Rhythm watches your own log for two things: a lift flat at the same weight for several sessions, and four weeks of sustained high training volume.
The first signal is a lift that has stopped moving. Rhythm works out an estimated one-rep max for each lift from the weight and reps you record, and when three sessions in a row land inside the same narrow band — within about 2.5% of each other — it calls that flat. It waits until you have at least twelve logged sessions before it uses the word at all, because three sessions out of five is noise, not a pattern.
The second is volume that has stayed high for a month. Rhythm adds up your weekly training volume, and if your average over the last four weeks sits at 90% or more of your biggest week in the last eight, that is a sustained stretch. It needs at least eight logged workouts before it can tell.
When either one fires, the suggestion has the same shape: about 10% off your working weight, or a set or two fewer, for a week.
Coaches watch a third thing — effort creeping up at the same weight, where the set that used to leave you two reps short now leaves you none. Rhythm does not track it. Logging reps in reserve is not in the app today, so plateaus are read from the weight and reps you record instead. We would rather tell you that than let the picture look complete when it is not.
No study fixes three sessions, or 2.5%, or 90%. We looked, and found no peer-reviewed rule for spotting a stall from logged sets alone. Those thresholds are our judgement, set slow enough to ride out normal week-to-week noise, and what would prove them wrong is simple: if they call a deload for people who did not need one, or stay quiet while people stall, they are wrong and we will change them.
An easier week is still a training week. A walk, some mobility, a lighter session on the same lift — all of it counts.