Visual monitoring in real-time improves consistency of 3D IASTM force applied to humans

Abstract Background Instrument-assisted soft tissue manipulation (IASTM) is widely used, yet clinicians mostly rely on their subjective perception of applied force which can lead to variability. No studies have determined intra- and inter-examiner reliability of three-dimensional (3D) IASTM force–motions applied to humans. The objective of this study was to evaluate whether real-time visual monitoring enhances consistency of applied IASTM force. Methods This study was an observational reliability study with blinded assessors. 45 healthy adults were enrolled between June to December 2021. Clinicians (two novice, two experienced) applied 1-inch IASTM linear strokes using two quantifiable soft tissue manipulation (QSTM) smart devices (localized; dispersive) to lumbar and calf regions under two conditions: (1) applying self-perceived “medium” force without visual monitoring, and (2) applying force guided by real-time visual monitoring from a graphic visual interface (GVI). Triaxial (3D) average peak force (primary variable), stroke frequency, and angle were measured. Linear mixed models and variance components evaluated repeatability and reproducibility within and between clinicians and across two sessions. Results Visual monitoring substantially reduced variability in average peak force across clinicians, regions, devices, and sessions. Standard deviations (SDs) were significantly larger and ranges meaningfully broader without monitoring compared to with monitoring. Monitoring improved intra- and inter-examiner consistency by ≥ 30% in nearly all conditions, with medium to very large effect sizes. Effects on stroke frequency were mixed, and influence on angle minimal. Conclusions Visual monitoring in real-time significantly improved the consistency of 3D IASTM force applications on humans. Optimal reliability is foundational to practice fidelity, training, and more rigorous investigation of dose–force response relationships in manual therapy. Trial Registration : The study was prospectively registered at ClinicalTrials.gov (Identifier: NCT04923633).