RPE and the rule of two: how hard is hard enough?

The program's instruction is that the last two reps of a working set should be genuinely difficult. It is deliberately plain language, and it is also the most misapplied line in the plan — mostly by people training much further from failure than they believe they are.

Here is the same instruction in the language coaches actually use, how to check whether you are hitting it, and what to do on the day your warm-up weight feels like a working set.

The two scales, which are the same scale

Rate of perceived exertion in lifting is anchored to how many reps you had left. RPE 10 means there was nothing left — the next rep would have failed. RPE 9 means one more was available. RPE 8 means two.

Reps in reserve states the same thing without the arithmetic: 2 RIR means two reps left in the tank. So the rule of two is RPE 8, or 2 RIR, and every set in the plan that says 'last two reps difficult' is asking for exactly that.

Note what the scale is not measuring. It is not how much the set hurt, how out of breath you were, or how much you disliked it. A set of twenty light squats can be deeply unpleasant and still be four reps from failure. Discomfort and proximity to failure are different readings, and only one of them sets the training stimulus.

Why a feel and not a percentage

Percentage-based programming requires a tested one-rep max, and testing one requires a maximal attempt — which is a poor idea for someone four days into a 30-day program with unfamiliar movements.

It also goes stale fast. Your true max drifts with sleep, stress and a falling calorie intake, so a percentage of a number you tested a fortnight ago is wrong in both directions on different days. Effort scales itself automatically. That is the whole reason the plan is written in it.

Worth noting that the interval days use a different ten-point scale. There, effort is about breathing and how hard you are working overall, not reps in reserve — a nine out of ten on a bike sprint has nothing to do with how many more you could do. Same numbers, different question.

What 2 RIR actually looks like

The honest test is not how the set felt, it is what it looked like. Effort is easy to misjudge; bar speed is not.

• Bar speed slows visibly on the second-to-last rep — this is the single most reliable cue you have, and it is why filming one set occasionally is worth the awkwardness
• Technique still looks like the technique you started with. If the last rep changed shape, you were closer to failure than you intended
• Two more reps would have been possible with real effort, not five more done comfortably
• On compound lifts you should need the rest period. If you are ready to go again after twenty seconds, the load was too light

The calibration problem

This is well documented and worth taking personally: people newer to lifting consistently overestimate how close to failure they are. Sets called 2 RIR often have four, five or six reps left in them, which is the difference between a training stimulus and a warm-up.

The fix is one honest reference point. Early in the program, take a single set on a safe movement to genuine failure — a machine, a dumbbell press, or anything where failing costs you nothing — and note what the last two reps felt and looked like. Calibrate everything against that memory. Do not do this on a barbell squat or an overhead press without safety pins or a spotter.

Accuracy also improves the closer you get to the end of a set, which is a useful quirk. Nobody can tell you reliably whether they have eight reps left, but most people can tell when they have two. That is precisely why the plan asks for a judgement at two rather than a judgement at five.

The day everything feels heavy

It will happen, usually in week three when the calorie target has dropped again. The instinct is to force last week's numbers. The better move is to keep the effort fixed and let the load come down: take ten percent off the bar, hit the same reps at the same RPE 8, and you have completed the prescribed session at the cost your body can actually pay today.

The opposite error is living at RPE 10. Training to failure on every set of every exercise costs far more recovery than it returns, particularly in a deficit — and it is the fastest route to a session you cannot finish on Thursday. Save true failure for the last set of an isolation movement, if you use it at all.

One boundary on all of this: effort is a judgement about muscular fatigue, not about pain. If a set is limited by something sharp in a joint rather than by the muscle running out, that is not an RPE 9 — stop the set and speak to a clinician.

“Keep the effort fixed and let the weight move. The effort is the training; the weight is only how you got there.”