Heart Rate-Based Training

Where we are, where we're going, and how heart rate zones will integrate into your training plan.

Where We Are Today

Pheidi currently supports two ways to guide your workout intensity:

Both work well, but many runners — especially those with GPS watches — think in heart rate. Heart rate zones are a natural third option that bridges the gap between objective pace data and subjective effort feel.

The Polarized Training Foundation

Pheidi's plan engine already enforces a polarized training distribution based on Dr. Stephen Seiler's research and multiple meta-analyses. The principle: approximately 80% of your training volume should be easy, with only 20% at hard intensity. Minimal time should be spent in the "gray zone" — too hard for recovery, too easy for speed gains.

3-Zone Polarized Model
Zone HR (% of Max) RPE Target Volume Feel
Zone 1 — Easy 0–75% 1–4 75–90% Conversational, relaxed breathing
Zone 2 — Gray 76–85% 5–6 0–10% Moderate — minimize this!
Zone 3 — Hard 86–100% 7–10 10–25% Tempo to all-out effort

This maps cleanly to 5-zone models on watches: Garmin/Apple zones 1–2 = Easy, zone 3 = Gray (minimize), zones 4–5 = Hard.

Today the plan engine uses this model to structure your week — placing the right mix of easy runs, quality sessions, and rest days. Heart rate zones will make this visible on each workout.

Intensity Targets by Training Phase

The optimal intensity distribution shifts as you progress through your plan. Early phases are more aerobic; later phases allow more hard work as your fitness builds.

Phase Easy (Zone 1) Gray (Zone 2) Hard (Zone 3)
Base 85–95% 0–5% 5–15%
Build 75–85% 0–5% 15–25%
Peak 70–80% 0–5% 20–30%
Taper 80–90% 0–5% 10–20%

Notice the gray zone stays at 0–5% across all phases. That's intentional. The most common training mistake is spending too much time at moderate intensity.

Roadmap

Phase 1 — HR Zone Display

Add heart rate zones as a third pacing option alongside VDOT and RPE. Each workout card will show a target heart rate range based on your max HR.

What this looks like
  • New profile option: enter your max heart rate (manual or age-estimated)
  • Each workout shows its HR target — e.g., "Easy run: keep HR below 150 bpm"
  • VDOT, RPE, and HR can complement each other — see pace, effort, and heart rate together
  • Workout type maps to HR zone: easy/long/recovery runs → Zone 1, tempo → upper Zone 2/lower Zone 3, intervals → Zone 3

Phase 2 — HR Tracking & Gray Zone Alerts

After workouts, log your actual average heart rate. Pheidi will analyze your intensity distribution across the week and flag gray zone creep — the most common training mistake for recreational runners.

What this looks like
  • Post-workout: optional field for average HR and max HR
  • Weekly intensity distribution chart — see how much time you spent in each zone
  • Gray zone alerts: "Your Tuesday easy run averaged 82% max HR — that's gray zone. Try slowing down to keep it under 75%."
  • Trend tracking over weeks — are you getting more polarized or drifting toward the middle?

Phase 3 — Wearable Integration & Adaptive Readiness

Connect your watch or wearable to bring in HRV, resting heart rate, and sleep data automatically. Pheidi combines this with your subjective feel to assess daily readiness and adjust your training accordingly.

Supported platforms (planned)
Platform Data
Garmin Body Battery, HRV Status, Sleep Score, Resting HR
Apple Watch HRV (rMSSD via HealthKit), Resting HR, Sleep Duration
Whoop Recovery Score, HRV, Sleep Performance
Oura Readiness Score, HRV, Sleep Score, Resting HR
Polar Nightly Recharge, HRV, Sleep Score

Composite readiness score

Your daily readiness is a weighted blend of subjective feel and wearable data:

Signal Weight
Your subjective rating (how you feel) 40%
HRV trend 25%
Sleep quality 20%
Resting HR trend 15%

Override rule: If you feel tired or exhausted (subjective ≤ 2), Pheidi always downgrades regardless of wearable data. Your feel matters more than numbers.

How readiness adjusts your plan
Readiness Score Adjustment
Below 40 Suggest rest day or easy walk
40–60 Downgrade hard sessions to moderate
60–80 Proceed as planned
Above 80 Optional stretch goal offered (never pushed)

Design Principles for HR Features

Heart rate data is powerful but easy to misuse. These principles guide how Pheidi will integrate it:

  1. Subjective feel always wins. Wearable data supplements your judgment — it never overrides it. If you feel terrible but your HRV looks great, we trust you.
  2. Trends over snapshots. A single bad HRV reading means nothing. Pheidi shows trend arrows (↑ ↓ →) rather than raw numbers to avoid data anxiety.
  3. Learning period before auto-adjustments. Wearable data needs 7–14 days of baseline before it's useful. During this period, Pheidi shows data but doesn't act on it.
  4. Simple zones, not data overload. Three zones (easy, gray, hard) are enough. We won't drown you in five-zone breakdowns and VO2max estimates.
  5. Always optional. HR features enhance the experience — they're never required. VDOT and RPE remain first-class pacing options.

Key Takeaway

Heart rate training in Pheidi follows the same philosophy as everything else: clarity over complexity. Three zones. Polarized distribution. Your feel matters most. We'll add HR data gradually — starting with simple zone targets on each workout, then post-run analysis, then wearable integration — so you're never overwhelmed.

Research & evidence

Science behind this feature from pheidi.training.

See also