Background: Heavy school bags commonly contribute to neck and upper-back pain in school-going children by causing strain and inflammation of the trapezius muscle. Action Observation Therapy (AOT), which involves observing and imitating movements, has shown benefits in improving motor control and reducing pain. This study aims to evaluate the effectiveness of AOT in managing trapezitis caused by heavy school bags in school-aged students.

Methods: A total of 53 school-going students aged 10–16 years with trapezitis due to heavy school bags were randomly allocated into two groups. Group A (experimental) received Action Observation Therapy along with conventional physiotherapy, while Group B (control) received conventional physiotherapy alone. The intervention was administered for 2 weeks, with two 30-minute sessions per week.

Results: A total of 53 participants were included, with 26 in Group A and 27 in Group B. Within-group analysis showed that both groups had statistically significant improvements in pain intensity (NPRS) and neck-related disability (NDI) from pre-test to post-test (p < 0.001). Group A demonstrated a marked reduction in NPRS (5.6 ± 0.7 to 3.8 ± 0.7) and NDI scores (19.9 ± 3.4 to 13.3 ± 2.7). Group B also showed significant improvements, with NPRS reducing from 5.9 ± 0.9 to 4.7 ± 0.9 and NDI from 19.8 ± 3.5 to 16.1 ± 1.9. Between-group comparison revealed significantly greater improvements in Group A compared to Group B. The percentage reduction in both NPRS and NDI was higher in Group A, indicating superior effectiveness in reducing pain and improving functional disability.