BACKGROUND:Proanthocyanidin,a kind of grape seed extract(GSE),has the effect of anti-oxidation and elimination of free radicals.Research finds that increase of free radicals in skeletal muscle and active oxygen in other forms induced by exercise is one of the important causes of the injury and fatigue of skeletal muscle. Supplement of antioxidant can inhibit this kind of change and improve motor ability. OBJECTIVE:To study the anti-fatigue effects of proanthocyanidin. DESIGN:A completely randomized controlled experimental study taking experimental animals as the subjects. SETTING:A toxicological department of a provincial center for disease control and prevention. PARTICIPANTS:The experiment was completed in the Department of Toxicology,Jiangsu Center for Disease Control and Prevention from September to December 2001.Male mice of Kunming strain and common grade[certification number:SCXK(Su) 2002-0011;certification number of environmental equipment for experimental animal:SYXK(Su) 2001-0004]were purchased from the Experiment Animal Center of Chinese Pharmacological University.The 120 mice were randomly divided according to body mass into control group and 3 experiment groups, namely,low-,medium-and high-dose GSE groups,with 10 mice in each group.The mice in the 3 experiment groups received oral administration of GSE every day. INTERVENTIONS:The mice in the 3 experiment groups received oral administration of GSE of 1.7, 16.7 and 50.0 mg/kg body mass,respectively,while those in control group were only given twice distilled water for 30 consecutive days. After GSE treatment for 30 days,the loaded swimming time, contents of hepatic glycogen,blood lactic acid(LA) and hemoglobin were measured. MAIN OUTCOME MEASURES:Loaded swimming time, hepatic glycogen,LA and hemoglobin contents. RESULTS:The loaded swimming time of mice in experiment groups was significantly prolonged as compared with that in control group (P< 0.01),with(17.84± 8.48) and(25.80± 7.45) minutes in medium-and high-dose GSE groups,respectively.LA content after exercise in experiment groups was all lower than that in control group,with greatly significant difference between high-dose GSE group[(6.78± 2.45) mmol/L] and control group[(9.98± 1.22) mmol/L](P< 0.01).The content of hepatic glycogen after exercise in experiment groups was higher than that in control group; medium-dose GSE group[(1 244.65(177.58) mg/100 g liver mass]and high-dose GSE group[(1 383.96± 141.20) mg/100 g liver mass]differed greatly significantly from control group[(817.67(114.72) mg/100 g liver mass](P< 0.05,P< 0.01). CONCLUSION:Grape seed extract proanthocyanidin has an anti-fatigue effect.