Balancing ‘on edge‘: The effects of fear and anxiety on sensori-motor control of balance

Introduction: Emotions such as fear and anxiety have been strongly linked to balance instability, dizziness and falls. While traditionally, fear and anxiety were only considered to be the negative outcomes of a prior fall, more recent evidence strongly suggests these factors can directly influence clinical and objective measures of balance performance and future fall risk.Methods: In a series of studies involving healthy young and older adults we have manipulated fear and anxiety through changes in environmental or postural threat, such as standing on virtual or real elevated heights, changes in social context, or through the presentation of visual stimuli known to initiate negative emotional responses, in order to quantify the short term (acute) effects on sensori-motor control of static and dynamic balance, underlying spinal and brainstem reflexes, cognitive-attentional processes and balance perceptions (Adkin & Carpenter, 2018).Results: Converging evidence supports direct and indirect effects of fear and anxiety on neuro-mechanical control of balance across a broad range of static and dynamic balance tasks (Adkin & Carpenter, 2018). Fear and anxiety-related changes involve a combination of context-dependent protective strategies, and potentially maladaptive or inefficient neuro-muscular changes that are associated with changes in state-anxiety, attentional focus, and physiological arousal. These maladaptive changes adapt quickly to repeated real and virtual threat exposure and can be modified, to some degree, by distraction tasks such as positive self-talk. Adaptations to repeated exposure appear to persist over time, and can transfer between contexts, providing support for exposure therapy as a potential intervention for anxiety-related balance behaviors. Potential mechanisms underlying threat-related changes and adaptations, include significant increases in sensori-motor gain of proprioceptive and vestibular reflexes, and to a lesser extent for visual and cutaneous reflex pathways. Cortical changes are also likely influenced by anxiety and fear based on observed changes in conscious perception of whole-body movements, sensory-evoked cortical responses, and cortico-muscular coupling.Conclusions: The growing evidence of fear-balance associations in young and older adults provides important insight on the physiological, psychological, and social-cognitive interactions that contribute to human postural control and highlights the need to account for the potential confounding influence of anxiety and fear when performing balance assessments, and designing treatment and intervention solutions for balance deficits and fall prevention.Acknowledgements: This work has been supported by grant funding from the Natural Sciences and Engineering Research Council of Canada (NSERC) to Mark G. Carpenter (326910).