The study of individual perception and neural control underlying movement in coordinating postural control when there is an increase in complexity of environmental and task constraints in CAI individuals compared to healthy controls

UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
Yuki A. Sugimoto (Creator)
The University of North Carolina at Greensboro (UNCG )
Web Site:
Scott Ross

Abstract: Individuals with Chronic Ankle Instability (CAI) commonly exhibit postural control (stability, adaptation) deficits and altered gait (walking, running) mechanics (Hertel, 2008; Hertel and Corbett, 2019). These impairments in motor behaviors have been hypothesized to be a result of inadequate, yet inherent interactions between individual perception (i.e., sensory systems) and movement (action) integrated at the central nervous system (CNS), resulting in less flexible and adaptable sensorimotor systems. Flexibility and adaptability of sensorimotor systems reflecting on underlying biological noise (movement variability) are critical to coordinate the sensory reweighting system. The sensory reweighting system assigns a relative weight to each sensory system based on the complexity of organismic, environmental, and task constraints to convey redundant and convergent sensory feedback at the CNS. An adequate sensory reweighting system results in sufficient multisensory integration by filtering all potential distractors, the irrelevant sensory information, to the context (e.g., task goals). Successful multisensory integration allows the CNS to integrate the context-relevant sensory information necessary to manage postural control that is the foundation of motor control to achieve suitable performance and adapt to a sudden environmental change. However, the gap exists in the literature to understand the integration phenomenon on how individual elements (i.e., sensory reweighting system, movement variability) contribute to the interaction between perception and movement, especially when environmental and task constraints increase in the same cohort of participants with and without CAI. Therefore, the primary purpose of this study was to understand the modulation of 1) the sensory reweighting system and postural control, 2) postural adaptation to a sudden change in the environment in the direction of lateral ankle sprain mechanisms, and 3) movement variability, an underlying biological noise pertaining to postural control, when the complexity of environmental and task constraints are manipulated in CAI individuals compared to healthy controls. A total of 44 physically active individuals, consisting of 22 individuals with CAI (13 females, 9 males; age: 26.09 ± 5.76 years; height: 172.25 ± 9.76 cm; weight: 76.18 ± 14.91 kg) and 22 individuals without CAI (13 females, 9 males; age: 25.41 ± 5.92 years; height: 169.70 ± 9.32 cm; weight: 71.98 ± 14.79 kg) volunteered to participate in this mixed-model repeated-measures study. The NeuroCom Sensory Organization Test (SOT) and Adaptation Test (SMART EquiTest, NeuroCom International Inc., Clackamas, OR) were utilized to examine postural control (equilibrium scores), postural adaptation (sway energy scores), the sensory reweighting system (sensory reweighting ratios), and movement variability (sample entropy) while controlling posture in double- and single-limb (injured, uninjured) stances in individuals with and without CAI. Interestingly, CAI individuals controlled posture very similar to healthy controls. The unique finding of this study was that group differences in the sensory reweighting system depended on both task constraints and sensory systems; CAI individuals upweighted on vestibular feedback when the SOT manipulated somatosensory and visual feedback while controlling posture in the injured-limb. Both groups weighted on somatosensory and visual feedback similarly with continuous emphasis on vision during individual tasks (stance limbs: double, injured, uninjured). Therefore, we contend CAI individuals upweighted on vestibular feedback, which is an independent sole veridical reference to self-motion, when sensory conflicts and task constraints became greater standing in the injured-limb. These findings also imply an effective multisensory integration among CAI. CAI individuals exhibited respective superior postural adaptation to a sudden environmental change in a support surface with plantarflexion rotation and in the uninjured-limb than healthy controls. Superior postural adaptation is indicative of pre-programmed feedforward motor control. In addition, lower movement variability in postural control was noted in the uninjured- and injured-limbs in CAI. Group differences in movement variability depended on task constraints: those individuals with CAI lowered variability in the uninjured-limb when no sensory feedback was manipulated, and in both the uninjured- and injured-limbs when they were forced to reweight on vestibular feedback with manipulation of somatosensory and visual feedback. Lowered movement variability exhibited with an increase in task constraints in the injured- and uninjured-limbs may be indicative of a mechanism that CAI implemented to provide a boundary to freeze the degree-of-freedom (redundancy in sensory feedback) to achieve effective multisensory integration. Collectively, our findings of superior postural adaptation and lower movement variability in postural control for CAI may imply an existent change in central organization and implementation of supraspinal mechanisms of postural control. Furthermore, postural control, postural adaptation, and movement variability in individuals with and without CAI depended on the environmental or task constraints. Environment- and task-dependent postural control, postural adaptation, and movement variability contribute to motor behaviors throughout the lifespan. Therefore, taking a multisensory-feedback approach by recognizing when to increase environmental and task constraints may optimize rehabilitation intervention to prevent subsequent ankle sprains in individuals with CAI.

Additional Information

Language: English
Date: 2021
Ankle, CAI, Perception, Postural Control, Sensory Reweighting, Variability
Ankle $x Disorders
Gait disorders

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