Effect Of Quercetin Supplementation On Repeated Sprint Performance And Metabolic Stress

Abstract

Repeated sprinting has been shown to induce an acute inflammatory response and increase production of reactive oxygen species (ROS) at least partly via activation of the enzyme, xanthine oxidase (XO). In vitro, XO is inhibited by quercetin (Q), a flavonol commonly found in apples, onions and other plant-based foods. PURPOSE: The purpose of the study was to determine the value of quercetin consumption on oxidative stress and inflammation induced by repeated sprint exercise. METHODS: The study was a double-blind, placebo-controlled, cross-over design. Fifteen recreationally active, young adult males with team sport experience completed two repeated sprint tests (RST) each following one week supplementation of either the placebo (P)- a 6% carbohydrate commercial sports drink, or P with 500 mg of isoquercetrin, a glycosylated and water soluble form of quercetin (Q), consumed twice a day (1000 mg/d). The RST consisted of 12x30 m sprints (S1-S12) performed every 35 sec. Sprint times were measured with a dual-beam timing gate system. The performance measure was mean sprint time for the 12 sprints. Blood samples were collected before supplementation (B0), at baseline the morning of each test (B1), immediately post-test (B2), and 1h-post (B3). Blood was analyzed for plasma XO and serum IL-6, IL-1β and uric acid (UA). RESULTS: Mean sprint times increased progressively and were significantly higher by S9 for both treatments (5.9%), however, there were no significant differences between treatments or interactions for the performance measure. Changes in XO, IL-6 and UA from pre-test to post-test were +47%, +77%, and +25% with no difference by treatment. Ninety-two percent of the IL-1β concentrations were undetectable. CONCLUSION: Repeated sprints increased xanthine oxidase activity and inflammation, but this was not attenuated by consumption of quercetin. Supported by a gift from Gatorade Sports Science Institute