Two Pacing Modes
During onboarding, you choose how you want to receive pacing guidance:
- RPE (Effort-Based): descriptive effort levels from conversational easy to all-out sprint, using a 1 to 10 scale based on the Borg Rating of Perceived Exertion.
- VDOT (Pace-Based): specific pace ranges per mile or kilometer (matching your plan's units) calculated from your fitness level using the Jack Daniels Running Formula.
VDOT Pace Zones
Pheidi supports VDOT values from 20 to 85 and calculates five training zones for each:
| Zone | Purpose |
|---|---|
| Easy | Aerobic base building, recovery |
| Marathon | Race-specific endurance pace |
| Tempo | Lactate threshold work |
| Interval | VO2max development |
| Repetition | Speed and running economy |
Your paces are calculated from Daniels' formulas directly, not read off a table of sample values. Every VDOT gets its own paces: VDOT 42 and VDOT 43 are prescribed different numbers, and your paces shift smoothly as your fitness changes rather than jumping when you cross a threshold. These are the same formulas behind the VDOT calculator, so a pace you look up there is the pace the app prescribes.
VDOT Estimation
If you have a recent race result, Pheidi can estimate your VDOT from your finish time across 5K, 10K, Half Marathon, and Marathon distances. You can also set your VDOT manually in Settings.
Pace zones live inside the Pheidi app, sign in to see yours.
Research & evidence
Science behind this feature from pheidi.training.
- Running Training Plan: The Complete Guide Pillar hub linking 48+ deeper dives, start here for the full picture.
- VDOT Race Prediction How Jack Daniels' effective VO2max turns one race into a full pace table.
- Polarized Training: The Gray Zone Problem Why most runners train too hard on easy days and too easy on hard days.
- The 80/20 Polarized Training Rule Dr. Stephen Seiler's session-count distribution across elite endurance sports.
- The Gray Zone Training Mistake Zone 2 costs fatigue without the adaptations of Zone 3.
- Individualized Training Zones (2025) Why fixed heart rate zones fail and what replaces them.
- 2024 Training Intensity Meta-Analysis Polarized beats threshold-heavy at equal total volume.
- Measuring 80/20 Training Session count vs time-in-zone and why the metric changes the answer.
See also
- How Load Distribution Works How Pheidi shapes weekly distance around your long run using a shape-based system that keeps the hierarchy of run lengths consistent across the week.
- How Workout Logging Works How Pheidi tracks your completed workouts: quick-complete, manual entry, post-workout feedback, and how logged data adapts future training.
- How Garmin Watch Export Works Send structured workouts to your Garmin watch with pace targets and interval cues. Export FIT files from any Pheidi workout.