An ERG file contains information about a cycling workout that is used by various cycling training programs, such as RacerMate CompuTrainer, Hurts Ergo, Rouvy, and Trainer Road. It stores information about a power cycling workout, such as the duration, distance, average speed, calories burned, description, and post-activity comments. ERG files can only store power cycling data, whereas heart rate and pace cycling data are typically stored in .FIT files.

ERG files may be created by a variety of workout programs, including RacerMate CompuTrainer, GoldenCheetah, and TrainingPeaks. ERG files may then be imported by a large number of programs, such as PerfPRO Studio in Windows, TrainerRoad in macOS, Hurts Ergo in iOS, and TrainerRoad in Android.