ingestion of some amino acids has presumable roles in performance improvement in athletes.[13 ] among them , -alanine supplementation has been suggested to improve performance during high - intensity exercises . on the other hand , it has been shown that large amounts of h are produced in the muscles during high - intensity exercise and result in ph reduction . there are many cellular ph buffers defend against exercise - induced acidosis , which include phosphocreatine , inorganic phosphates and histidine - containing dipeptides . carnosine ( -alanyl - l - histidine ) is the main histidine - containing dipeptide in humans . additionally , hill et al . and harris et al . , showed that 28 days of -alanine supplementation increased intramuscular levels of carnosine by nearly 60% . antioxidant function , muscle contractility regulation , and ph buffering , are the possible physiological roles of carnosine in skeletal muscle . thus , the possible role of carnosine could be prevention of skeletal muscle acidity in improving exercise performance . prolonged exercise can result in oxidative stress and muscle fatigue , which may be prevented by carnosine due to its antioxidative properties . on the other hand , -alanine administration could increase carnosine content of skeletal muscles by 4080%.[1719 ] increase of carnosine concentrations in muscle results in altered buffering capacity,[1819 ] and thus affects performance . furthermore , some studies have shown that carnosine acts as a ca sensitizer for the sarcomeres in muscles[2021 ] and thus could prevent fatigue . however , synthesis of carnosine in muscle is limited by the availability rate of -alanine , which can be overcome by -alanine supplementation . although it has been estimated that carnosine is responsible for nearly 10% of the total buffering capacity in human muscle there are few studies on -alanine supplementation and its possible effects on endurance exercise ; therefore , the purpose of this study is to assess the effects of -alanine administration on vo2 max , time to exhaustion and lactate concentrations in male physical education students . these students were fit ( bmi<25 ) and active ( physical activity2 hr / d ) , but not involved in professional sports . participants age , weight and height were 21.10.7 years , 71.88.8 kg and 1787 cm , respectively , for -alanine ( n=20 ) group and 21.91.5 years , 74.98.3 kg and 1805 cm for placebo group ( n=19 ) , respectively ( ns ) . before initiating the study , all participants were informed of all procedures of the study and signed an informed consent . none of the participants had ingested -alanine , or any other nutritional supplements , for a minimum of 3 months before the initiation of the study . participants were asked to abstain from exercise 24 h before trial initiation and to maintain their current physical activity and dietary patterns . after pre - testing , the participants were randomly assigned to one of the two groups : a ) -alanine ( 2 g / day ) , b ) placebo ( 2 g dextrose per day).the supplements had the same appearance , and ingested four times per day for 42 consecutive days before post - testing . all participants completed all experiments , and there were no complaints of side effects of the supplements . participants were supplemented orally for 6 weeks with either -alanine ( ajinomoto , usa , inc ) or placebo ( dextrose ) . the study was approved by the ethics committee ( esfahan sport medicine association , iran ) . supplements were provided in capsules of 400 mg and were administered each day as five divided single doses , with at least 2 h in between ingestions . venous blood samples were obtained from all participants between 5:00 and 6:00 p.m , after intensive endurance exercising , at the baseline and after intervention . all measurements were done before the start of the supplementation ( pre ) and after the intervention ( post ) . prior to and following the supplementation protocol , participants performed a continuous graded exercise test ( gxt ) on an electronically braked cycle ergometer ( lode , the netherlands ) to determine vo2 max and time to exhaustion ( tte ) . for each gxt , the primary power output was set at 30 w and elevated 30 w every 2 min until the participant could not maintain the required power output at a pedaling rate of 70 rpm due to fatigue . plasma samples were obtained for the determination of plasma lactate and glucose concentrations immediately prior to each gxt and 2 min post - exercise . glucose and lactate were analyzed using ysi auto - analyzer ( yellow springs , oh ) . statistical analyses were conducted using the statistical program for the social sciences ( spss version 13 , inc , chicago , il ) computer software package . paired t test was used to analyze before and after test data for each group differences . table 1 shows the mean  sd values of exercise performance indices for the pre - and post - supplementation . supplementation with -alanine demonstrated a significant increase in vo2 max ( p<0.05 ) . on the other hand , tte and lactate concentrations decreased after 6 weeks of supplementation with -alanine ( p<0.05 ) . the placebo group showed a significant increase in lactate concentrations ( p<0.05 ) , but a non significant increase in tte . comparison of exercise performance indices , pre - and post - supplementation ( mean sd ) the post - exercise concentrations of plasma lactate were significantly higher ( p<0.05 ) than baseline in two groups . however , the post - exercise concentrations of lactate were significantly lower ( p<0.05 ) during the alanine supplementation compared to the placebo group . dietary intake before each trial was similar for energy and macronutrients [ table 2 ] . the findings of our study suggest that supplementation with -alanine may improve the endurance exercise performance as measured by the vo2 max , tte and plasma lactate concentrations . , showed that supplementation with creatine + -alanine resulted in significant increases ( p<0.01 ) in muscle carnosine content . the increased muscle carnosine content was accompanied with an improvement in vo2 max and tte in response to a maximal graded exercise test performed on a cycle ergometer . another study demonstrated that supplementation with both -alanine and creatine improved cycling performance ( tte ) . they concluded that this was due to h buffering by carnosine during this transitional period . our data demonstrate that the significant improvements in the performance indices with -alanine supplementation were due to ph reduction . the improvement in tte seen in the placebo group participants might be due to the encouragement provided by our staff and also the participants psychological status . also , the findings of the present study might have been influenced by the fluctuations in the skeletal muscle response to oral supplementation with -alanine . our data suggest that supplementation with -alanine may delay the onset of fatigue and thus improve performance during incremental cycle exercise in men . the glucose concentrations did not change significantly in our study , due to different individual response and insufficient dose or duration . the participants in this study , however , were male physical education students rather than untrained participants . however , according to the hypothesis , -alanine supplementation would prevent the drop in intracellular ph during high - intensity contractions and result in less circulating acidosis finally due to elevation of myocellular carnosine content . furthermore , several studies have shown the importance of ph regulation on performance during endurance exercise , by a pre - exercise alkalosis intervention . this suggests that the difference between groups is related to the presumable enhancement of muscle carnosine content . future studies should examine muscle carnosine levels along with vo2 max and plasma lactate concentration during strenuous exercise with variable quantities of -alanine supplementation also , further investigations are necessary to determine the effects of -alanine supplementation during more prolonged and submaximal exercise . it can be concluded from this study that -alanine administration can reduce acidosis during high - intensity exercise and thus can improve exercise performance in endurance athletes . also it is found that six weeks of supplementation with -alanine at the mentioned prescribed dose did not result in significant changes in glucose concentrations .