Ultrasound-based assessment of voluntary activation of selected stabilizing muscles in healthy young adults

Introduction. Conscious activation of deep core muscles is a key element of motor control training and rehabilitation for spinal dysfunctions. Learning to effectively engage these muscles can help improve posture and reduce injury risk. Aim of the study. This study aimed to evaluate the activation potential of selected stabilizing muscles – longus colli, serratus anterior, transversus abdominis, and lumbar multifidus – by comparing their thickness at rest and during contraction using ultrasound imaging. Material and methods. A total of 109 healthy young adults (42 men and 67 women, aged 19–25) participated in the study. Muscle thickness was measured at rest and during isometric contraction using ultrasound. Paired t-tests and effect sizes (Cohen’s d) were calculated. Results. A statistically significant increase in thickness was observed only in the transversus abdominis (p = 0.0012; d = 1.48), suggesting effective voluntary activation. The remaining muscles showed no significant changes, with small effect sizes. Conclusions. Among the tested muscles, only the transversus abdominis showed a clear response to voluntary activation cues, highlighting its importance in core training. Other muscles may require more targeted approaches such as neuromuscular training or biofeedback. Ultrasound proved to be a reliable tool for assessing deep muscle engagement.