ERG mode is also called "locked power mode". When ERG mode is turned on and the target power is set, if the rider is slow pedaling, the cycling trainer will automatically increase the resistance to maintain the rider's target power output. If you pedal fast, the trainer will automatically reduce resistance, like a cruise. However, be aware that ERG mode can cause damage to your body and knees if your abilities fall short of the target power, so it is not recommended for novices to use it often.