Analytics Formulas

Forge uses scientifically-backed formulas to calculate your progress metrics. This page explains each formula in detail.

Overall Strength Coefficient

The Strength Coefficient is a comprehensive metric that tracks your overall strength development across all exercises.

Base Formula

Strength Coefficient = (Σ(max_weight / first_weight) / exercise_count) × 100

Where:

max_weight: The maximum weight lifted for each exercise across the lookback period
first_weight: The first recorded weight for that exercise
exercise_count: Total number of unique exercises performed

How It Works

The algorithm:

Filters workout history to the specified lookback period (default 90 days)
For each exercise, tracks:
- The first weight you ever used (baseline)
- The maximum weight you've lifted
- The date you achieved that max
Calculates the progress ratio for each exercise: current_max / first_weight
Averages all ratios and multiplies by 100

Interpretation

100: Baseline (no progress from starting weights)
150: You're 50% stronger overall than when you started
200: You've doubled your strength across all exercises

Progress Percentage

Progress % = ((current_coefficient - previous_coefficient) / previous_coefficient) × 100

Shows your improvement rate compared to the second-to-last data point.

Exercise-Specific Progress

Track detailed progress for individual exercises with three key metrics.

1. Maximum Weight Tracking

max_weight = max(set_1.weight, set_2.weight, ..., set_n.weight)

For each workout session, we record the heaviest weight lifted across all sets.

2. Volume Calculation

Volume = Σ(weight × actual_reps) for all sets

Total volume quantifies the total work performed. Higher volume typically indicates greater training stimulus.

3. Intensity Metric

Intensity (%) = (average_weight / max_weight) × 100

Where:

average_weight: Average weight across all sets in that session
max_weight: The heaviest weight lifted in that session

Intensity shows how close your working sets are to your maximum effort. Higher intensity (closer to 100%) indicates training closer to your max capacity.

Progress Percentage

Progress % = ((current_max - previous_max) / previous_max) × 100

Compares your latest max to your previous recorded max for this exercise.

Body Weight Tracking

Monitor your body composition changes over time.

Weight Change

Weight Change = current_weight - start_weight

Tracks absolute change from your first recorded weight in the lookback period.

Average Weight

Average Weight = Σ(weight_points) / total_points

Calculates your mean body weight across all recorded measurements.

Data Integration

Body weight data is sourced from:

Profile Service: Direct weight entries from "Body Weight" screen
Weight History: Historical weight logs stored with timestamps
Workout Sessions: Fallback to current weight if no history exists

Workout Volume Analysis

Volume is the total amount of weight lifted, a key indicator of training stimulus.

Daily Volume

Daily Volume = Σ(weight × reps) for all exercises in session

Aggregates the total volume for each workout day.

Weekly Volume

Weekly Volume = Σ(daily_volumes) for all days in week

Sums up all daily volumes for each training week. Week starts on Monday.

Average Volume

Average Volume = Σ(weekly_volumes) / total_weeks

Your typical weekly training volume across the entire lookback period.

Week Definition

Weeks are calculated as Monday to Sunday periods using this helper function:

week_start = date - Duration(days: date.weekday - 1)

Workout Frequency

Track how often you train and maintain consistency streaks.

Weekly Frequency

Weekly Frequency = workouts_per_week

Counts the number of workout sessions completed each week.

Average Frequency

Average Frequency = Σ(weekly_frequencies) / total_weeks

Your typical weekly training frequency.

Streak Calculation

Streak += 1 if (previous_date - current_date) ≤ 2 days

Counts consecutive training days with a 2-day grace period to account for rest days.

Streak Logic

The streak algorithm:

Sorts all workout dates in descending order (most recent first)
Starts from the most recent workout
Continues the streak if workouts are within 2 days of each other
Breaks the streak if the gap exceeds 2 days

Consistency & Completion Rate

Measures how well you stick to your planned workouts.

Session Completion Rate

Session Completion % = (sets_completed / sets_planned) × 100

Calculates what percentage of planned sets you actually completed in each session.

Overall Completion Rate

Overall Completion % = (total_sets_completed / total_sets_planned) × 100

Your aggregated completion rate across all workouts in the lookback period.

What Counts

Sets Planned: The target number of sets specified in your workout program
Sets Completed: The actual number of sets you logged

Interpretation

>90%: Excellent adherence to your program
75-90%: Good consistency with occasional incomplete workouts
<75%: May need to adjust program difficulty or time management

Muscle Recovery & Training Readiness

Forge tracks when each muscle group was last trained and calculates recovery priorities to recommend the best muscles to train next.

Days Since Last Training

days_since[group] = (now - last_training_date[group]).inDays

For each muscle group, the system scans all workout history (including old exercises matched to current muscle group assignments) and finds the most recent date that muscle was trained.
Default value: 14 days if a muscle group has never been trained.

Recovery Priority

if days < optimal: priority = (days / optimal) × 0.3
if days == optimal: priority = 0.7
if days < optimal × 2: priority = 0.7 + ((days - optimal) / optimal) × 0.3
if days ≥ optimal × 2: priority = 1.0 + ((days - optimal × 2) / 7).clamp(0, 0.5)

Where:

days: Days since last training for this muscle group
optimal: Optimal recovery days for this muscle group (see table below)

Priority < 0.3 = needs rest, 0.3–0.7 = recovering, ≥ 0.7 = ready to train.

Optimal Recovery Days per Muscle Group

Muscle Group	Recovery Days
Legs	3 days
Back	3 days
Glutes	3 days
Chest	2 days
Shoulders	2 days
Biceps	2 days
Triceps	2 days
Calves	2 days
Forearms	1 day
Wrists	1 day
Core	1 day
Cardio	1 day

Workout Priority Score

Workout Priority = Σ(recovery_priority[group] × muscle_score) / Σ(muscle_score)

Where muscle_score depends on intensity:

Primary: score = 3
Secondary: score = 2
Stabilizer: score = 1

This weighted average prioritizes workouts that target muscles most in need of training, while accounting for which muscles are primary vs secondary in each exercise.

Cross-referencing Old History

When exercises in old workout history don't have muscle group assignments (because they were added before the muscle group feature), the system automatically matches them by exercise ID to the current exercise definitions. This ensures that all historical data is used when calculating days since last training, not just recent workouts.

Exercise Completion & Regression Tracking

Forge visually indicates exercise completion status and performance regression to help you stay on track.

Completion Status (Program View)

is_completed = exercise.id ∈ {last_session.exerciseResults[].exercise.id}

When viewing a program's exercise list, each exercise is checked against the most recent completed session of that workout. Exercises that were not completed last time are highlighted in red with a × icon, so you know what you skipped and need to focus on next time.

Rep Regression Detection (Calendar View)

is_regression = (current_total_reps < previous_total_reps)
where total_reps = Σ(set.actualReps) for all sets of an exercise

When viewing workout history through the calendar, each exercise's total reps are compared against the previous session of the same workout. If you performed fewer total reps than last time, the exercise is highlighted in yellow/orange with a trending-down indicator showing the comparison (e.g., "18 / 24 reps").

Lookback Period

All formulas use a configurable lookback period to filter relevant data.

Date Filtering

cutoff_date = current_date - Duration(days: lookback_days)

Only workouts after this cutoff date are included in calculations.

Available Periods

30 days: Recent short-term progress
90 days (default): Medium-term training cycles
180 days: Long-term trends and patterns
365 days: Annual progress and year-over-year comparison

Example Calculation

Let's walk through a real example of calculating the Strength Coefficient.

Scenario

A user has tracked 3 exercises over 90 days:

Exercise	First Weight	Max Weight	Progress Ratio
Bench Press	60 kg	90 kg	1.50
Squat	80 kg	120 kg	1.50
Deadlift	100 kg	140 kg	1.40

Calculation

Total Progress Ratio = 1.50 + 1.50 + 1.40 = 4.40
Exercise Count = 3
Strength Coefficient = (4.40 / 3) × 100 = 146.67

Result

This user has improved their overall strength by 46.67% across all exercises!