Recording the endurance lactate concentration has for some 40 years now been considered the most sensitive parameter for identifying and differentiating the aerobic capacity in muscle metabolism. Lactate behavior or the lactate-running-speed ratio is influenced under lab conditions both by the shock absorption of the specific treadmill type, the treadmill angle of inclination, and outdoors by the ground conditions. What is decisive for both indoor and outdoor measurements is the integrative lactate behavior.