Introduction: The use of incremental exercise tests (IET) to evaluate the individual’s acute responses is an essential tool in Physical Activity Science.
 Objective: This paper aims to analyze the behavior between biochemical and physiological variables as aerobic-anaerobic transition indicators during two incremental exercise tests, which measure the maximum oxygen uptake in healthy subjects.
 Methodology: The sample consisted of two individuals, who were thirty-three and twenty-five years old, respectively. During the execution of the tests, the following materials and tools were used: a portable glucometer, a portable lactometer, reactive tapes, a treadmill, a stationary Cycle Ergometer Monark®, a heart rate monitor Polar®, a gas analyzer, software Breeze®, a computer, tools for recording data, and a pencil.
 Results: the high inverse correlation between the Glycemic index and VO2 (r: -0,853) and the Glycemic and CO2 (r: -0,851) are notable. Moreover, the detection of thresholds for each subject through blood lactate invasive and non-invasive methods, such as heart rate (HR), is also shown.
 Conclusion: A clear explanation of Respiratory Quotient (RQ) behavior is given during the Cycle-ergometer test, concluding that this type of protocol is safe for the group under study and that the validity of the results is in accordance with theoretical expectations.