Participants in this group will receive a six-week school-based physical activity intervention. The intervention will include structured game-based physical activities and neck-shoulder exercises, delivered three times per week.

Participants in this group will receive a six-week health education intervention focusing on posture, screen use, physical activity, and prevention of neck and shoulder pain. The education sessions will be delivered twice per week.

Participants in this group will receive both the six-week physical activity intervention and the six-week health education intervention.

Participants in this group will continue their usual school activities and routine physical education classes without receiving the additional physical activity or health education intervention.

Each intervention session lasted for 70 minutes, conducted three times per week over a six-week period. Each session consisted of a 5-minute warm-up, 30 minutes of structured, game-based moderate-intensity PA, 30 minutes of targeted training for NSP, and a 5-minute cool-down. The intervention ensured appropriate PA volume and intensity for children. It was also designed to maintain high participation levels.

Pain intensity will be assessed using an 11-point Numeric Rating Scale, ranging from 0 to 10, where 0 indicates no pain and 10 indicates the worst imaginable pain. Participants with neck and/or shoulder pain will report their highest pain intensity during the recall period.

Neck and shoulder pain will be assessed using items adapted from the Nordic Musculoskeletal Questionnaire. Participants will report whether they have experienced neck and/or shoulder pain during the past month. The prevalence of neck and shoulder pain will be calculated as the proportion of participants reporting neck pain and/or shoulder pain.

PA was assessed using the Chinese version of the Physical Activity Questionnaire for Children (PAQ-CN), originally developed by Kowalski, Crocker, and Donen (2004) and translated and revised by Guo (2016). The PAQ-CN is a self-administered retrospective PA questionnaire designed for children and adolescents aged 7 to 18 years. It assesses general levels of PA over the previous 7 days through 10 items, each reflecting different activity dimensions during a typical week.The final PAQ-CN score ranges from 1 to 5. PA Level Classification: Based on the final PAQ-CN score, participants are classified into three PA levels:1) Low PA level: PAQ-CN ≤ 2.00 2) Middle PA level: 2.00 < PAQ-CN ≤ 3.003) High PA level: PAQ-CN > 3.00