Background: Consumption of carbohydrates before physical activity, by maintaining glycogen, leads to better performance and less muscle damage. This study aimed to compare the effect of glucose (glu) and fructose (fru) intake before physical activity on lactate and lactate dehydrogenase (LDH) levels in non-athlete teen boys.

Materials and Methods: The present study was a clinical trial with a single-blind crossover experimental group. 10 male students (17-19 years) in Zahedan, were purposefully and accessibly voluntarily selected. Stage1, take a blood sample after 30 minutes of glu uptake (75g/350ml water) then do EE (Running on a treadmill with a slope of 5% and an intensity of 82% of maximum heart rate) and after 5 minutes, the second blood sampling was performed. After 10 days, the stage2 was performed for fru. In both stages, lactate and LDL levels were measured before and after EE. Data were analyzed using analysis of variance with repeated measures and independent t-test. Statistical analysis was performed using spss 19 software (P≤0.05).

Results: The results showed that lactate increased after EE after glu (P˂0.001) and fru (P˂0.001) and between lactate levels after EE after glu and fru, no difference was observed (P=0.062). There was no difference in LDH after EE after glu (P=0.332) and fru (P=0.282) and LDH levels after EE after fru compared to after glu intake increased (P=0.032).

Conclusion: There is no significant difference between taking glu and fru supplements before EE on lactate levels and fatigue caused by it, but glu consumption compared to taking fru before EE can prevent possible muscle damage.