Clinical assessment of reactive balance control in acquired brain injury: A comparison of manual and cable release‐from‐lean assessment methods

Abstract

Objective Perturbation‐evoked stepping reactions are infrequently assessed directly in clinical settings even though stepping reactions in response to a sudden loss‐of‐balance perturbation ultimately determine whether a fall occurs. Individuals with acquired brain injury (ABI) due to stroke who are ambulatory and awaiting hospital discharge have been found to exhibit delayed stepping reactions but are typically discharged without assessment of perturbation‐evoked stepping. Tests that specifically target the capacity to perform perturbation‐evoked stepping reactions are important to identify those at risk for falls and to direct intervention strategies. The aim of this study was to evaluate agreement and reliability of two assessment methods used to assess rapid stepping reactions, specifically in individuals with ABI due to stroke or other causes. A secondary aim was to compare perturbation‐triggered biomechanics of the two assessment methods. Methods Thirty‐five participants who were less than 4 months post‐ABI were evaluated in an inpatient unit at the Toronto Rehabilitation Institute. Stepping reactions were assessed using manual release‐from‐lean and cable release‐from‐lean perturbation‐based assessment methods. Results There was moderate agreement between the assessment scores resulting from the two assessment methods (κ = 0.55) and substantial test–retest reliability (κ's > 0.61) for both assessment methods. There was no evidence that the assessment score was affected by assessment method, test–retest, or assessment order. However, the cable release from lean resulted in a more rapid release of the lean support force (2 ms vs. 125 ms) and earlier foot‐off times (340 ms vs. 401 ms) compared with the manual release from lean. Conclusion Delays in foot‐off time associated with the manual release‐from‐lean perturbation raise concerns that the manual assessment method may not provide a perturbation that is sufficiently challenging to reveal a patient's balance‐recovery capacity and associated fall risk. However, the manual assessment requires no equipment and the assessment score may provide a useful indication of gross reactive balance control.

Perceived timing of postural instability onset

“…Participants were first weighed to determine the 7-8% lean angle to be utilized during the study. Participants were then fitted with a full-body harness that allowed for the attachment of a lean cable at the level of the 2nd and 3rd thoracic vertebrae and a safety rope, which was secured to the ceiling [9,10,27,28]. Participants were positioned ∼1m from the lean-and-release apparatus, and their feet were positioned in a standardized position [9,10,29].…”

“…Postural perturbations were evoked by a lean-and-release mechanism and an auditory reference stimulus was produced through headphones. The postural perturbations produced a large enough perturbation to inherently evoke a stepping response in each of the participants [9,10,27,30,31]. Participants then made non-speeded TOJ responses with the use of handheld buttons (left button - auditory reference first; right button - postural perturbation first).…”

Catching and throwing exercises to improve reactive balance: A randomized controlled trial protocol for the comparison of aquatic and dry-land exercise environments

“…During the testing, the quality of the compensatory reactions will be scored using the Reactive Postural Control section of the mini‐BESTest [ 39 , 40 ]. The scores will be ranged from 0 to 2.…”

“…Force data in relation to the cable release will be extracted for further analysis to define the reaction time. Foot-off and foot contact will be defined as the time (ms) following the cable release at which the force under the stepping foot becomes less than and greater than 1% of the body weight, respectively [ 40 ]. Hand contact with the handle during REACH will be defined as the time following the cable release at which the force sensitive resistor detects a force.…”

Responses to external repeated perturbations vary with time intervals

“…Those training programs are considered to improve anticipatory and compensatory postural adjustments [6] , [7]. Various modalities have been utilized to apply a postural perturbation using mechanisms, including a translating platform [8], pulling a cable attached to an individual's waist [8], sternal nudge [9], and release-from-lean [10]. The relationship between perturbation training and fall risk appears correlated, despite barriers to clinical adoption.…”