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Debenham, Mathew Ian Bergens

University of British Columbia

The overall aim of this dissertation is to advance our understanding of how hypoxia influences postural control and sensorimotor function. The objectives include: 1) Identify the influence of both normobaric and hypobaric hypoxia on standing balance; 2) Examine the influence of normobaric hypoxia over one hour (fraction of inspired oxygen - F₁O₂ = ~0.12) on the vestibular control of balance, and subsequent normoxic recovery (10 min). 3) Determine the effects of four hours of normobaric hypoxia (F₁O₂ = 0.11) on three sensorimotor reflexes (vestibular, Golgi tendon organ, and cutaneous) during standing balance. A systematic literature review (Chapter 1) addressed objective 1 and found that hypobaric hypoxia induced larger and more consistent increases in postural sway at all tested altitudes (>1524 m; ~ F₁O₂ < 0.18), whereas balance deficits during nomobaric hypoxia only occurred at altitudes >2500 m (F₁O₂ < ~ 0.15). Chapter 2 addressed objective 2 and determined that ~one hour of normobaric hypoxia reduced whole-body vestibular-evoked balance responses in the time and frequency domains. Vestibular-evoked balance responses remained blunted into normoxic recovery and had greater, more consistent reductions when visual cues were present compared to occluded. Chapters 3-5 addressed objective 3. Specifically, both Chapter 3 and 4 determined that vestibular-evoked balance responses and tendon-evoked inhibitory reflexes were reduced following two hours of normobaric hypoxia (~0.11 F₁O₂) and remained lower at four hours compared to normoxia. Chapter 5 demonstrated that cutaneous reflexes evoked via the sural nerve were unchanged by two and four hours of normobaric hypoxia compared to normoxia. This dissertation will expand the current understanding of how hypoxia influences sensorimotor function and standing balance, and potentially aid in devising strategies to improve postural control at high altitude.

Text

2023-03-16

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/83924

Kinesiology

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/4.0/