Read the guide · Training
How Letz builds your workout plan
The Letz workout plan is generated by deterministic rules based on the ranges below. AI only selects preferences among exercises already vetted for safety, equipment, and available time; volume, rest, reps, and target effort come from the parameter sheet. Once generated, the plan receives an evidence adherence score, visible on the workout screen with a link to each study.
Numbers derived from this rule
| Parameter | Range | Weight | Rule |
|---|---|---|---|
| Reps per set | 6–12 reps2 variants by context | 60% | Broad ranges work when effort is high; 6 to 12 is practical for mass, 3 to 6 for maximal strength, and up to 20 with bodyweight.Load and rep range · Resistance Training, Strength, and Hypertrophy |
| Weekly sets per muscle group | 10–20 sets/week2 variants by context | 90% | Ten or more weekly sets per muscle produce greater hypertrophy; below four, the stimulus is insufficient; above twenty, returns diminish.Weekly Volume: Sets per Muscle Group · Minimum Effective Dose and Time-Efficient Training |
| Sets per exercise | 2–5 sets | 30% | Multiple sets per exercise outperform a single set; five per exercise is the practical ceiling per session.Weekly Volume: Sets per Muscle Group |
| Frequency per muscle group | 2–3 sessions/week | 80% | Each muscle group should be trained at least twice per week.Frequency: training each muscle at least twice per week |
| Resistance training sessions per week | 2–4 sessions/week | 70% | Two or more strengthening sessions per week; weekly consistency forms a habit in about six weeks.Physical Activity Guidelines for Adults · Frequency: training each muscle at least twice per week · Building a workout habit |
| Rest for compound exercises | 90–180 seconds | 60% | Compound exercises perform better with two minutes or more of rest; 90 seconds is the floor when time is limited.Rest Between Sets · Minimum Effective Dose and Time-Efficient Training |
| Rest for accessory exercises | 45–120 seconds | 30% | Isolation exercises tolerate shorter rest periods without losing quality.Rest Between Sets |
| Reps in reserve at the end of the set | 1–3 RIR1 variant by context | 70% | Ending sets with 1 to 3 reps in reserve already produces gains; absolute failure is not necessary and compromises recovery.Proximity to Muscular Failure · Load and Volume Autoregulation |
| Load increase when progressing | 2–10 % | 40% | When completing the rep range with proper technique, increase the load by 2 to 10% or add one rep per set.Progressive Overload and Periodization |
Rules and studies
- 01Resistance Training, Strength, and HypertrophyVarious training prescriptions improve strength and hypertrophy; heavier loads favor strength, and multiple sets favor hypertrophy.The generator prioritizes ensuring the user trains consistently and with good technique before fine-tuning details; the target range for sets and load is determined by their stated goal.
- 02Weekly Volume: Sets per Muscle GroupMore weekly sets per muscle produce greater hypertrophy, with diminishing returns; for strength, moderate volumes already capture most of the gains.The plan targets between 6 and 22 weekly sets per muscle group based on experience (6 to 12 for beginners, 10 to 20 for intermediates, 12 to 22 for advanced trainees), and the auditor treats a muscle group with zero sets as a structural gap, not a low score.
- 03Frequency: training each muscle at least twice per weekTraining a muscle group twice a week is superior to once for hypertrophy; for strength, higher frequency helps primarily because it distributes volume more effectively.With 2 or 3 days, the generator uses full-body training; with 4 or more, it splits upper/lower or push/pull/legs so each pattern appears at least twice.
- 04Load and rep rangeLight and heavy loads produce similar hypertrophy when sets are taken close to failure; heavy loads are superior for maximizing strength gains.Muscle gain and body recomposition goals use 6 to 12 reps; athletic performance uses 3 to 6; bodyweight-only workouts use 8 to 20 reps. The goal-specific rep range applies to the primary compound lifts — isolation and core work follow standard ranges, since maximal strength is not prescribed on abdominal exercises.
- 05Rest Between SetsRest intervals of two minutes or more favor strength and hypertrophy in compound exercises; short rest intervals work well when time is constrained.Compound lifts receive 120 seconds when the session is 60 minutes or longer and 90 seconds in shorter sessions; accessory movements get shorter rest.
- 06Proximity to Muscular FailureTraining to failure is not mandatory; sets finished with a few reps in reserve already produce gains, and hypertrophy improves as sets get closer to failure.The plan targets 1 to 3 reps in reserve (2 to 4 for beginners); the guided workout never requires failure and treats pain or breakdown in technique as a cue to stop.
- 07Progressive Overload and PeriodizationProgressing load or repetitions yields similar gains; varying the stimulus over weeks supports maximal strength more than keeping everything fixed.The default progression is double progression: first repetitions within the target range, then load or difficulty; logged workout history powers the recommendation for the next step.
- 08Minimum Effective Dose and Time-Efficient TrainingA few well-executed sets, two to three times a week, already yield meaningful gains; supersets and combined sets shorten the session without losing volume.Sessions of 15 to 30 minutes are never dismissed: the generator trims exercises and sets while preserving foundational movement patterns and the volume floor.
- 09Training response varies widely between individualsFollowing the same program, gains in strength and muscle mass range from negligible to substantial; study averages do not predict an individual's response.This is why Letz pairs general guidelines with individual data: parameters start within the literature-backed range and are adjusted based on logged history.