In Vivo Evidence of Myofascial Force Transmission Along the Posterior Spiral Chain: Functional Connectivity Linking the Contralateral Latissimus Dorsi, Thoracolumbar Fascia, and Gluteal Region

Myofascial force transmission has been proposed as a mechanism by which mechanical stimuli applied to one body region can influence the behavior of distant segments through fascial continuity. The posterior spiral chain (PSC), linking the latissimus dorsi, thoracolumbar fascia, and contralateral gluteal region, has been described anatomically, but its functional relevance in vivo remains incompletely understood. A single-group pre-post experimental study was conducted on 73 healthy participants. Trunk rotation in the transverse plane was assessed using inertial digital goniometry under four conditions: two baseline assessments, isometric activation of the PSC via right hip abduction-external rotation, and post-stretching of the caudal segment of the PSC (right or left side, alternating allocation procedure). Left and right trunk rotation, total rotational range of motion (ROM), and rotational balance were analyzed. Baseline trunk rotation showed no lateral asymmetry and no sex-related differences. Isometric activation of the PSC induced a marked redistribution of trunk rotation, characterized by a significant increase in left rotation and a concomitant reduction in right rotation, with only a small reduction in total ROM. Stretching produced a partial rebalancing of the activation-induced asymmetry. While total ROM did not differ between stretching sides, rotational balance shifted toward the treated side, indicating a direction-specific effect. Modulation of myofascial tension along the posterior spiral chain alters trunk rotational patterns in vivo without increasing overall rotational amplitude. These findings support the functional relevance of the PSC and suggest that myofascial interventions may primarily act by redistributing available motion rather than by increasing total range of motion, with potential implications for the assessment and treatment of rotational dysfunctions.