Multiplying effort by duration to estimate internal load
Session RPE load is a simple way to quantify how hard a training session was internally. After a session, the athlete rates overall exertion on a perceived-effort scale, and that rating is multiplied by the session duration in minutes. The product gives a single number in arbitrary units that reflects both how hard and how long the session was. The approach was popularized by Carl Foster as a low-cost training-load monitor.
Because it captures the athlete's own response rather than only the external work done, two people doing the same workout can register different session loads, which is often the point: it reflects internal stress.
Tracking trends, weekly load, and limits
Summed across a week, session RPE loads give a weekly training load that can be watched for sharp spikes, since rapid increases in load are associated with higher injury risk in some monitoring research. It is a proxy, not a precise physiological measurement, and the rating should ideally be collected a short while after the session and consistently.
This is general educational information about a monitoring tool, not medical advice. For interpreting load and injury risk, work with a qualified coach or clinician.