NEURAL MECHANISMS OF SUSTAINED FORCE CONTROL IN ADOLESCENTS WITH JUVENILE FIBROMYALGIA

Juvenile fibromyalgia (JFM) is a chronic pain condition characterized by widespread musculoskeletal pain, often accompanied by fatigue, sensory hypersensitivity, nonrestorative sleep, and affective symptoms. Although neuroimaging studies have shown altered central processing of nociceptive and sensory information in JFM, the neural mechanisms supporting motor effort and force regulation remain poorly understood. Emerging evidence suggests a broader dysfunction extending beyond pain processing to motor performance and sensorimotor integration. We investigated behavioral performance and task-evoked brain activation during force generation and sustained motor control in adolescents with JFM compared with healthy controls (HC). Thirty-eight adolescent girls with JFM and thirty-one HC completed a maximal voluntary contraction (MVC) assessment followed by a sustained handgrip task at 50% of individual MVC. Adolescents with JFM showed reduced MVC capacity and lower mean and maximal force during MVC assessment compared with HC. During the sustained force task, both groups initially reached their target force; however, adolescents with JFM exhibited reduced force output and poorer force maintenance over time, accompanied by increased variability and higher ratings of fatigue and pain. Neuroimaging revealed engagement of the canonical sensorimotor network in both groups, but adolescents with JFM showed reduced task-evoked activity in parietal regions, most prominently in the left superior parietal lobule, with additional hypoactivation in premotor and prefrontal areas during the final task block. Together, these findings indicate altered sensorimotor integration during sustained motor effort in JFM and highlight parietal hypoactivation as a potential neural mechanism linking chronic pain, fatigue, and functional motor impairment.