The first load suggested for an exercise you have never done

The principle

The very first time you do an exercise, the app has no data on you for that movement. Rather than leaving you to guess, it estimates your one-rep maximum (1RM) from public strength standards, then derives a cautious working load from it. From your first logged session, this estimate is replaced by your actual performance.

The Azetta method

1. A reference strength ratio

For each exercise, a ratio expresses the barbell 1RM of an intermediate 75 kg man, as a multiple of his body weight. A few values: deadlift 1.5; squat and leg press 1.25; bench press 1.0; incline bench press 0.85; military press 0.65; pulldowns and rows 0.9; lunges 0.7. Isolation exercises have their own ratios depending on the muscle (for example 0.5 for biceps, 0.45 for triceps, 0.3 for shoulders).

2. Your weight, scaled

Strength doesn't grow in proportion to body weight: it follows muscle cross-sectional area more closely. The app therefore uses allometric scaling to the power of 2/3:

3. Your experience

Between these points, the value is interpolated, then bounded by your declared level (beginner 0.5-0.85; intermediate 0.75-1.25; advanced 1.0-1.4).

4. Sex and equipment

• Sex: man 1.0; woman 0.8 for the lower body and 0.6 for the upper body; not specified 0.9 and 0.8.
• Equipment: machine × 1.3; dumbbell or kettlebell × 0.4 (per hand); cable isolation × 0.7 on top.

5. From your 1RM to your working load

The app aims for the top of your rep range while leaving you 2 reps in reserve, with the Epley formula:

The load is rounded down to the increment of your equipment (2.5 kg on the barbell, 2 kg on dumbbells, 4 kg on the kettlebell, 5 kg on machines); on the barbell, it never goes below the empty 20 kg bar. If you have entered your gym's plates, it is then brought to the nearest load your bar and plates allow. Outside a gym, it never goes above your heaviest dumbbells.

An exercise placed after other hard exercises for the same muscle gets a little less: this is session fatigue, described in the article on adaptive load.

If you already know a similar exercise

Before using the standards, the app looks at your neighbouring exercises. An exercise with the same pattern (same primary muscle, same type of force and movement) passes on its equipment-adjusted 1RM multiplied by 0.9. For example, a 100 kg bench press gives 100 × 0.4 × 0.9 = 36 kg per hand on the dumbbell bench press, i.e. 26 kg for 8 reps. If you have declared your maximums on the squat, bench press or deadlift, they also take precedence over the standards.

Why this choice

• Public strength standards (StrengthLevel.com, cross-checked with the Kilgore, Rippetoe and Pendlay tables) give a known order of magnitude for each level; the ratios used are even rounded down slightly.
• Scaling to the power of 2/3 corrects the fact that a person twice as heavy is not twice as strong.
• Aiming for 2 reps in reserve and rounding down makes the first session deliberately comfortable: it is better to raise the load afterwards than to fail on day one.

Limits

• This is only a population estimate: your actual strength may differ from it clearly, especially on technical exercises.
• Age is not taken into account in this estimate.
• The Epley formula is less accurate beyond about ten reps.

References

1. Epley B. Poundage Chart. Boyd Epley Workout. Lincoln (Nebraska): Body Enterprises, 1985.
2. StrengthLevel.com, strength standards by exercise ("intermediate" column).
3. Kilgore L, Rippetoe M, Pendlay G. Strength Standards, tables published on ExRx.net.