Easy minutes count. “Optimal for everyone” goes further than the data do.
The claim
Zone 2 is the optimal intensity for everyone.
What the evidence says
The idea that easy exercise below the lactate threshold is the optimal intensity comes largely from observations of elite endurance athletes (about 80% easy, 20% hard, 10 to 13 sessions a week). A 2025 narrative review argues the evidence does not support Zone 2 as the optimal intensity for the general public and that higher intensities matter more at lower training volumes. A meta-analysis of 17 studies (437 athletes) found a small edge for polarized training (mostly easy, some hard) on VO2peak (11 of the 17 studies, 284 athletes; SMD 0.24, 95% CI 0.01–0.48) and no clear difference in time-trial performance.
The numbers
- Seiler 2010: descriptive studies of elite endurance athletes (10–13 sessions a week): about 80% easy, 20% hard.
- Storoschuk 2025 (narrative review): current evidence does not support Zone 2 as the optimal intensity for mitochondrial or fat-oxidative capacity; higher intensities are critical for cardiometabolic health, particularly at lower volumes.
- Silva Oliveira 2024: 17 studies, 437 athletes; polarized vs other distributions: VO2peak (11 studies, 284 athletes) SMD 0.24 (0.01–0.48), only in <12-week interventions and highly trained athletes; time trial SMD −0.01, threshold power SMD 0.04 (no difference).
- We found no trial testing Zone 2 against deaths or disease.
Verdict: Not proven
Easy minutes count. “Optimal for everyone” goes further than the data do.
Why only this far: Athlete data, mechanisms and one narrative review. We found no trial testing Zone 2 against deaths or disease in everyday people.
Evidence level C: Small or mechanistic studies, expert consensus. How verdicts work.
What we don’t know
We found no trial testing Zone 2 against deaths or disease in everyday people. Most of the data come from trained athletes.
Sources
Checked 15 Oct 2026. Every link opens the original paper or its PubMed record.
- Storoschuk et al., Sports Med 2025Narrative review (position article)DOI 10.1007/s40279-025-02261-y · PubMed 40560504
- Silva Oliveira et al., Sports Med 2024Meta-analysis (17 studies, 437 athletes)DOI 10.1007/s40279-024-02034-z · PubMed 38717713
- Seiler, Int J Sports Physiol Perform 2010Review (descriptive studies of elite endurance athletes)DOI 10.1123/ijspp.5.3.276 · PubMed 20861519
Disclosure: one author of the narrative review is an adviser to and holds equity in Longevity League, a company whose services partly relate to exercise.
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Educational content, not medical advice. This check rates a claim, not you or your health. Talk to a doctor about your own situation. Found a mistake? Write to hello@mostlyproven.com.
