Background and Purpose Quantitative assessment of reactive balance often requires large, costly equipment, limiting its use in clinical practice. This study investigated the inter-rater reliability of the instrumented lean-and-release (iLEAN) test, a manual reactive balance assessment designed to provide a practical alternative for physiotherapists.

Methods Sixteen healthy young women wore knee braces, weighted vests, and ankle weights to simulate reduced physical function typical of older adults. Participants completed the iLEAN test in standing, where reactive balance control was assessed in forward, left, right, and backward directions. During tests, an assessor applied the iLEAN device against the shoulder and released support once the participant reached a target lean load, which was progressively increased until balance could not be regained with a single step. Inter-rater reliability was analyzed using intraclass correlation coefficients (ICC, model 2,1) and Bland–Altman plots.

Results The ICCs (95% confidence intervals) for the iLEAN scores were 0.60 (0.17– 0.84) for forward, 0.75 (0.34–0.92) for left, 0.80 (0.45–0.94) for right, and 0.83 (0.58– 0.94) for backward. Bland–Altman analysis revealed no systematic bias between raters across all directions.

Discussion The iLEAN demonstrated acceptable inter-rater reliability in all directions, with the backward test showing the highest consistency. These findings suggest the iLEAN, particularly in the backward direction, may provide physiotherapists with a reliable and practical method to monitor changes in reactive balance control during exercise or rehabilitation, without reliance on specialized laboratory equipment.

The authors have declared no competing interest.

This study did not receive any funding.

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

The study was approved by the Office of Research Ethics at Kanagawa University of Human Services (Approval No. 18-23-34).

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All data produced in the present study are available upon reasonable request to the authors.