Polarized training in practice
Endurance athletes across sports converge on roughly 80% of sessions easy (Zone 1–2) and 20% hard (Zone 4–5). The middle zone feels productive but accumulates fatigue without the adaptations of either end.
- • If you cannot hold a conversation, you have left Zone 2.
- • Heat, caffeine, dehydration, and stress all shift heart rate up 5–10 bpm.
- • Wrist optical sensors lag during intervals — use a chest strap for hard sessions.
FAQ
What is my target heart rate for fat burning?
The 'fat burning zone' around 60–70% of heart rate reserve does use a higher share of fat for fuel, but total calories burned matters more for fat loss. Train in Zone 2 for endurance, not because of the fuel mix.
Is 220 minus age accurate?
It is a rough population average with ±10–12 bpm error. The Tanaka equation used here is more accurate, especially for adults over 40.
What should my resting heart rate be?
Most adults sit between 60 and 100 bpm; trained endurance athletes often fall between 40 and 55. Consistent upward drift is worth mentioning to a clinician.
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