The study looked for the impact caused by a treadmill running test on different biomarkers, changes in the cardiovascular system, and correlation between IL-12 and performance. The heatmap showed a correlation of 1.0 (P = 0.00278) between IL-12 and VO2 in the respiratory compensation time and of 0.943 (P = 0 .0167) between pre-exercise IL-12 and the time to reach maximal effort, with the same correlation coefficient and P-value between pre-exercise IL-12 and the distance covered, and pre-exercise IL-12 and the test time. Post-exercise IL-12 presented a correlation coefficient of 0.9 (P = 0.0167) with the heart rate of the respiratory compensation point. A breakpoint for both the double product and heart rate was observed between minutes 2 and 3 of the test, both measurements being more acute than the anaerobic threshold and the respiratory compensation point, and even that breakpoint for systolic blood pressure. The average percentage change in heart rate and the double product obtained the same value (213%). In treadmill running tests with incremental load, the heart rate breakpoint and the double product are the most sensitive and acute markers of the stress level, and the production of IL-12 depends on the intensity and duration of the exercise, which may correlate with performance.