The two most-confused intensities in distance running are Zone 2 and tempo. They feel different, they train different systems, and most amateurs accidentally turn the first into the second.
Side by side
| Zone 2 | Tempo (Z3-Z4) | |
|---|---|---|
| %Max HR | 60–70% | 78–88% |
| RPE | 3–4 | 6–7 |
| Breathing | Through the nose comfortably | Heavy, controlled |
| Speaking | Full sentences | Short phrases |
| Trains | Mitochondria, fat oxidation, capillaries | Lactate clearance, threshold |
| Duration | 30 min – 3 hr | 20–60 min |
| Recovery cost | Low — daily OK | High — once or twice a week |
Why this confusion is expensive
Running your easy days at tempo turns 80 percent of your week into low-grade hard work. The aerobic adaptation drops and your scheduled hard sessions arrive on tired legs. Most plateaus look exactly like this.
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