Abstract: The present investigation was undertaken to examine the changes in Ventilation (VE), plasma Potassium (k+) and Lactate (La) concentration during incremental exercise. Fifteen normal athletes men performed an incremental cycle ergometer exercise to extreme fatigue. Antecubital venous blood samples were taken at the end of each step and exercise onset. The VE and plasma k+ and La concentration were measured from blood samples in every step. We investigated linear regression analysis of the slopes of the ventilation, plasma k+ and La levels vs workload during incremental exercise. Our findings showed that VE and plasma k+ and La concentration proportionally increase during incremental exercise, but an inflection see in the curves. This study demonstrated that inflection on the plasma La plot occurs earlier than break points on VE and plasma potassium plots during incremental exercise.