Dissertation Defence: Neuromuscular adaptations with acute and prolonged exposure to hypoxia

Christina D. Bruce, supervised by Dr. Chris McNeil, will defend their dissertation titled “Neuromuscular adaptations with acute and prolonged exposure to hypoxia” in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Kinesiology.

An abstract for Christina D. Bruce’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 exams.

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ABSTRACT

When the availability of oxygen within the atmosphere is reduced (i.e., hypoxia) there are numerous adaptations that take place within the human neuromuscular system. With advancements in techniques, there is still much to discover regarding the contractile properties of skeletal muscle and how these change with the duration of exposure to hypoxia. Additionally, it has been established in male participants that the intrinsic fatigability of skeletal muscle is exacerbated with acute hypoxia and recovers following acclimatization to high altitude; however, it is currently unknown how acute and prolonged exposures to hypoxia influence muscle fatigability of females. Therefore, the studies within this dissertation have utilized external electrical stimulation of the human neuromuscular system to determine if muscle contractility and fatigability changes with acute and prolonged exposures to hypoxia. When simulating high altitude at sea level, a two-hour exposure to hypoxia led to increased contractile speeds and a rightward shift to the torque-frequency relationship of the dorsiflexors. Post-activation potentiation of the quadriceps muscle was not affected by simulated hypoxia at sea level, or after sojourning to high altitude (3800 m) for 1-2 and 11-13 days. However, potentiation of the maximal compound muscle action potential increased with altitude for males following 11-13 days at 3800 m and remained unchanged in females. For male participants, quadriceps fatigability was exacerbated by 1-2 days at altitude and did not recover following acclimatization of 11-13 days. In contrast, fatigability was unaffected by high altitude for females. These findings contribute to our collective understanding of how the neuromuscular system acclimatizes to hypoxia, and highlight the need for more research regarding female physiology at high altitude.