Training intensity distribution: three zones, five zones and 80/20
Understand polarized, pyramidal and threshold-centered training, how sessions and minutes differ, and what studies can actually say about an 80/20 plan.
A threshold model places boundaries at independently established first and second thresholds. Its middle Zone 2 is between those thresholds.
Anchored to two thresholds
Three threshold zones
Below the first threshold, between thresholds, and above the second. Lactate and ventilatory methods depend on their test protocol; this example uses entered lactate-threshold HR anchors.
145 and 170 bpm are fictional example inputs. Enter thresholds established independently through suitable testing; this explorer does not find your thresholds.
1Low intensityBelow the first thresholdBelow 145 bpm
2Between thresholdsFirst threshold to below the second145–169 bpm
3High intensityAt or above the second threshold170+ bpm
A simplified three-zone model: below, between and above two thresholds. Whole-beat display puts the boundary beat in the higher zone. Testing protocols and real responses are more complex than these cutoffs.
Threshold model updated: first threshold 145, second threshold 170 beats per minute.
Anchored to percentages
Five app zones
Familiar labels make a training log easier to read. The app’s estimate uses these percentage cutoffs; custom or coach-defined ranges can differ.
Z1
Recovery50–<60% of the selected anchor
Z2
Endurance60–<70% of the selected anchor
Z3
Tempo70–<80% of the selected anchor
Z4
Threshold80–<90% of the selected anchor
Z5
High intensity90% and above of the selected anchor
For HRmax, the anchor is maximum HR. For heart-rate reserve, the percentage is applied to HRmax − HRrest, then HRrest is added. Below 50% forms the app’s below-zone bucket.
Zone 2 in the three-zone threshold model sits between LT1 and LT2. The five-zone Zone 2 label is often used for easy endurance training, but a percentage calculation cannot prove that you are below LT1. Read the system, anchor and measurement method alongside the number.
These models have no universal one-to-one conversion. They also do not define the exact moderate, heavy and severe physiological intensity domains; those require their own threshold and critical-power context.
Three-zone threshold model in focus. Both models remain visible.
Keep the three-zone research model separate
The three-zone threshold model uses below-first, between-thresholds and above-second intensity bands. The app's five-zone model uses percentage bands. More labels do not mean more directly measured physiological landmarks, and fewer labels do not make a model useless.
A five-zone chart cannot be converted into a threshold-based chart merely by joining colors. You need independently established thresholds and the underlying measurements. The model explorer places the systems side by side to explain the definitions; its example thresholds do not measure your own.
In a polarized three-zone distribution, most training is below the first threshold, the above-second share exceeds the middle share, and relatively little lies between thresholds. In a pyramidal distribution, the low share is still largest, while the middle share exceeds the high share. A threshold-centered pattern places more emphasis on the middle.
These definitions describe proportions; they do not prescribe one exact total duration, session count or event plan. The same shape can accompany substantially different weekly loads. It also matters whether the shape is maintained throughout a block or changes with its purpose.
Consider an illustrative week with four easy sessions and one interval session. Counting main session goals gives four out of five easy sessions. Counting planned segment minutes assigns the interval session's preparation and recoveries to lower effort bands, and its planned hard work to higher bands. The percentages can differ even though the athlete did exactly the same training.
Recorded heart-rate minutes can place some work in a lower band and some recovery in a higher one, because response timing and measurement do not exactly track changes in output. A session's average heart rate introduces another view and may hide its peaks and recovery periods. Choose the denominator before interpreting a ratio: sessions, recorded heart-rate minutes, planned work minutes or another metric. Keep that choice constant across comparisons.
Observing an athlete's low-intensity emphasis is useful, but it does not isolate which part caused performance. Controlled interventions answer a more specific comparison. A nine-week trained-athlete trial favored polarized training for several laboratory measures; a later runner trial suggested small gains from changing distribution, while warning that most changes were below the smallest detectable change.
The systematic evidence is outcome-dependent. The 2024 meta-analysis reported a pooled VO2peak advantage for polarized approaches while other outcomes showed no clear pooled advantage. These findings support an informed choice, not the claim that exactly 80% easy training is mandatory for everyone.
First describe the actual pattern. Then ask whether it matches the intended goal, available time and ability to repeat the routine. Was steady work deliberate? Did easier sessions become harder? Did the session count stay constant while total duration rose? Those questions are more useful than awarding a week a score from one ratio.
Keep sport and experience visible. High-volume trained athletes, occasional exercisers and people returning to activity face different planning questions. The guides and tools can organize the information, but they cannot establish an individual's optimum from percentages alone.
Name the zone definitions before comparing a week with a paper.
Show absolute minutes as well as percentages.
Keep the counting method consistent.
Consider the training block, not just an isolated week.
Sources and further reading
The examples in this guide illustrate training concepts. Percentage bands and planning heuristics are identified as conventions; they do not measure your individual thresholds. The research library describes study populations, methods, outcomes, and limitations.
Oliveira, Boppre and Fonseca · 2024 · Systematic review and meta-analysis of controlled training interventions; searches through October 2022.
Practical interpretation: Assess the outcome you want to improve. A VO2peak advantage does not establish a universally superior race plan or a mandatory 80/20 split.
Limits: Interventions and comparators differed, participants were predominantly male, and study durations were generally short. Publication year does not mean the search included 2024 studies.
Filipas, Bonato, Gallo and Codella · 2022 · Four-group randomized trial over 16 weeks, comparing fixed distributions and changes between them.
Practical interpretation: The distribution can change across a season. Treat periodization as part of the comparison rather than asking only which single pattern wins.
Limits: Most significant changes were below the smallest detectable change; the relative VO2peak trend was largely attributed to weight variation. The trained male sample limits transfer to other runners.
Jamnick, Pettitt, Granata, Pyne and Bishop · 2020 · Critical review of measurement methods and their relationship to exercise-intensity domains.
Practical interpretation: Name the method and measurement. Do not treat LT2, a fixed lactate value, FTP and critical power as automatically equivalent.
Limits: Method validity for acute responses does not itself establish which prescription produces the best long-term training adaptation.
Seiler and Kjerland · 2006 · Observational training analysis using three ventilatory-threshold zones, heart rate, session effort and lactate measurements.
Practical interpretation: State whether a distribution counts sessions or time, and whether zones mean a three- or five-zone system.
Limits: Small, selected male athlete sample without a randomized comparator. Describing successful athletes' training cannot establish the optimum for all exercisers.
