Exploring New Frontiers: A Cross-Sectional Analysis of Explosive Phase and Muscle Activation During Maximal Biting in Women with Temporomandibular Disorder and Orofacial Pain.

Background: Temporomandibular disorders (TMDs) are associated with altered masticatory muscle function and pain. Although electromyographic parameters have been extensively studied, the rate of force development (RFD) remains an underexplored biomarker in this context. Objective: Analyze the RFD differences in women diagnosed with and without TMD. As a secondary outcome, the masseter and temporalis muscle pre-activation values were compared between groups based on the biting force onset. Additionally, neuromuscular efficiency analysis was also performed. Methods: A retrospective analysis of 62 medical records (41 with TMD, 21 controls) was conducted. Electromyographic activity and bite force were measured during three 5-s maximal biting tasks using synchronized surface electromyography (sEMG) and a laboratory-grade load cell. RFD was computed from force-time curves. Muscle pre-activation was assessed based on sEMG activity immediately preceding contraction onset. Results: The TMD group showed a significantly smaller RFD (mean = 85.5 N/s) compared to controls (mean = 109.0 N/s; p = 0.03; Cohen's d = 0.5). No significant differences were found in neuromuscular efficiency and pre-activation or post-activation levels of the masseter and temporalis muscles between groups. Conclusions: RFD distinguishes women with TMD from healthy controls and may represent a sensitive biomechanical marker of neuromuscular adaptation in TMD, although confirmatory studies are needed. The absence of neuromuscular efficiency and pre-activation differences suggests compensatory neuromuscular mechanisms. Further prospective studies are needed to validate these findings and explore clinical applications.