The goal of this interventional study is to compare muscle reflex function under settings of
normoxia (normal oxygen level), acute hypoxia (brief oxygen-lack) and chronic hypoxia
(long-duration exposure to oxygen-lack).
The main question is: Does the muscle reflex adapt to chronic hypoxia?
Young, healthy participants will complete light-to-high intensity cycling exercise with and
without suppression of the muscle reflex. Suppression of the muscle reflex will be via spinal
administration of the opioid Fentanyl. In the control condition, saline will be administered
into the spinal space. Participants will complete control (saline) and experimental
(Fentanyl) exercise conditions at sea-level (Kelowna, BC, Canada) breathing room air and
whilst breathing a lower fraction of oxygen (acute hypoxia). Thereafter, participants will
complete the exercise test after living at high altitude (White Mountain, CA, USA) for 2
weeks whilst breathing room air (chronic hypoxia) and breathing a higher fraction of oxygen
(restored normoxia).