Every workout tracker tells you what you lifted. None of them tells you what shape your muscles are in right now.
MSCVL models muscle recovery using per-muscle decay rates — calves recover differently from biceps, and the app knows that. The fatigue heatmap shows you what's recovered, what's still fatigued, and what's starting to detrain.
Free. No subscription. No data collected or sold.

Core Feature Set
1. Workout Build & Gym Log

Create named workouts with ordered exercises.
Full active workout tracking: sets, reps, weight, time, distance
Per-exercise configurable metric types: weight/reps, time and reps, time and distance (cardio).
Custom notes at workout level and per-exercise level
Rest timer (auto-triggered on set completion, configurable per workout/exercise)
Navigation between exercises within a session
Previous performance data is shown during a session for comparison
Sound cues on set completion
2. Exercise Library

Large bundled default exercise database with primary/secondary muscle assignments, instructions, tips, video links, aliases, variation relationships, and tempo notation
10 exercise categories: Strength, Cardio, Stretching, Plyometrics, Strongman, Olympic Weightlifting, CrossFit, Calisthenics, Flexibility, Balance
Favorites system
Custom exercise creation with full muscle/equipment assignment
Filterable by muscle group, equipment, category, and search
3. My Gym — Equipment Inventory

Full equipment management across 9 equipment types: Dumbbells, Kettlebells, Medicine Balls, Resistance Bands, Plates, Barbells, Cable Machines, Plate-Loaded Machines, Cardio Equipment
Ownership tracking (owned vs. not owned)
"Use My Gym" mode filters all exercise lists & suggestions to owned equipment only
4. Muscle Fatigue Heatmap

Interactive SVG body model (front and rear) rendered as a color-coded fatigue heatmap
Each muscle has an individually configurable half-life (decay rate in hours)
Two layers: Fatigue level (how fatigued a muscle is right now) and Strength Loss level (are you deconditioned?)
Muscle-specific default half-lives are physiologically calibrated (e.g., calves 72h, hamstrings 64h, biceps 28h)
Automatically updated after every completed workout

5. Performance Records

Automatic 1-Rep Max (1RM) tracking per exercise
Quarter-mile time tracking
15-second rep count tracking
Per-exercise history with searchable records view
6. Analytics Dashboard (4 tabs)

Workout volume over time (total tonnage)
Exercise progression charts (weight, reps, estimated 1RM over time)
Session frequency and streak tracking
Date range filtering
7. Plate Calculator

Given a target load and a selected barbell, it calculates the exact plate configuration per side
Color-coded plate visual (IWF colors for metric, standard for imperial)
Works with your owned plates (My Gym integration) or generic mode
8. Muscle Fatigue Half-Life Customization

Users can dial in per-muscle recovery rates to match their personal physiology
Advanced enough that it has its own dedicated settings page
9. Profile & Settings

Name, weight, height, gender, age
Imperial/Metric toggle (affects all weight and height displays app-wide)
Dark mode
"Use My Gym" toggle
10. Data Backup and Transfer

Full export
Full import/restore (with confirmation warning)