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Polarized 80/20 training: what the easy/hard split means for functional fitness

Elite endurance athletes spend about 80% of their sessions easy (below the first lactate threshold, LT1) and about 20% hard (above the second threshold, LT2). The failure mode that model warns about is real: letting sessions that should be easy drift up into the moderate middle, accumulating fatigue without proportional adaptation. For a CrossFit athlete the target is pyramidal-tolerant, not strictly polarized — the sport itself is threshold-heavy, so programmed metcon time in the middle-to-hard zones is intended work. Protect the easy base; do not try to delete the middle.

~80%

sessions easy (below LT1)

~20%

sessions hard (above LT2)

What the research says

Stephen Seiler's analysis of how elite endurance athletes actually train found a consistent polarized distribution: the large majority of training volume sits at low intensity, a meaningful minority sits at high intensity, and surprisingly little lands in the moderate "threshold" zone. Athletes who instead concentrate work in that middle zone tend to plateau — the intensity is high enough to fatigue but not high enough to drive the top-end adaptations, and not easy enough to build a durable aerobic base.

For a hybrid or CrossFit athlete, the practical translation is not to copy the endurance-athlete distribution wholesale — functional fitness is a threshold-heavy sport, so a pyramidal-tolerant distribution fits it better (Stöggl & Sperlich 2015; Filipas 2022). Protect genuine Zone-2 volume for the aerobic base that clears lactate and fuels recovery, make the hard sessions genuinely hard, and keep easy days genuinely easy rather than letting them drift up. The moderate-zone time your programmed mixed-modal metcons produce is intended hard conditioning — it is the sport, not junk to eliminate.

How Dawg & Rabbit Fitness applies it

The program prescribes 2–3 true Zone-2 sessions per week against your individualized heart-rate zones (computed from your resting and max HR, %HRR/Karvonen), protects that easy aerobic base, and keeps your hard conditioning hard on purpose — it does not chase a zero-middle split by cutting programmed metcon volume. Your conditioning distribution is visible alongside the citation.

Sources.
Seiler (2010). What is best practice for training intensity and duration distribution in endurance athletes? International Journal of Sports Physiology and Performance, 5(3), 276–291. doi:10.1123/ijspp.5.3.276
Seiler & Kjerland (2006). Quantifying training intensity distribution in elite endurance athletes. Scandinavian Journal of Medicine & Science in Sports, 16(1), 49–56. doi:10.1111/j.1600-0838.2004.00418.x

Last updated: 21 July 2026

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