Reps in Reserve (RIR) is a form of autoregulation similar to Rate of Perceived Exertion (RPE).

RIR tends to be more advanced since it requires some training experience with a specific exercise. It is generally more accurate for gauging the intensity of an exercise set, as it estimates your proximity to failure.

For example, if you are programmed to perform the bench press with an RIR of 3, you would perform the exercise until you have 3 reps left before reaching failure.

If you have any questions, please feel free to reach out. Until then, happy training!