Doctoral Examination: The influence of hypoxia on sensorimotor function during upright stance

Mathew Debenham, supervised by Dr. Brian Dalton, will defend their dissertation titled “The influence of hypoxia on sensorimotor function during upright stance” in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Kinesiology.

An abstract for Mathew’s dissertation is included below.

Examinations are open to all members of the campus community as well as the general public.

Registration is not required for in-person defences.

---

ABSTRACT

The overall aim of this dissertation is to advance our understanding of how hypoxia influences postural control and sensorimotor function. The objectives included: 1) Identifying 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 – FIO2 = ~0.12) on the vestibular control of balance, and subsequent normoxic recovery (10 min); 3) Determine the effects of four hours of normobaric hypoxia (FIO2 = ~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; ~FIO2 < 0.18), while balance impairments during nomobaric hypoxia only occurred at altitudes >2500 m (FIO2 < ~0.15). Chapter 2 addressed objective 2 and determined that ~55 min 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 Chapters 3 and 4 determined that vestibular-evoked balance responses and tendon-evoked inhibitory reflexes were reduced following two hours of normobaric hypoxia and remained lower at four hours compared to normoxia (~0.11 FIO2). Chapter 5 demonstrated that cutaneous reflexes evoked via the sural nerve were unchanged by two and four hours of normobaric hypoxia compared to normoxia. The findings from 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.