The physical training induces positive organism adaptations leading to the improvement in the sport performance. However, a constant disequilibrium between loads of physical effort versus time of recovery can diminish the incoming performance, this phenomena is known as overtraining. The beginning of this process is called overreaching, characterized like a chronic sensation of fatigue, proceeding from an increase in the levels of oxidative stress. Several methods described in literature are able to demonstrate the levels (enzymatic and non-enzymatic system) of the exercise induced stress. Our objective in the present work is to demonstrate a new methodology to measure the redox potential status (mV) using a platinum filament as the work electrode, and Ag/AgCl as reference electrode. We used a pool of plasma of physical active subjects (n=30, males, age 18 the 25), dissolved in PBS (phosphate buffer 0,05M plus NaCl 0.9%) as sample. The potential decreasing measured in the plasma samples were correlated with the levels of oxidative stress and antioxidant status of plasma. Our data demonstrated the voltage diminishment correlated with the plasma increasing volume, using 1 mL of sample (100-500 uL, r=-0,99078). In the same way the voltage diminished with the addition of antioxidant substances like: ascorbic acid (0,002-0,010 mg/L, r=-0,99700), uric acid (0,001-0,005 mg/L, r=-0,99099) and billirubin (0,01-0,05 mg/L, r=-0,99469). Moreover, this diminishment was correlated with the decrease of the plasma lipid peroxidation susceptibility (lag phase) using the fluorimetric method previous described (Cervatto et. al, 1999). This method consists in induction the lipid peroxidation using CuSO₄ 500 uM. Finally, the effect of the O₂ dissolved in the sample was tested, and the two resulting curves (with and without O₂) are parallel, not intervening in the method. These results indicated that the presented electrode can be used as a tool to quantify the physical exercise oxidative stress in human and animal models.