RPE vs Heart Rate Training

Easy day: legs feel RPE 2, wrist HR sits at 158. Trust the feel and you gray-zone the week; trust glitchy optical data and you jog needlessly slow. Heart rate measures cardiac response. RPE measures perceived effort. The skill is knowing which signal wins when they conflict.

What Each Can Lie About

HR: lagging (especially wrist), altered by heat, caffeine, dehydration, stress, and cardiac drift. RPE: immediate, but skewed by mood, group pace, and fitness naivety. Calibrate both for a few weeks with the HR Zones Calculator and Zone 2 Calculator.

Worked Scenario: Mixed Signals on Tuesday

Plan: easy 50 minutes, Zone 2 ceiling 146 bpm. Athlete feels great (RPE 2) after coffee, wrist shows 152–158 on flats. Chest strap check: 154. Decision: slow until ≤146 even though it “feels easy” — heat plus residual fatigue, not a fitness breakthrough. Contrast: Wednesday intervals, 5×1000m. Mid-rep wrist HR spikes to 175 while pace/RPE match threshold targets from the Pace Calculator. Decision: trust pace/RPE for short reps; HR lags.

Session-Type Defaults

• Easy: both must pass — conversational and under Zone 2 ceiling
• Short hard: pace + RPE primary; HR confirms after warm-up
• Long tempo: once HR stabilizes, HR catches heat that pace ignores

Calibrate for Two Weeks

Log RPE (1–10) next to average HR on easy runs and one tempo. You want easy ≈ RPE 2–3 at Zone 2 HR, and tempo ≈ RPE 6–7 near LT HR. If RPE 3 always lands in Zone 3, your “easy” feel is biased high — trust the strap until perception recalibrates.

Decision Rule

If the session is easy and HR is high → slow down. If the session is easy, HR is low, but RPE feels hard → cut short or rest. If the session is hard and pace/RPE are on target while HR looks low → keep the workout (lag or strong day). If hard and HR skyrockets early in heat → extend warm-up or shorten the set.