How the fitn3s Workout Algorithm Works
Every day, fitn3s generates a workout from scratch. Not a template — a personalised plan built from what we know about you, your history, and training science. Here's exactly what goes into it.
The inputs
Four things feed into every plan the algorithm generates.
Your goals
You tell fitn3s whether you're here to build muscle, lose weight, stay active, or improve flexibility. Each goal influences which exercise types score higher: strength work for muscle, cardio for weight loss, flexibility for mobility. Multi-goal? The algorithm uses union scoring — an exercise that satisfies any one of your goals gets a boost.
Your fitness level
A quick 5-minute test — maximum push-ups in 60 seconds and a wall-sit hold — sorts you into a starting tier that seeds your targets on the 40-level progression scale. This prevents beginners from getting hard exercises before they're ready, and ensures experienced users aren't stuck with easy ones. The test is optional.
Your body part preferences
Tell fitn3s which areas you want to focus on — chest, legs, core, glutes, arms, shoulders, back, or full body — and the eligible exercise pool narrows accordingly. Leave it open and everything is fair game.
Your recent workout history
The last two sessions' exercises are hard-excluded — you won't see them again so soon. Exercises from days 3–7 are soft-penalised (scored −2), so they're unlikely but possible. This enforces variety and prevents the same muscles getting hammered every day without recovery.
Today's Plan
4 exercises · ~15 min
Goal: build muscle
Level: The Regular
Push-Ups
12 reps
Glute Bridges
15 reps
Mountain Climbers
30 s
Bird Dog
10 per side
No repeated exercises from yesterday
How exercises are selected
Once the pool of eligible exercises is established, the algorithm scores and selects them in two passes.
Scoring:Each exercise gets a score based on how well it matches your goals. A strength exercise scores +2 for a muscle-building goal. A cardio exercise scores +2 for weight loss. Exercises from recent sessions are penalised −2. The algorithm doesn't pick randomly — it picks what makes sense for you today.
Variety pass:The algorithm first picks the top-scoring exercise from each body part group. This ensures you don't end up with four chest exercises in one session.
Fill pass: Remaining time in your chosen session length (10, 15, or 20 minutes) is filled with the highest-scoring remaining exercises. Each exercise costs its duration plus 30 seconds of rest.
Shuffle:The final list is shuffled so you're not always starting with the same body part.
How it gets harder over time
The algorithm isn't just about today's plan. It tracks your progress on every exercise individually.
Personal targets, not generic ones
Every exercise has a personalised rep or duration target set at your level. Complete a push-up set at your target, log it, and the app records it. Hit your target 3 sessions in a row and the target steps up automatically — one rep, a few seconds. Miss it? The target holds steady — it steps up but never drops.
Calibrated from your fitness test
If you've taken the fitness test, your starting targets are set relative to your assessed level, not at the generic beginner level. A level 2 athlete starts closer to their actual ability from day one.
Your Push-Up Progress
Target raised automatically 3×
What the algorithm doesn't do
- ❌ It doesn't require you to log your food, sleep, or heart rate.
- ❌ It doesn't ask you to rate your fatigue before every session.
- ❌ It doesn't have 47 settings to configure.
- ✅ It does generate a good, personalized workout every day — automatically.
See it in action for yourself. The first plan takes about 30 seconds to set up.
Build my first plan →No equipment. No gym. Free to start.