Development of valid and reliable measures of postural stability

Abstract

Background/objective: The development of simple postural stability tests that relate to performance of activities of daily living (ADL) and can be quickly performed in a clinical setting may assist clinicians in determining appropriate wheelchair configurations and postural supports in an efficient manner. The study's purpose was to validate 3 clinical measures of reach-functional reach (FR), reach area (RA), and bilateral reach (BR)-against the performance of ADL tasks.

Methods: Two groups of 20 subjects differing by time since spinal cord injury were tested. Three measures of reach-FR, RA, and BR-were recorded with and without permitting compensatory strategies. Subjects also attempted a series of ADL tasks. Group 2 subjects participated in test-retest reliability of the reach measures and to measure reach while using compensatory strategies. Correlation, ANOVA, and linear regression were used for analysis.

Results: Regression analysis showed that injury level was a significant predictor of success in performing ADL tasks (%ADL). Significant but not strong correlations were found between %ADL and all uncompensated reach measures. Within Group 2 subjects, compensated FR (r = 0.663) and RA (r = 0.647) were more related to the %ADL score than the uncompensated FR (r = 0.348) and RA (r = 0.305) measurements. BR had the strongest relationship with %ADL scores (P = 0.031) and was the only significant uncompensated reach measurement within the regression analyses.

Discussion and conclusion: While working with clients on seated stability and functional movement, clinicians should be encouraged to incorporate BR tasks because it has the strongest relationship to ADL performance. Researchers interested in studying postural control and stability during functional tasks should consider using uncompensated reach measures.

Figure 1. The functional reach (FR) measure. (a) Starting position. (b) Subject reached as far forward as possible without losing balance.

Figure 2. The reach area (RA) task is a unilateral task that measures the total area encompassed while reaching in lateral, forward, and contralateral directions. (a) Subjects reached in a random order as far as possible without losing their balance in 4 directions and the maximum distance reached was recorded. (b) The measurements defined as RA. During reach, subjects placed the contralateral hand on the umbilicus to negate UE compensatory stabilization.

Figure 3. Bilateral reach (BR) task measures the maximum forward distance that the subject can perform during a bilateral task without loss of balance. Subjects depressed switches positioned in front of each arm. The switches were placed at a minimum forward distance of 70% of arm length and progressively moved outward in 10% intervals.