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

• Grant number: 24/16019-7
• Support Opportunities: Scholarships in Brazil - Master
• Start date: December 01, 2024
• End date: November 30, 2026
• Field of knowledge: Health Sciences - Physiotherapy and Occupational Therapy
• Principal Investigator: Isabel de Camargo Neves Sacco
• Grantee: Milena Bürgel Murari Fernandes
• Host Institution: Faculdade de Medicina (FM). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Context: Sports activities provide various health benefits but can also present risks of musculoskeletal injuries. Acute ankle sprains are among the most common injuries, particularly in young athletes, and can lead to a set of post-injury symptoms known as chronic ankle instability. This condition results from sensory-motor and mechanical failures, affecting quality of life and increasing the risk of ankle osteoarthritis. Studies still diverge on the strength deficits and neuromuscular control in these individuals. High-density electromyography (EMG-HD) offers the extraction of information on motor unit conduction properties, motor unit firing rates, and fiber recruitment strategies, potentially advancing the understanding of muscle control in chronic ankle instability, differentiating individuals who return to activity without symptoms (copers) from those who develop chronic instability (non-copers).Objective: This study aims to better understand the motor complexity and neuromuscular control of the ankle in individuals with chronic instability (non-copers) and without chronic instability (copers) through EMG-HD. The hypothesis is that non-copers will exhibit lower muscle complexity, slower muscle conduction velocity, and reduced force variability compared to copers and controls.Methods: A total of 48 physically active individuals will be recruited. Participants will be screened and assessed with validated questionnaires and submitted to EMG-HD and force analysis during isometric contractions. Data will be analyzed to quantify force variability, muscle activity complexity, and muscle fiber conduction velocity. For force analysis, signals will be processed off-line using MATLAB. For low-level force recordings, variability will be quantified by standard deviation, while variability structure will be assessed by sample entropy. For EMG-HD analysis, root mean square (RMS) values will be calculated for each force level and normalized to a reference value. Sample entropy will be used to characterize muscle activity complexity, and muscle fiber conduction velocity (MFCV) will be estimated in the frequency domain. Statistical analysis will be performed using bidirectional mixed ANOVAs comparing the three experimental groups, followed by Newman-Keuls post hoc tests, with a significance level set at 0.05.