Acute Effects Of Single-Dose Flavonoids Supplementation On Some Endurance Performance And Physiological And Biochemical Parameters

Purpose:Endurance exercise leads to the over-production of free radicals and results in oxidative stress,then impairs endurance performance.To cope with it,it is common that supplementation with exogenous antioxidants.Among some common-used antioxidants,flavonoids aroused more and more focus in these years."R&E"is a functional drink developed by a company in Hangzhou,China,after a preliminary study,whose main ingredient is flavonoids.The usage and dosage of R&E is two doses of 100 mL（containing 147.4 mg of flavonoids）within 30 min before exercise,which is in accordance with the literature recommendation of"supplementation with no more than 300 mg of polyphenols within 2 h（1 h is better）before exercise to enhance endurance performance",but has not been validated by empirical studies.Therefore,this study aimed to verify the efficacy of R&E in enhancing endurance performance and to investigate the acute effects of single-dose flavonoids supplementation on some physiological and biochemical parameters to endurance exercise in college students.This study also verified the effectiveness and feasibility of acute,low-dose flavonoid supplementation strategies.Methods:Twenty volunteers（18 males,2 females,age 22.0±2.1 yrs,height174.9±5.7 cm,body mass 68.2±4.5 kg,maximal oxygen uptake 50.7±7.0mL/min/kg,maximal aerobic power 281.8±40.2 W）participated in one maximal oxygen uptake(VO_2max)test and three time-to-exhaustion cycling（TTE-75%）tests at a constant intensity of 75%maximal aerobic power（MAP）in a randomized,double-blind,crossover design.Three different nutritional interventions（no-supplement,147.4 mg flavonoids beverage or placebo）with7 days washout period at least were utilized within 30 min before TTE-75%tests.The indicators of VO_2maxtest were VO_2maxand MAP,then chose75%MAP as the mechanical intensity of the follow-up TTE-75%tests.The indicators of TTE-75%test were time to exhaustion（TTE）,mean pedaling frequency(RPM_mean),mean heart rate(HR_mean),mean rating of perceived exertion(RPE_mean),peak oxygen uptake(VO_2peak),peak blood lactate(BLa_peak),serum creatin kinase（CK）,salivary cortisol（Sal-C）,serum malonaldehyde（MDA）and superoxide dismutase（SOD）.Statistical analysis was finished by SPSS 24.0 and the data was shown as Mean±Standard Deviation（M±SD）.One-way Repeated Measures ANOVA was chosen to analyze the pre-test body mass,salivary cortisol and blood lactate of participants,and the intergroup changes of HR,RPE,VO₂ and BLa at different time points.Other indicators were analyzed by Canonical Correlation Analysis followed by Multivariate ANOVA.Results:The VO_2maxand MAP of 20 participants were 50.7±7.0 mL/min/kg,281.8±40.2W.No significant differences between 3 groups（no-supplement,flavonoids,placebo）were found in TTE（12.0±3.9,12.3±4.8,12.4±3.6 min）,RPM_mean（74.5±4.2,76.7±5.9,75.4±4.8 rpm）,HR_mean（162.8±8.6,165.6±6.8,165.2±7.9 bpm）,RPE_mean（15.4±1.0,15.4±1.1,15.5±1.0）,VO_2peak（4.5±0.7,4.5±0.7,4.4±0.7 L/min）,BLa_peak（10.5±2.0,10.4±1.8,10.5±2.0mmol/L）,Sal-C（7.5±1.7,8.0±1.6,7.1±1.5 nmol/L）,CK（55.1±25.1,53.7±20.5,53.3±23.0 ng/mL）or MDA（5.0±1.0,4.8±1.1,4.5±1.1 nmol/L）,but in the concentration of SOD（133.1±36.4,158.2±38.8,152.9±37.2 ng/mL）,whereas the significant difference only existed between no-supplement group and flavonoids group.Conclusion:According to the R&E product provided by a company in Hangzhou and its usage and dosage（2 doses of 100 mL containing 147.4 mg of flavonoids within 30 min before exercise）,it did not enhance endurance performance,reduce the degree of physiological and biochemical responses to endurance exercise,but it significantly increased the content of endogenous antioxidant enzymes,SOD,compared with no supplementation.It is recommended that endurance athletes and enthusiasts should be cautious to use R&E products.