Polarized 80/20 Training Calculator: Weekly Easy, Threshold and Hard Time
Split weekly running, cycling or rowing volume with the 80/20 polarized model: easy, threshold and high-intensity minutes, a three-zone split with the Polarization Index, a session-by-session weekly plan with warm-ups and cool-downs, and heart-rate limits from your lactate threshold.
How it works
Easy time = weekly volume × easy% · Hard time = volume − easy time · Threshold time = volume × threshold% · High-intensity time = hard − threshold · Polarization Index = log10(Z1 ÷ Z2 × Z3 × 100), zones as fractions; above 2.00 = polarized
The polarized, or 80/20, model puts about four-fifths of training time at a genuinely easy intensity, below the first ventilatory or lactate threshold, and reserves the remaining fifth for hard work, with little time in the moderate "grey zone" between the two thresholds. Reviews of elite endurance athletes find 75–80% low, about 5% threshold and 15–20% high-intensity work in polarized blocks, while pyramidal plans swap some high-intensity time for threshold work. The calculator turns your weekly hours into minutes for each of the three zones, works out the Polarization Index of Treff and colleagues (above 2.00 counts as polarized) and lays out a week: about one session in five is hard, each with a warm-up and cool-down that count as easy time, and the remaining easy minutes are spread across the easy sessions. Time-in-zone and session counting give different numbers: a week of four easy runs and one interval session can be 80/20 by sessions yet nearer 90/10 by time, because the warm-up and recoveries are easy. Enter your lactate threshold heart rate to get the heart-rate limits used by the 80/20 Endurance zone system: low intensity below about 90% of LTHR, moderate 90–100%, high above 100%. The hardest part is keeping easy days easy.
Worked example
On 6 hours (360 min) a week in 5 sessions at an 80/20 split with 5% threshold: easy time is 360 × 0.80 = 288 min (4:48:00) and hard time 72 min (1:12:00), split into 18 min at threshold and 54 min at high intensity. The average easy time per session is 288 ÷ 5 = 57.6 min (57:36). The suggested week is 1 hard session of about 1 h 32 min (72 min hard plus 20 min warm-up and cool-down) and 4 easy sessions of about 67 min each ((288 − 20) ÷ 4 = 67). The Polarization Index is log10(0.80 ÷ 0.05 × 0.15 × 100) = log10(240) = 2.38, so the plan is polarized.
Sources: Stöggl & Sperlich (2015), The training intensity distribution among well-trained and elite endurance athletes, Front. Physiol. · Treff et al. (2019), The Polarization-Index, Front. Physiol. · 80/20 Endurance — zone calculator (zones as % of LTHR)
Frequently asked questions
Is 80/20 measured in time or sessions?
The research mostly uses time (or distance) in each zone. Coaches often plan by sessions instead, with about four easy sessions for every hard one. Because warm-ups and recoveries are easy, an 80/20 session split usually comes out nearer 85–90% easy by time.
How do I know my easy pace is easy enough?
You should be able to talk in full sentences, and your heart rate should stay below about 90% of your lactate threshold heart rate (roughly zones 1–2 of a 5-zone system). If you are breathing hard, it is no longer easy.
What is the difference between polarized and pyramidal training?
Both keep most time easy. Polarized training puts the rest mainly above the second threshold (intervals) with very little threshold work, so high > threshold. Pyramidal training has more threshold than high-intensity time, which is common in marathon preparation.
What is the Polarization Index?
A single number from Treff et al. (2019): log10 of zone 1 ÷ zone 2 × zone 3 × 100, with each zone as a fraction of total time. Values above 2.00 indicate a polarized distribution. It is not defined when there is more high-intensity than easy time.
Does 80/20 suit beginners?
Yes. New runners benefit from a large base of easy aerobic work and are the most likely to run their easy days too hard. Keep hard sessions short and limited to one or two a week while fitness builds.
How many hard sessions should I do each week?
Most polarized plans use one to three. With five or fewer sessions a week, one or two hard sessions is typical; elite athletes training 10 or more times a week still rarely exceed three.
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This calculator is for educational purposes. Double-check important results before acting on them.