Influence of Posture, Spinal Level, Gender and Muscle Activation on Biomechanical Properties of Lumbar Erector Spinae in Healthy Young Adults.

Background and

Objectives

This study set out to better understand how posture, spinal level, gender and muscle activation influence the biomechanical properties of the lumbar erector spinae (LES) in healthy young adults. We aimed to measure how these factors influence LES tone, stiffness, and damping using a myotonometry device. Materials and

Methods

Thirty healthy young adults (14 males, 16 females; aged 20-25 years) were evaluated at bilateral L3-L5 levels in prone, unsupported sitting, and standing positions, both under relaxed conditions and during submaximal isometric lumbar extension. The myotonometer measured LES tone (Hz), stiffness (N/m), and damping (logarithmic decrement). For each outcome, a mixed-model repeated-measures ANOVA was conducted with Gender as a between-subject factor and Posture, Level, and Action (relaxed vs. contracted) as within-subject factors (Bonferroni-adjusted α = 0.0167).

Results

Posture produced the most significant and consistent effects on all properties-stiffness, tone, and damping (p p p p p

Conclusions

LES biomechanical properties are strongly affected by posture and further modulated by muscle activation, gender, and spinal level. These results support the creation of posture- and gender-specific reference values and underscore the value of dynamic, posture-specific myotonometer-based assessments for paraspinal muscle evaluation and clinical planning.