and total time to complete ten hops (Side Hop Test). Data will be statistically analyzed to compare groups and examine correlations between neuromuscular and functional variables. (AU)