| Summary: | Quercetin is a flavonoid found in commonly consumed fruits and vegetables that has exhibited powerful antioxidant and anti-inflammatory properties in rodents and in vitro. In humans, the ergogenic effects of antioxidant supplementation on exercise performance and adaptations are still equivocal and need to be further investigated. A powerful antioxidant such as quercetin may inhibit the high levels of oxidative stress associated with the high volume and intensity of exercise training seen with trained individuals. There have been equivocal findings thus far regarding the ergogenic effect of either acute or chronic supplementation of quercetin on exercise performance.
PURPOSE: To determine the effect of 28 days of daily quercetin supplementation on cycling time trial performance and the associated exercise performance variables.
METHODS: Thirteen trained cyclists (VO2peak 58.8 ± 3.9 ml/kg/min) were recruited for this study from the University of Texas at Austin and the local Austin, Texas community and participated in this placebo controlled, randomized, crossover designed study. After initial assessment of baseline data (VO2peak, lactate threshold, and two familiarization time trials), participants began daily supplementation of either an antioxidant supplement containing vitamins and quercetin (Q-VIT: 1000mg quercetin, 820mg Vitamin C, 40mg Vitamin B3) or the same vitamin supplement without quercetin (VIT: 820mg Vitamin C, 40mg Vitamin B3). A simulated time trial using an electromagnetically braked cycle ergometer in which subjects had to complete a set amount of work (kJ) as fast as possible was performed on the last day of supplementation. Measured performance variables included: time to completion, average power output, average oxygen consumption (VO2), Respiratory Exchange Ratio (RER), gross mechanical efficiency (GE), heart rate (HR), and rating of perceived exertion (RPE).
RESULTS: Quercetin had no effect on HR, RER, power output, or RPE. There was also no difference in time to complete the time trial between treatments. However, an approximately ~2% higher, but not significantly different, VO2 during Q-VIT supplementation significantly lowered the GE compared to VIT (Q-VIT: 20.49 ± 0.26 % and 19.94 ± 0.33 %; VIT: 20.9 ± 0.24 % and 20.37 ± 0.33 %; p < .01) at 15 and 30 min respectively.
CONCLUSION: Chronic supplementation for 28 days with a quercetin based antioxidant supplement lowered cycling gross efficiency in well trained cyclists, but it did not affect performance time. The results of the current study suggest that chronic supplementation with quercetin does not influence aerobic exercise performance in well trained athletes. === text
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