Impact of Short-Term Smartphone Use on Postural Alignment, Muscle Activation, and Mechanical Properties in Adolescent Males: A Randomized Controlled Trial

Purpose: Smartphone use is prevalent among adolescents and is associated with postural and neuromuscular problems.This study examined the effects of short-term seated smartphone use on postural alignment, cervical muscle activation, and the mechanical properties of muscles in adolescent males.Methods: Sixty male adolescents aged 13-18 years were assigned randomly to a smartphone group (n = 30) or an interview group (n= 30).The smartphone group watched videos for 30 minutes, while the interview group completed a verbal interview in the same posture.All participants were assessed at four time points: pre-task, one minute after task initiation, after 30 minutes, and 10 minutes posttask.The sagittal postural alignment was analyzed using reflective markers.Cervical muscle activation was recorded by surface electromyography.The muscle tone and stiffness were assessed using a handheld myotonometer.Repeated-measures ANOVA was used for analysis.Results: The smartphone group showed significant increases in the head and neck flexion angles and thoracic kyphosis over time, with some variables remaining elevated after the task (p< 0.05).Muscle activation increased during and after the task in all measured cervical muscles only in the smartphone group, while no significant changes were observed in the interview group (p< 0.05).The muscle tone and stiffness also increased over time, only in the smartphone group (p< 0.05).Conclusion: Short-term smartphone use in a seated posture induced forward head posture, increased thoracic flexion, and elevated cervical muscle activation and mechanical load in adolescent males.These findings suggest that even brief exposure may adversely affect postural and neuromuscular function in adolescents.