Multimodal Biomechanical, Neuromuscular, and Sensorimotor Alterations Associated with Prolonged Smartphone Use and Their Response to Targeted Physiotherapy Intervention

Abstract Smartphone use has emerged as a significant risk factor for cervical musculoskeletal dysfunction, yet the integrated mechanistic pathways remain inadequately characterized. This study examined the temporal relationship between smartphone exposure and biomechanical, neuromuscular, and sensorimotor alterations in the cervical spine, coupled with physiotherapy-driven recovery mechanisms. We conducted a prospective, randomized controlled trial with 94 asymptomatic to minimally symptomatic smartphone users (age 18-35 years, daily usage≥4 hours). Three-dimensional cervical spine kinematics during real-world smartphone use were captured via Inertial Measurement Units (IMU), alongside surface Electromyography (sEMG) of the deep cervical flexors, upper trapezius, and scapular stabilizers. Cervical proprioception was quantified through joint position sense testing and head repositioning accuracy; balance was assessed via dynamic posturography. Cranio-Vertebral Angle (CVA), Neck Disability Index (NDI), and Pressure Pain Threshold (PPT) were measured at baseline, 8 weeks, and 16 weeks. The intervention group (n=47) received targeted motor control retraining emphasizing deep cervical flexor activation, neuromuscular re-education via electromyographic biofeedback, and ergonomic correction protocols. Controls (n=47) received standard postural education. Repeated-measures ANOVA and independent t-tests examined within- and between-group differences (α=0.05). Smartphone use induced anterior cervical translation averaging 4.2±1.8 cm, accompanied by 73-87% elevation in normalized cervical erector spinae activity and 52% reduced upper trapezius activation efficiency. Proprioceptive deficits manifested as Joint Position Error (JPE) of 8.3±2.1° and impaired cervical rotation range. Post-intervention, the motor control group demonstrated significant CVA improvement (5.7±2.1°, p<0.001), JPE reduction to 2.8±1.4° (p<0.001), and 67% improvement in upper trapezius coordination (p<0.01). T he integrated neuromuscular-proprioceptive restoration proved superior to postural education alone, establishing direct links between mechanistic pathways and functional recovery. These f indings support comprehensive assessment and targeted physiotherapy intervention addressing the triadic dysfunction inherent to technology-driven postural disorders.