Function Threshold Power (FTP) is a measure of your cycling fitness and ability to maintain a high but manageable power output for a somewhat lengthy duration. From a physiological perspective, it’s the cycling power you produce when your lactate production has risen, leveled off, and then closely matches your body’s ability to remove lactate. This just barely keeps that lactate flooding at bay. In cycling, FTP is that grey area between the power you can sustain for a very long duration, typically an hour, and the fleeting power you can only tolerate for a couple of minutes. When you are cycling, FTP is the balance point between energy supply and demand. Specifically, FTP is the balance between your aerobic and anaerobic energy systems. When you are cycling at low intensities, you are using your aerobic system. The aerobic system uses oxygen to metabolize fuel to create the needed energy. When your aerobic system can meet the energy demands of your muscles, there’s less contribution from your anaerobic energy system.