In the last decade, high intensity interval training (HIIT) has been shown to be an appropriate alternative to moderate-intensity, continuous exercise for improving cardiorespiratory fitness. HIIT protocols typically result in high blood lactate (La) levels. However, accumulated lactic acid is a potent metabolic stimulus, which plays a major role in the control of physiological adaptations. Therefore, it may be essential for improvements in endurance performance. The literature indicates that there is a strong positive relationship between maximum oxygen consumption (VO2max) and La production. PURPOSE: To investigate changes in La levels after 4 weeks of HIIT program. METHODS: Blood samples were collected from five female and five male student-athletes (n= 10) (Mage=21, SD=0.95). A short-term (4 weeks) HIIT protocol used and VO2max calculated through Course-Navette Test. The instruments used for this research were an Accutrend Plus-Roche lactometer and BM-Lactate test strips (Risch-Rotkreuz, Switzerland). The analysis consisted of t student tests for paired samples in IBM SPSS v.25 (p <0.001). RESULTS: VO2max and blood La changed significantly in six participants (Pre-La M=11.65mmol/L; Post-La M=9.41mmol/L). The participants that achieved to increase their VO2max, produced lower amounts of capillary blood La. CONCLUSION: Using HIIT, our study results confirm the positive relationship of VO2max and La. The inferences of these preliminary results could be used in future, larger-scale interventions concerning ways to affect La production through the increase of VO2max using a HIIT program. Future studies should further investigate anaerobic threshold modification processes through different training programs, such as Repeated Sprint Training (RST), Sprint Interval Training (SIT) and Moderate Intensity Continuous Training (MICT). Limitations of this study include small sample size and indirect VO2max estimation. Keywords: High-Intensity Interval Training, maximal oxygen consumption, lactate