Background: Poor posture is unfortunately wide spreading not only among adults but also among children. Aim of Study: To detect the effect of rounded back posture on the Motor Unit Potentials (MUPs) count of middle trapezius. Patients and Methods: The right and left trapezius motor unit potentials countof 15 normal children (8.64±0.77 years) were compared with 15 children with rounded back (8.92±0.73 years) using electromyography apparatus (EMG). Results: There was a significant increase in the right trapezius motor unit count of the rounded back group compared with that of the normal group (p=0.02). There was no signif-icant difference in the left trapezius motor unit count between the normal and the rounded back groups (p=0.25). Conclusion: Rounded back posture affects the middle trapezius motor unit potential count.