Log both numbers. The gap between them is the signal.

The set that told you nothing

The bar's loaded to 82.5%, and it's the same 82.5% you pulled in week one of the block. Same shoes, same belt, same third set of five. The rep speed is off. Not failed, not a grinder, just slower off the floor in a way you clock for half a second and forget by the time the plates are back on the rack.

So you log the weight. You log the reps. You close the app.

Eight weeks later the block stalls, and you go back through the log looking for the week it started. Every deadlift entry says the same thing. 82.5%, five reps, done. The number that would have explained the stall was in your body that Wednesday, and it never made it into a field.

The drift map

Percentages record what you planned to lift. RPE records what it cost you. Put both on every working set for a full block and a third thing appears that neither field produces on its own: the drift map, the running gap between prescribed load and actual cost, dated, and attached to a specific movement.

A percentage is a promise your program made about your capacity, calculated off a max you tested weeks ago under conditions you no longer remember. The RPE is the invoice. One number is a plan, the other is a measurement, and the interesting information lives in the distance between them.

When the invoice comes in consistently higher than the promise on one lift and not the others, that's not a bad day. That's a fatigue signal with a timestamp. Two fields. No extra equipment, no extra sets, maybe four seconds of thumb work per set.

Why "RPE or percentages?" is the wrong question

Ask a serious lifting forum whether to run RPE or percentages and you'll get a real argument with real people on both sides. The percentage camp says autoregulation lets you talk yourself into a lighter day. The RPE camp says a fixed percentage ignores that you slept five hours and ate at a gas station. Both are correct about the other's failure mode, and the r/BarbellMedicine thread that keeps resurfacing on this, "Am I wrong, or is RPE not actually a form of progression?", is asking something sharper than the usual version: whether RPE is a progression scheme at all.

It isn't one. It was never supposed to be. RPE is an instrument reading, and a percentage is a prescription, and the debate only makes sense if you assume the two are competing for the same slot in your log.

They aren't. Most tracking apps put them in the same slot anyway, which is where the confusion comes from. You pick load-based logging or you pick effort-based logging, the interface nudges you into one, and the field you didn't pick is simply absent from your training history forever.

What the research actually supports

The reps-in-reserve version of the RPE scale that most lifters use came out of Zourdos and colleagues in 2016, in the Journal of Strength and Conditioning Research. It's not the old Borg cardio scale rebadged. It asks a specific, answerable question: how many reps could you have done. That's what makes it loggable data rather than a mood rating.

Helms and colleagues published a comparison of RPE versus percentage-1RM loading in periodized programs in Frontiers in Physiology in 2018, and the honest summary of that literature is that neither loading method has established a decisive advantage for strength outcomes when sets and reps are matched. Which is exactly what you'd expect if they're measuring different things.

The more useful finding for a lifter is older and less contested: the number of reps a person can perform at a given percentage of 1RM varies substantially between individuals and between exercises (Hoeger et al. (1990) found the number of repetitions performed at given percentages of 1RM differs across lifts/exercises. ([source](https://opensiuc.lib.siu.edu/cgi/viewcontent.cgi?article=1744&context=gs_rp))). Your 85% and your training partner's 85% are not the same stimulus. Your squat 85% and your deadlift 85% are not the same stimulus. A percentage alone can't tell you which of those you're currently dealing with. An RPE logged next to it can.

Eight weeks of deadlifts, read backwards

Take a lifter running a percentage-based block, four days, deadlifting once a week off a working max set in week zero. Say the log reads like this. Week one, top set at 82.5%, RPE 7.5. Week three, same 82.5%, RPE 8. Week five, still 82.5%, RPE 8.5, and the last rep was slow. Week seven the same load moves at an 8.5 again and the fifth rep doesn't happen.

Read the load column alone and weeks one through six are identical successes followed by one bad session. Nothing to diagnose. Read the RPE column alone and you have a lifter who felt progressively worse, with no way to tell whether that's fatigue or whether the loads were climbing. Read them together and there's a line: a full point of drift at a fixed percentage, showing up in week three, on one movement, while the squat column held steady at 7.5 the whole time.

That's a movement-specific fatigue accumulation, and it was legible in week five. The deload was scheduled for week eight.

The stall showed up in the log three weeks before it showed up on the bar.

What changes if you can see the drift

Deload timing stops being a calendar decision. Most programs put the deload on a fixed week because a fixed week is the only thing a program can know in advance. Your log knows more than your program does, and a movement drifting a point over three weeks is a better argument for pulling the deload forward than the fact that it's week eight.

Max testing changes too. A working max that produces an 8.5 where it used to produce a 7.5 isn't a max anymore, it's an old measurement, and every percentage downstream of it is wrong in the same direction. Lifters usually discover this by missing a rep. The drift map says it earlier and more quietly.

And the per-movement resolution is the part that survives longest. Squats, deadlifts, and presses don't accumulate fatigue at the same rate for the same lifter, which every experienced lifter suspects and almost nobody can prove from their own log. Two fields per set, one training year, and it stops being a suspicion.

The log has to be built for it

None of this works if RPE lives in a session notes box. A rating attached to a whole workout can't tell you which movement drifted, and a rating you have to type into free text won't survive twelve weeks of Wednesdays. The field has to sit next to load and reps on every working set, and entering it has to cost about as much as entering the reps did.

The other requirement is boring and it's the one that actually bites. Drift is a trend, so the map needs a history longer than the block you're currently in. A lifter who's been training for six years and switching trackers every eighteen months has four fragments and no line. That's why Platepusher takes a CSV out of your previous tracker and lands every lift, every set, every date as native data rather than as an archive you can look at but not compute on. Your old logs are the experiment you already ran on yourself. They should be feeding the chart, not sitting in a folder.

Both fields, every set, one continuous history. The math runs while you're chalking up.

What we're watching next

The open question is how much of the drift map you can get without the lifter rating anything. Bar speed and heart rate recovery between sets are both cheap to capture on a watch and both track effort, and if either one predicts the RPE a lifter would have given, the rating becomes a check on the sensor instead of the only input. That's not settled, and the velocity literature is mostly built on the competition lifts rather than accessory work.

Until it is settled, the two-field log is the highest-signal thing a serious lifter can do that costs nothing.