Background & Objective: Traditional models of “abdominal support” may underestimate the role of the pelvic floor–diaphragm–laryngeal synergy in managing breath for both speaking and singing. The rectus abdominis, primarily a trunk flexor, contributes minimally to expiratory pressure control during phonation. This study investigated how pelvic floor muscle (PFM) activation, in coordination with orofacial and abdominal systems, influences subglottal pressure (Psub), laryngeal efficiency, and acoustic stability in females with Functional Musculoskeletal Dysregulation (FMD)—defined as the presence of Muscle Tension Dysphonia (MTD), Temporomandibular Disorder (TMD), or Pelvic Floor Dysfunction (PFD).

Methods/Design: Forty-eight females were assigned to a 2×2 factorial design (n=12/group): (1) Non-singers without FMD, (2) Non-singers with FMD, (3) Singers without FMD, and (4) Singers with FMD. MTD, TMD, and PFD were coded as three independent binary factors (present/absent) to preserve comorbidity. Participants completed speech and singing tasks (conversational speech, reading, pitch glides, sustained vowels, and vibrato) under combined surface electromyography (sEMG), 3D motion capture (MOCAP), and acoustic recording. PFM sEMG (Delsys Trigno Mini, 1000 Hz) followed the Glazer protocol to record levator ani activity. Abdominal (rectus, oblique, transversus) and orofacial (masseter, submental) EMGs were synchronized with acoustic and kinematic data. Psub was measured noninvasively via intraoral pressure during bilabial /p/ occlusions using a 3 mm oral tube connected to a ±2 kPa transducer.

Results: Higher PFM activity correlated with stable Psub (r = 0.61, p < 0.01) and reduced laryngeal constriction. FMD participants showed asynchronous or uncoordinated PFM–laryngeal co-activation (p < 0.05), often with jaw rigidity and tongue-root elevation. PFM–jaw synchrony predicted vibrato and prosodic stability (p < 0.01). Participants with PFD or atypical hormonal fluctuations showed lower pelvic tone, greater Psub variability, and mismatched perceptual self-ratings, suggesting disrupted body-schema integration.

Conclusions: This factorial design demonstrated that both vocal training (speaking vs. singing) and Functional Musculoskeletal Dysregulation may independently and interactively shape respiratory–phonatory efficiency. Coordinated activation of the levator ani–diaphragm–laryngeal axis supports stable pressure and efficient voicing, whereas coexisting MTD, TMD, or PFD compromise acoustic regularity and psychosomatic interoception of vocal motor processes. These findings advance a whole-body, endocrine-sensitive model of vocal production by providing novel empirical evidence that pelvic floor activity contributes to subglottal pressure stability and vibrato control, highlighting a novel cross-system mechanism of respiratory–phonatory coordination and supporting the integration of pelvic and orofacial awareness into voice training and therapy to enhance breath management and long-term vocal efficiency.