Why the suggested load changes: fatigue, breaks and recalibration

The principle

Double progression tells you whether to go up, stay or drop one increment. But the right load also depends on context: you don't lift the same weight as your first exercise as you do after three others that have tired the same muscles, or after a month without training. Azetta estimates your current strength from your past sets and applies four corrections. For a regular lifter who follows the program in order, they are all equal to 1: they only kick in when something changes. The app always tells you why ("Why this weight?").

The Azetta method

Your estimated strength

From each set, the app estimates your maximum with the Epley formula, adding the reps you still had in reserve (2 if you didn't answer):

1. Position fatigue

Each hard exercise done before in the session costs 2.5% if it shares a primary muscle with the current exercise, 1.25% if it only works it as a secondary muscle, with a cap of 10%. An exercise planned later gets a lighter load; conversely, a set done while fatigued is credited as stronger (1RM ÷ (1 − fatigue)). An increase due only to position is capped at +10%.

2. The break

After 14 days without the exercise (or a variant of the same pattern), the app removes 1% per full week beyond that, without going below 85%:

3. Recalibration

The app compares what you were actually able to do (reps + reserve) with what was planned (top of the range + 2). The estimate moves towards each set faster the larger the gap (25% of the way, plus 10% per rep of difference). If the gap reaches 3 reps, the load is corrected in one go, from +10% at most to −15% at most, instead of moving one increment at a time. An increase is rounded down to the lower increment; a decrease never goes below 85% of the current load.

4. Transfer from a neighbouring exercise

For an exercise you have never done, a neighbour with the same pattern passes on its equipment-adjusted 1RM × 0.9; otherwise, the app compares your actual strength on the same muscle with the strength expected for your profile, and carries over half of the gap (ratio bounded between 0.5 and 2). The most cautious estimate wins.

The order of priority

1. A 1RM you entered for the exercise (valid until your next session of that exercise).
2. Undulating mode (pyramid or alternating ranges): last estimated 1RM, +2% if no set reached RPE 9.5.
3. Your history, with the corrections above.
4. Your declared maximums, then the transfer, then the profile-based estimate.

Why this choice

• Exercise order really changes performance: a muscle that has already been worked produces fewer reps at the same load.
• A short break (two weeks) costs almost no strength; beyond that, coming back a little lighter avoids failure and excessive soreness.
• Recalibration avoids weeks of climbing one increment at a time when the starting load was clearly too light, and protects you when it was too heavy.
• The transfer coefficients (0.9, half of the gap) are deliberately cautious.

Limits

• The percentages are Azetta's choices, reasonable but not taken from a specific study.
• The Epley estimate loses accuracy beyond about ten reps.
• Position fatigue only knows the order of the exercises, not how intensely you did them.

References

1. Epley B. Poundage Chart. Boyd Epley Workout. Lincoln (Nebraska): Body Enterprises, 1985.
2. Helms ER, Cronin J, Storey A, Zourdos MC. Application of the Repetitions in Reserve-Based Rating of Perceived Exertion Scale for Resistance Training. Strength and Conditioning Journal, 2016;38(4):42-49.
3. Simão R, de Salles BF, Figueiredo T, Dias I, Willardson JM. Exercise order in resistance training. Sports Medicine, 2012;42(3):251-265.