The intra-rater reliability and agreement of compensatory stepping thresholds of healthy subjects

The purpose of this study was to evaluate the test-retest, intra-rater reliability and agreement of compensatory stepping thresholds. A protocol was developed to establish anteroposterior single-stepping thresholds, anteroposterior multiple-stepping thresholds, and lateral single-stepping thresholds. Healthy, young subjects stood on a microprocessor-controlled treadmill, and responded to three series of progressively challenging surface translations. Subjects were instructed to "try not to step'' when establishing single-stepping thresholds or "try to take only one step'' when establishing multiple-stepping thresholds. Stepping thresholds were defined as the minimum disturbance magnitude that consistently elicited a single or second compensatory step. Thresholds were expressed as the ankle torque necessary to maintain upright posture. Thresholds studied included anterior single-stepping thresholds (tau = 273.0 +/- 82.3 N m), posterior single-stepping, thresholds (tau = 235.5 +/- 98.0 N m), anterior multiple-stepping thresholds (tau = 977.0 +/- 416.3 N m), posterior multiple-stepping thresholds (tau = 701.9 +/- 237.5 N m), stability-side lateral single-stepping thresholds (tau = 225.7 +/- 77.7 N m), and mobility-side lateral single-stepping thresholds (tau = 236.8 +/- 85.4 N m). Based on intraclass correlation coefficients (ICC) and Bland-Altman plots, all thresholds demonstrated excellent reliability (ICC(2,1) = 0.87-0.97) and agreement. These results suggest that compensatory stepping thresholds have sufficient repeatability to be used in clinical and research-related assessments of fall-risk. Additional study is needed to determine the intra-and inter-rater reliabilities and validity of thresholds specific to the patient populations of interest. (C) 2013 Elsevier B.V. All rights reserved.