Your strength score, from 0 to 1000

The principle

To know whether you are getting stronger, you need a number that depends neither on the day's exercises nor on your build. Azetta compares each of your best sets with what an intermediate lifter of your sex and body weight lifts on the same exercise, then turns the gap into points: 400 points is the intermediate standard, 1000 the ceiling. The score is computed per muscle, then for the whole body.

The Azetta method

1. Only free weights count

An exercise counts if it is done with a barbell, dumbbells or an EZ bar, as a strength exercise, and if the app knows its standard. Everything else is shown as "not counted", never guessed:

• machines and cables: the load shown depends on the pulleys and levers, it does not compare from one machine to another;
• body weight, bands, kettlebells: no shared load standard;
• variants without a reliable standard: Olympic lifts (clean, snatch, jerk and their pulls), bands and chains, partial movements (rack pull, board press, pin press), speed or jumping work, one-leg work, reverse-grip and Zottman curls, rear-delt work, pullovers, upright rows, Zercher, hack squat, core exercises.

2. The estimated max

Each finished working set of 1 to 12 reps with a load gives an estimated one-rep max (Epley formula). Warm-up sets do not count; beyond 12 reps, the estimate becomes too imprecise.

For each session, only the best set of the exercise is kept.

3. The intermediate standard, on the day of the session

• The body weight is that of your weigh-in nearest the day of the set (otherwise your profile's), scaled to the power 2/3: strength does not grow as fast as body weight.
• The ratio is the max of an intermediate man of 75 kg as a multiple of his body weight:

• The sex share: 1.0 for a man; 0.8 for the lower body and 0.6 for the upper body for a woman; 0.9 and 0.8 if your sex is not specified.
• With dumbbells, the standard is that of one dumbbell, as a share of the barbell standard of the same movement, read on the StrengthLevel tables for an 80 kg man:

4. Points from 0 to 1000

The ratio of your estimated max to the standard becomes points, along straight lines between anchors set on the columns of the same strength tables:

where (R₁, P₁) and (R₂, P₂) are the two anchors around your ratio.

5. Three months, then the muscle, then the total

• Each exercise keeps its best points of the last 90 days. A set expires 90 days after it was done; the next best of the window takes its place.
• An exercise belongs to the group of its main muscle (chest, back, shoulders, quadriceps, hamstrings, glutes, biceps, triceps, traps, calves).
• A muscle's score is the mean of its exercises; your overall score, the mean of the muscles that have one. Rounding happens at the end.

6. The seven levels

The levels are narrower at the top: each step there takes more real strength.

7. The history

The app recomputes the score at the end of each week (on Sunday) since your first counted set, then today, each time from the sets valid that day. It shows the change over 7 days for the overall score and over 30 days for each muscle; the next level appears on the chart when it is less than 60 points away.

Why this choice

• Comparing with a standard per exercise lets barbell and dumbbells, lower and upper body mix: each set is judged against what is expected on that very movement.
• The anchors on the columns of the tables give the points a meaning: 400 is the published intermediate level, 575 the advanced, 825 the elite. Between them, a straight line: no jump, no hidden step.
• A scale from 0 to 1000 shows progress from one week to the next, where a short scale would round it to zero.
• Scaling to the power 2/3 corrects the fact that a person twice as heavy is not twice as strong.
• The 90 days keep the score current: an old performance eventually drops out, a break shows.
• The standards are rounded down a little: the score reads generous rather than harsh.

Limits

• The standards describe a population; your build, your technique and your age (not taken into account) can set you apart from them.
• The Epley estimate loses precision towards 10 to 12 reps and varies from one exercise to another.
• A muscle with a single counted exercise depends on that exercise alone.
• Machines, body weight and kettlebells do not count, even if you train with them a lot.

References

1. Epley B. Poundage Chart. Boyd Epley Workout. Lincoln (Nebraska): Body Enterprises, 1985.
2. StrengthLevel.com, strength standards per exercise (beginner, intermediate, advanced, elite columns).
3. Kilgore L, Rippetoe M, Pendlay G. Strength Standards, tables published on ExRx.net.
4. Symmetric Strength, strength standards per movement (symmetricstrength.com).
5. Jaric S. Muscle strength testing: use of normalization for body size. Sports Medicine. 2002;32(10):615-631.