Static Stretching as a Multilevel Mechanobiological Process: An Integrative Narrative Review and Proposed Framework from Mechanical Loading to Biological Adaptation.

Static stretching is one of the most widely prescribed interventions in sports medicine, rehabilitation, and exercise science for improving joint range of motion (ROM) and flexibility. Despite decades of research, however, the biological mechanisms underlying its effects remain incompletely understood. Traditional explanations have primarily focused on muscle extensibility and passive tissue stiffness, whereas emerging evidence suggests that stretching may engage multiple mechanically and biologically interconnected systems. This integrative narrative review aimed to synthesize current evidence on the biological mechanisms underlying static stretching and to propose a conceptual, hypothesis-generating framework linking externally applied mechanical loading with biological responses across multiple levels of organization. Evidence from biomechanics, fascial biology, mechanotransduction, connective tissue biology, vascular physiology, and neuroscience was critically integrated, while distinguishing direct human static-stretching evidence from indirect human, preclinical, and general mechanobiological evidence. Although evidence supports contributions from several of these individual domains, direct human evidence demonstrating their integrated operation during static stretching remains limited. The available evidence therefore suggests that static stretching may be understood more broadly than as a muscle-centered flexibility intervention alone. Mechanical loading during stretching may be transmitted across muscular and connective tissues and interact with mechanosensitive cellular, extracellular-matrix, vascular, inflammatory, and neural processes; however, the directness and strength of evidence for these proposed links vary substantially. The resulting framework provides a plausible, testable hypothesis for how interactions among these processes may contribute to heterogeneous findings and inter-individual variability following stretching interventions, rather than an established explanatory model. Accordingly, this review conceptualizes static stretching as a biologically active mechanical stimulus whose effects may involve interacting responses across multiple levels of biological organization. By integrating evidence from previously separated biological domains while explicitly recognizing differences in evidence directness, the proposed framework provides a theoretical basis for future mechanistic research and for testing the causal and temporal relationships among these candidate processes in humans.