Related Experiment Video
Updated: Aug 6, 2026
Evaluating Postural Control and Lower-extremity Muscle Activation in Individuals with Chronic Ankle Instability
Published on: September 18, 2020
Diagnostic accuracy of biodex balance system stability indices under single- and dual-task conditions in individuals
Nahid Pirayeh1,2, Aida Shahbazi3, Neda Mostafaee4,5
1Rehabilitation Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran. nahid_pt8287@yahoo.com.
Background:
Although balance deficits in chronic ankle instability (CAI) have been well documented, the diagnostic accuracy of instrumented balance measures-particularly under dual-task conditions-for differentiating individuals with CAI from copers remains unclear.
Objective:
To examine the discriminative ability and diagnostic accuracy of Biodex Balance System stability indices, with and without a concurrent cognitive task, in differentiating individuals with CAI from copers.
Methods:
Seventy participants with a history of lateral ankle sprain were classified into a CAI group (n = 35) or a coper group (n = 35) based on clinical history and Identification of Functional Ankle Instability (IdFAI) scores. Dynamic balance was assessed using the Biodex Balance System at stability levels 5 and 7. Anterior-posterior (AP), medial-lateral (ML), and overall stability indices were recorded under single-task and dual-task (cognitive counting) conditions. Receiver operating characteristic (ROC) curve analyses were used to determine sensitivity, specificity, area under the curve (AUC), likelihood ratios, predictive values, and optimal cutoff points.
Results:
Significant between-group differences were observed for 13 of the 24 assessed stability indices, with medium-to-large effect sizes identified for several ML stability measures under dual-task conditions. The ML stability index at level 5 (eyes open with and without a cognitive task), level 5 with eyes closed and cognitive task, overall stability index at level 5 with eyes open and cognitive task, and ML stability index at level 7 with eyes open and cognitive task yielded moderate AUC values (0.71-0.76). Among these measures, the ML stability index at level 7 with eyes open and cognitive task showed the highest sensitivity (0.74) and lowest negative likelihood ratio (0.40), while the ML stability index at level 5 with eyes open demonstrated the highest specificity (0.75) and positive likelihood ratio (2.44).
Conclusion:
Biodex Balance System stability indices, particularly medial-lateral measures obtained under dual-task conditions, demonstrated moderate diagnostic utility for differentiating individuals with CAI from copers. These measures may provide complementary information regarding sensorimotor impairments and may assist clinical assessment and rehabilitation monitoring when used alongside patient history and self-reported instability measures.
