Proprioception Training and Surrogate Outcomes: A Systematic Review of Definitions, Measures, and Effectiveness Claims.
BACKGROUND: "Proprioception training" is widely advocated in rehabilitation and sports practice, yet the term encompasses heterogeneous constructs, interventions, and outcomes. Many trials infer proprioceptive benefits from surrogate outcomes (balance, strength, or pain) rather than direct psychophysical indices. OBJECTIVE: We aimed to examine how proprioception is defined and measured, and how improvement is claimed, in randomized controlled trials. METHODS: Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020, PubMed, Scopus, and Web of Science were searched to October 2025. Eligible randomized controlled trials explicitly described interventions as "proprioceptive" or "sensorimotor training" and reported at least one proprioceptive outcome, either direct (e.g., joint position reproduction, threshold to detection of passive motion, active movement extent discrimination) or indirect (e.g., sway, balance). Methodological quality was appraised with the Physiotherapy Evidence Database (PEDro) scale and risk of bias using the Cochrane Risk of Bias 2 (RoB 2) tool. RESULTS: Fifty-one randomized controlled trials (n = 2319) were included. Comparative synthesis showed that improvements inferred from surrogate outcomes were more frequent and often larger than improvements observed in direct psychophysical measures. Directly targeted practice, angle specific, attentionally demanding, and aligned with the measured proprioceptive submodality and task construct, produced the most consistent benefits in position-reproduction accuracy/error, movement-detection sensitivity, or discrimination performance, depending on the outcome assessed. In contrast, multimodal regimens (balance, strengthening, taping, manual therapy) commonly improved balance, pain, strength, or function without comparably consistent evidence of enhanced direct psychophysical proprioceptive function. CONCLUSIONS: Specific psychophysical components of proprioceptive function appear modifiable, but only when training explicitly targets the sensory construct measured. The field remains conceptually diffuse, with frequent conflation of sensorimotor performance and proprioception. Progress depends on defining proprioceptive submodalities a priori, privileging validated psychophysical outcomes over surrogate outcomes, and aligning intervention content with measurement to substantiate true perceptual learning rather than generic motor adaptation.