Objectives: The effects of eccentric exercises on clinical outcomes and central pain mechanisms are unclear in neck/shoulder pain (NSP). The aims were to: (1) evaluate the clinical impact of unilateral eccentric training in female computer users with chronic NSP; (2) compare pressure pain sensitivity, temporal summation of pain (TSP); and conditioned pain modulation (CPM) in female office workers with and without NSP; and (3) assess sensitization and central pain responses after training. Methods: In part A, 20 females with NSP were compared with 20 controls. In part B, the NSP group underwent a 5-week upper trapezius eccentric training program. Participants reported their pain intensity and completed the Neck Disability Index, and the Disabilities of the Arm, Shoulder and Hand questionnaire. Pressure pain thresholds (PPTs) were assessed over the neck and forearm. Cuff algometry identified pain detection threshold (PDT) and pain tolerance thresholds (PTT). TSP was evaluated by visual analog scale pain scores during 10 repetitive cuff stimulations. CPM was calculated as the difference in PDT with and without a conditioning painful stimulus. Outcomes were measured at baseline and after intervention. Pain intensities were collected at 3- and 6-month follow-up. Results: Pain and disability decreased after intervention (P<0.05) and at follow-ups (P=0.002). The NSP group showed reduced PTT (P <= 0.02), but no differences in TSP (P=0.947) or CPM (P=0.059) compared with controls. After training, participants with NSP had improved CPM, PPTs, and PTT at the nontreated side (P<0.05). Discussion: Eccentric training improved pain and disability, reduced sensitization, and enhanced CPM efficiency in female computer users with NSP.