Strain-based biomarkers at the skin surface detect changes in soft tissue mobility linked to myofascial pain following soft tissue manipulation intervention

BackgroundSoft tissue manipulation is a widely used massage-based intervention for treating myofascial pain, yet its efficacy in increasing tissue mobility is primarily assessed through subjective clinical observations. While patient-reported outcomes often indicate symptom relief, the mechanical changes underlying these improvements remain unclear. No objective gold standard exists for assessing soft tissue mobility; current methods either measure stiffness in small tissue regions, which do not directly capture the lateral mobility between fascial layers, or rely on subjective assessments during clinical palpation. Optical measurement of tissue mobility from the skin surface, captured during hands-on assessment, offers an objective approach that is complementary with routine clinical practice. MethodsThis study used digital image correlation to capture skin surface deformation during hands-on assessment of the cervicothoracic region. Nineteen participants underwent a standardized soft tissue manipulation (STM) intervention protocol. Tissue mobility was measured immediately before and after intervention, considering tissue pull direction (superior vs. inferior relative to the participants back) and bilateral anatomy (left vs. right body sides). From these measurements, eleven strain-based biomarkers were derived to evaluate tissue glide and deformation. ResultsAcross the population, several biomarkers changed significantly following intervention. At the individual level, STM intervention produced tissue mobility changes in nearly all treated participants, with 88% (15 of 17) improving in mobility on at least one body side. Among participants with baseline bilateral pain asymmetries, 90% showed greater mobility gains on their more painful side, reflecting alignment between tissue responsiveness and symptom severity. Baseline bilateral mobility asymmetries were observed in 53% of participants (10 of 19), eight of whom also reported pain asymmetries; in all cases, the less mobile side corresponded to the more painful side. ConclusionsThis study demonstrates that optically derived measures of tissue glide and deformation can objectively detect changes in soft tissue mobility immediately following an STM intervention. Mobility gains closely align with self-reported pain, supporting the clinical relevance of strain-based biomarkers. These findings underscore the potential of this quantitative approach to complement clinical assessments of myofascial restriction and therapeutic response.