Objective
To examine back muscle activity and fatigue behavior in female patients with degenerative thoracolumbar kyphosis (DTK) using high-density surface electromyography (HDSEMG) and evaluate the effects of using a soft spinal orthosis.
Methods
Seven female participants with DTK (mean age: 73.6 years) were assessed during static standing and a weighted holding task with and without a soft spinal orthosis. HDSEMG signals were obtained from the lumbar erector spinae using a 64-electrode array. Time to fatigue (TTF), spatial displacement, and directional consistency of muscle activation were analyzed using the spatial center of activity (SCoA) and circular variance (CV).
Results
Orthosis use significantly reduced the sagittal vertical axis and low back pain. TTF was significantly prolonged during the weighted holding task with the orthosis (p=0.012), indicating delayed fatigue onset. SCoA displacement was significantly reduced in both tasks (p<0.001), whereas CV analysis demonstrated improved directional consistency of muscle activation.
Conclusion
HD-SEMG revealed early fatigue onset and unstable muscle activation patterns in patients with DTK, particularly during load-bearing tasks performed without orthotic support. Orthosis used improved endurance and neuromuscular efficiency by reducing spatial and directional variability in muscle recruitment. These findings underscore the utility of HDSEMG for elucidating the neuromuscular pathophysiology of DTK and support the use of spinal orthoses as a conservative treatment approach.