| Summary: | 碩士 === 國立臺北護理健康大學 === 運動保健研究所 === 106 === PURPOSE: The purpose of this study was to investigate the effect of normobaric hypoxia on cognitive function and cerebral blood flow distribution during a 20-km cycling time-trial. METHODS: Using a crossover and counter-balanced design, eleven endurance-trained cycling or triathlon athletes (age: 21.8 ± 1.2 years, VO2max = 59.6 ± 1.3mL/kg/min) were assigned to complete two different trials in randomized orders, including 1) normoxia (N; FiO2 = 20.9%) and 2) hypoxia chamber (H; FiO2 = 16.5%). The subjects cycled 20 km time-trial (TT), and the heart rate (HR), oxyhemoglobin saturation (SpO2) and rating of perceived exertion (RPE) were recorded periodically. Reaction speed test was measured at 9 and 18 km during the ride. Saliva samples were collected at baseline and immediately after exercise for cortisol measurements. The prefrontal cerebral blood flow was continuously measured using NIRS during 20 km TT. Two-way ANOVA with repeated measure was used to compare the differences for all measurements. RESULT: 1) When exercising under hypoxia condition, SpO2 showed a significant decrease and salivary cortisol displayed a significant increase. 2) Exercise performance (HR, SpO2, RPE and exercise time) and the blood flow in prefrontal cerebral tissue were not significantly different during 20 km TT between the two trials. 3) Reaction speed was significantly increased during 20 km TT. However, the enhancement of reaction speed at normoxic exercise was significantly greater than that at hypoxic exercise. CONCLUSION: This investigation demonstrates that despite increases in oxygen deficiency and stress hormone under hypoxia, the exercise performance and prefrontal blood flow were not affected by normobaric hypoxia environment. However, the inducible effect of exercise on promoting reaction speed was reduced in hypoxic conditions.
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