Heart rate vs power zones: which should you use for training?

Power and heart rate both tell you how hard you are working, but they do not tell you the same thing at the same speed. Here is when to trust each one — and how to set the zones up so they actually line up.

The 30-second rule

Power responds in about a second. Heart rate responds in 30 to 90 seconds, and keeps rising after you stop pushing (cardiac drift). For short, sharp efforts — a 30-second sprint, a 1-minute VO2 rep — power is the truth. For sustained aerobic work, heart rate catches up and (mostly) agrees.

When power is the right signal

• Short intervals (VO2max, anaerobic, sprints)
• Criteriums and races with surges
• Indoor trainer sessions (no drift, no heat artefacts)
• Setting Intensity Factor (IF) and TSS

When heart rate is the right signal

• Long endurance rides, especially in heat (cardiac drift is real)
• Running and other sports without a power meter
• Recovery days (low HR = true recovery, even if power is spiky)
• Days when you suspect the power meter is miscalibrated

How to set the zones so they match

The classic 7-zone model (Coggan) lines up like this on a fit cyclist:

• Z1 / Active recovery — <55% FTP, <68% LTHR
• Z2 / Endurance — 56–75% FTP, 69–83% LTHR
• Z3 / Tempo — 76–90% FTP, 84–94% LTHR
• Z4 / Threshold — 91–105% FTP, 95–105% LTHR
• Z5 / VO2max — 106–120% FTP, >106% LTHR
• Z6 / Anaerobic — 121–150% FTP
• Z7 / Neuromuscular — maximal sprints

The percentages are approximate — your exact zones depend on your individual physiology, the sport and the day. The point is that power and HR should put you in roughly the same zone at the same effort, most of the time. Read more in our Zone 2 guide.

The drift problem

On a 3-hour ride in summer, your heart rate can drift up 10–15 bpm at the same power output. The work has not gotten easier — your body is just warmer, more dehydrated, more fatigued. Trust HR for how hard you are working, trust power for how much work you did. They answer different questions.

Practical rules for endurance training

• Build your zones from a test, not a guess. For power: a 20-minute test gives you FTP (how to). For HR: a 30-minute all-out gives you LTHR.
• Re-test every 4–6 weeks. Form improves, zones shift.
• Pick one primary signal. Decide per workout which number you will follow — usually power indoors, HR outdoors in heat.
• Use both in the dashboard. TrainCurve shows the live zone (power or HR) plus your Fitness, Fatigue and Form trend. Start free.