Hypoxia and standing balance

Purpose Standing balance control is important for everyday function and often goes unnoticed until impairments appear. Presently, more than 200 million people live at altitudes > 2500 m above sea level, and many others work at or travel to these elevations. Thus, it is important to understand how hypoxia alters balance owing to implications for occupations and travelers. Herein, the influence of normobaric and hypobaric hypoxia on standing balance control is reviewed and summarized. As postural control relies on the integration of sensorimotor signals, the potential hypoxic-sensitive neurophysiological factors that contribute to balance impairments are also reviewed. Specifically, we examine how hypoxia impairs visual, vestibular, and proprioceptive cues, and their integration within subcortical or cortical areas. Methods This systematic review included a literature search conducted via multiple databases with keywords related to postural balance, hypoxia, and altitude. Articles (n = 13) were included if they met distinct criteria. Results Compared to normoxia, normobaric hypoxia worsened parameters of standing balance by 2-10% and up to 83 and 240% in hypobaric hypoxia (high-altitude and lab-based, respectively). Although balance was only disrupted during normobaric hypoxia at FIO2 < similar to 0.15, impairments consistently occurred during hypobaric hypoxia at altitudes > 1524 m (similar to FIO2 < 0.18). Conclusion Hypoxia, especially hypobaric, impairs standing balance. The mechanisms underpinning postural decrements likely involve alterations to processing and integration of sensorimotor signals within subcortical or cortical structures involving visual, vestibular, and proprioceptive pathways and subsequent motor commands that direct postural adjustments. Future studies are required to determine the sensorimotor factors that may influence balance control in hypoxia.

Automated summary

This review examines the impact of hypoxia on standing balance control, revealing that hypoxia, especially hypobaric, impairs standing balance. This impairment may be due to alterations in the processing and integration of sensorimotor signals, affecting visual, vestibular, and proprioceptive pathways, as well as motor commands for postural adjustments. Further research is needed to identify sensorimotor factors influencing balance control in hypoxic conditions.