Vitamin adjusts the energy metabolism in physical activities and is widely used as a dietary supplements to enhance exercise performance. [1-3]. Among vitamins, thiamine is an coenzyme of the pyruvate dehydrogenase (PDH) which stimulates the conversion from the pyruvate to the acetyl CoA and plays an important role in carbohydrate metabolism. It also plays a role as a coenzyme of the branched-chain decarboxylase which reacts to the physiochemical reaction of the oxoglutarate dehydrogenase and the branched-chain amino acids in the formation of succinyl CoA in the TCA cycle [4]. Decreasing the thiamine in the cell degrades enzyme activation, decreases ATP biosynthesis and causes fatigue [5]. Such a low level of thiamine in the body may degrade the exercise performance. Thiamine tetrahydrofurfuryl disulfide (TTFD), lipid-soluble thiamine, is effectively absorbed from various organs compared to the water-soluble thiamine, thiamine hydrochloride (THCL) which limits the absorption, converted to thiamine in the cytoplasm and to the phosphate ester [6-8]. A daily recommended dose of thiamine is 0.5mg/1000Kcal for a healthy adult. Therefore, thiamine may be sufficiently taken; otherwise, the energy intake would be limited or refined food would be taken too much in daily life [9]. However, it is reported that thiamine request may increase by stimulating the metabolic pathway using thiamine under continuous exercise [4]. Kaiserauer et al. [10] report that the thiamine level is low for an athlete under intensive training. Guilland et al. [11] report that vitamin deficiency in sedentary is restored to the normal range, but it is not effective for athletes after supplementing multivitamin with thiamine. Hasegawa et al. [12] propose that thiamine and riboflavin intake increase for athletes during the season compared to the off-season. Such result suggests that the athletes under continuous training may experience thiamine insufficiency. Also, if a person takes vitamin B (B₁, B₂, B₆), vitamin C and other vitamins less than one third of the recommended daily requirements, it is observed that the maximum oxygen uptake and the lactate threshold significantly decrease within 4 weeks, causing problems in the exercise performance through vitamine deficency [13]. Van der Beek et al. [14] report that the maximum oxygen uptake decreases by about 11.6% and the lactate accumulation increases by 7% as a result of deficiencies in thiamine, riboflavin and vitamin B₆ for 24 healthy male adults for more than 11 weeks. Also, Fogelholm et al. [15] announce that the erythrocyte activation coefficient significantly increases as a result of supplementing multivitamin for 42 active university students with low levels of thiamine, riboflavin and vitamin B6 for 5 weeks. However, such result is from the study involving the vitamin B complex, and for this reason it is hard to say that the effect is from thiamine alone, which calls for a study involving single intake of thiamine. Up to now, it is observed that the single supplementation of thiamine decreases fatigue in seniors and manual workers [16,17] and prolongs the duration of swimming time until exhaustion while decreasing the lactate threshold and lactate concentration [18-20]. However, Doyle et al. [21] and Webster [22] propose that the TTFD intake does not affect exercise performance. Studies observing the effect of single administration of thiamine do not reach a clear conclusion and the one week supplementation period is too short requiring investigation on the effect on long-term supplementation. Meanwhile, it is reported that regular exercise increases the PDH activation in the model exposed to diabetes and improves carbohydrate metabolism [23]. It is observed that much supplement of thiamine is effective in improving diabetic complication [24-30]; it is also confirmed that the result is related to the PDH activation, as thiamine supplementation increases the PDH activation [31]. Therefore, the thiamine supplementation suggests that it would activate PDH at the same level of regular exercise, and it is required to verify how thiamine supplementation affects healthy person.

Such results show that thiamine supplementation may prevent fatigue and increase the exercise performance, but there are insufficient studies in Korea on the effect of exercise on fatigue after taking thiamine for a long time . Also, whether the thiamine supplementation is utilized as an effective administration in improving the carbohydrate metabolism similar to endurance training needs to be verified. Therefore, this study was to observe the effect of endurance training and thiamine supplementation on anti-fatigue during exercise.

The research result shows that the glucose concentration in the blood is significantly lower in the training treatment than in the placebo treatment at 15 and 30 minutes of the training; the thiamine treatment is significantly low from 15 to 60 minutes after the exercise. It is reported that free fatty acid concentration decreases with the increase in fat-oxidation during exercise with the same exercise intensity after regular training, resulting in the decrease of the carbohydrate-oxidation and saving the muscle glycogen [33-35]. The training treatment shows decrease in free fatty acid concentration from 30 minutes to 45 minutes after the exercise; it significantly decreases 60 minutes after the exercise. Therefore, it is considered that regular training decreases carbohydrate-oxidation and glucose in the training treatment. Also, thiamine supplementation activates PDH for the thiamine treatment [36,37], catalyzing pyruvate to acetyl CoA, increasing the movement to the skeletal muscles while decreasing glucose in the blood. Such result is the same as that of Choi [38] who report a significant decrease in glucose in the blood compared to the placebo treatment during exercise when thiamine is supplemented for a week to female university students majoring in physical education. It is considered that the lactate and ammonia accumulation during exercise increases hydrogen ions and acidosis in the muscles and is known as a major cause of muscular fatigue [39,40]. The lactate concentration in blood significantly decreases during exercise in the training treatment and the thiamine treatment in the present study. Such result is the same with the research by Philips et al. [41] who report decrease in lactate concentration during cycling exercise for a month with 60% of the maximum oxygen uptake for untrained man. Meanwhile, Park and Gubbler [42] observe that the lactate production decreases after taking thiamine, and Van der Beek et al. [14] report that the maximum oxygen uptake decreases and the lactate accumulation increases by 7% as a result of vitamin deficiency including thiamine for 11 weeks among healthy men. Also, the study by Knippel et al. [18] proposes that the lactate concentration decreases during exercise with the thiamine supplementation for cyclists, which is the same with the result of the present study. Such result is in accordance with a study which states that the PDH activation decreases the lactate accumulation [43,44] and the thiamine supplementation activates PDH [31,45]. Also, it is thought that the fatigue materials decrease by effective engagement of the training treatment and the thiamine treatment in the energy metabolism process of the ammonia concentration for the same result of the lactate concentration. Increasing the glucose use in the skeletal muscles during exercise causes the liver to supply the glucose required during exercise through glycogenolysis and gluconegenesis [46]. Increasing glucagon in the blood increases the glucose excretion from the liver and the glucose use in the muscles as a result [47]. It is reported that the endurance training increases the glucagon sensitivity in the liver [48,49] but the study shows that the training treatment shows no large changes compared to the placebo treatment. However, it is found that the glucagon concentration is significantly high compared to the treatments at 15 and 30 minutes of the exercise for the thiamine treatment. Such result is the same with the report by Choi [38] which observes the glucagon concentration increase during exercise after single supplementation of thiamine. Therefore, it is considered that glucagon increases to maintain the required demand for metabolism by effectively using the glucagon in the blood through the thiamine supplementation. The insulin decreases with the increase in the period of the endurance training [50] and the repetitive endurance training is reported to decrease the insulin concentration under the same exercise intensity [51]. The study shows that the insulin concentration gradually decreases regardless of the administered material at 60 minutes after the exercise but no difference among the treatment groups. The thiamine is absorbed by the small intestine, observed in the skeletal muscles, liver, heart, kidneys and brain with a high concentration, and a continuous supply is required with the limited storage in the tissues with half life of 10 to 20 days [52]. The plasma thiamine level for a healthy person is reported between 0.018 and 0.855μmol·mg-1 [53-55] and the thiamine level is within the normal range in the resting state of the subjects. Also, it is found that the thiamine level significantly increases for all treatment groups after 60 minutes of the exercise, metabolic requirement for glucose in the later part of the exercise and the thiamine concentration. The training treatment for 4 weeks significantly decreases the thiamine concentration in rest compared to the placebo treatment. Such result is the same with the study by Sato et al. [56] which observes the thiamine concentration decrease for the training of swimming athletes and by Kaiserauer et al. [10] who report that the thiamine concentration decreases for the training of athletes. Such result suggests that exogenous thiamine is required for continuous training. Soares [57] reports that the trained group shows higher serotonin concentration than the non-trained group during rest for the general public. It is proposed that the serotonin concentration increases in rest after the pilates treatment for 12 weeks [58]. The study also shows a significantly high concentration of serotonin during rest after 4 weeks of the bicycle ergometer training in the training treatment compared to the placebo treatment. It is reported that increasing serotonin in the brain after intensive exercise for a long time causes central fatigue [59] and the serotonin concentration increase in the brain is inhibited by continuous training [60]. However, Pitsiladis et al. [61] propose that the serotonin in the brain is not a predictor of the serotonin level in the central fatigue and brain; and it is established that the interpretation of serotonin in the blood has not reached a clear result. The present study shows significant increase in the serotonin concentration in the training and thiamine treatments compared to the placebo treatment after 60 minutes of the exercise. It is said that the serotonin increase in the brain during endurance exercise is caused by the tryptophan increase in the condition of high free fatty acid concentration in the blood [62]. The study shows low lactate and ammonia concentrations in the blood and the rating of perceived exertion in the training and thiamine treatment compared to the placebo treatment after 60 minutes of the exercise, and free fatty acid does not increase. Therefore, it is expected that the serotonin concentration in the blood is not the same with the brain, and more specific studies are required in the future. The training and thiamine treatments shows significant decrease in the rating of perceived exertion than the placebo treatment. Boyle et al. [63] observe that the decrease of the glucose concentration in the brain affects the rating of perceived exertion. Therefore, the reason why the rating of perceived exertion is low is that sufficient amount of glucose is supplied to the central nerve system by effectively using the glucose from the thiamine supplementation for the thiamine treatment.

The combination of such results confirms that the thiamine supplementation for more than 4 weeks brings significant effect on the energy metabolism during exercise, decreases the lactate and ammonia concentration and the rating of perceived exertion; it also positively affects anti-fatigue and may be used as an effective treatment similar to the endurance training. The endurance training with the thiamine supplementation or the complex treatment of glucose or fructose with different glycemic index may be provided as the basic data for the future studies which may verify the effect of biological activity.