How to use the weekly zone distribution calculator
Enter the total training time you logged for the week in hours and minutes, then the share that fell in zone 1 low, zone 2 moderate and zone 3 high intensity. The tool returns the time spent in each zone. The 80, 5 and 15 defaults are a commonly cited distribution placed there as a starting point, so replace them with your own numbers. If the three shares do not add to 100.0%, the tool reports the total and stops.
The polarization index is the value proposed by Treff and colleagues: the shares are converted to fractions and the index is log10(zone 1 รท zone 2 ร zone 3 ร 100). A value above 2.00 is read as polarized, but the authors also require zone 3 > zone 2 along with zone 1 > zone 2 and zone 1 > zone 3, and they hold that the index should not be computed when zone 3 exceeds zone 1. With zone 2 at 0 the tool substitutes 0.01 and says so on screen. With zone 3 at 0 the logarithm is undefined and no index is produced, as of October 2026.
Polarized training is usually described as roughly 75 to 80% low intensity, about 5% at threshold and 15 to 20% high, though sources disagree on the high share, putting it at 12 to 15% in some places and 15 to 20% in others. The 2.00 mark is itself disputed: a 2023 commentary in the same journal argued that the threshold of 2 was inferred from a two-dimensional figure that is hard to interpret. The distribution data also comes mainly from Nordic sports, the same review describes swimming and cycling as pyramidal, and there are objections that the evidence for world-class runners following an 80 to 20 split is weak.
There are limits. Session-level splits and which day the hard work belongs on are not calculated; only the weekly totals are. Whether the zone boundaries were set by heart rate, power or lactate changes the shares for identical training, and no conversion between those is supported. A higher index does not mean better training, and no distribution is recommended over another.
Frequently Asked Questions
No. They are a commonly cited distribution used as a starting point, and sources split on the high-intensity share, putting it at 12 to 15% or 15 to 20%. Entering the shares you actually logged fits the purpose of this calculation better.
It does not mean that. The index only summarizes in one number whether the middle of the three bands is thin, and the 2.00 mark itself drew a 2023 commentary arguing it was inferred from a figure that is hard to interpret.
Yes. When zone 3 exceeds zone 1 the authors hold that the index should not be computed, so only a notice appears, and when zone 3 is 0 the logarithm is undefined. When zone 2 is 0 the tool substitutes 0.01 and reports that substitution.