Background

Adolescent idiopathic scoliosis (AIS) is characterized by three-dimensional spinal deformities and muscular imbalances. Muscle activity balance, quantified using RMS (root mean square) values, is essential for assessing recruitment symmetry. sEMG biofeedback has emerged as a key tool to identify asymmetries and guide rehabilitation.

Objectives

1. Investigate muscle activity symmetry between convexity and concavity sides during side-shift overcorrection exercises in AIS patients.

2. Analyze variability patterns across different curve flexibility types.

Methods

Seventeen AIS patients aged 13–20 years (mean height: 167.5 cm; Cobb angle: 27° –55°) were recruited. sEMG biofeedback captured muscle activity over 10 repetitions of 10-second side-shift exercises. Patients were categorized into three flexibility types: Type 1 (flexible), Type 2 (stiff), and Type 3 (rigid). RMS, SD, CV, and output differences were statistically analyzed.

Results

• Convexity muscles showed higher mean RMS values (1.8) than concavity muscles (1.2, p=0.001).

• Balanced RMS (value of 1) occurred in only 18% of exercises, primarily in Type 1 curves.

• Variability: SD—Convexity 0.65, Concavity 0.45; CV—Convexity 36.1%, Concavity 29.7%.

• Maximum output difference: 0.6 RMS.

• Biofeedback impact: “The feedback tones keep me focused during the exercises.”

• Awareness: “I didn’t realize one side was working harder until the machine showed me.”

Discussion

Convexity muscles consistently overactivated, especially in stiff and rigid curves. Results support Mehta, Stendl, and Muryama’s overcorrection and pelvic hitching strategies. Patient feedback underscores biofeedback’s motivational and educational value in promoting muscle symmetry.

Clinical Significance

This study supports biofeedback as a powerful adjunct in AIS rehabilitation. sEMG can personalize interventions and improve outcomes, especially in patients with poor curve flexibility.

Level of Evidence

Level 3: Observational Study without Controls