What is training intensity distribution?
How your weekly running time is divided across easy, moderate and hard zones. The shape of that distribution predicts adaptation better than total volume alone.
Training intensity distribution, or TID, describes the proportion of training time spent in each of three zones: Zone 1 below LT1, Zone 2 between the thresholds, and Zone 3 above LT2. It is the structural question underneath most training debates — not how much you run, but how that running is spread across intensities.
Three named shapes dominate the literature. Pyramidal distributions put the most time in Zone 1, less in Zone 2 and least in Zone 3, in a descending staircase. Polarized distributions concentrate in Zones 1 and 3 with very little Zone 2. Threshold-focused distributions load Zone 2 heavily. Elite endurance athletes, measured across sports, overwhelmingly use pyramidal or polarized shapes.
The consistent finding is that a large Zone 1 base is common to every successful model — the disagreement is only about how to spend the remaining 15–20%. That is a much narrower argument than online discussion suggests, and for a marathon specifically the pyramidal shape has strong support because the race itself is run in the Zone 1–2 boundary region.
The practical implication is that adding hard sessions to a week that lacks easy volume rarely works. The hard work is only sustainable on top of the base, which is why so many plans that look aggressive on paper fall apart in week five.
Key numbers
| Zone 1 share | ~75–85% | common to all successful models |
|---|---|---|
| Common shapes | pyramidal, polarized | used by most elite endurance athletes |
Work it out for yourself
Marathon periodization planner — Compare pyramidal, polarized and threshold distributions over a full build.
Frequently asked questions
Is polarized training better than pyramidal?
For the marathon specifically, pyramidal has at least as much support, because race pace itself sits in the zone polarized training deliberately avoids. Both work; both depend far more on the large easy base they share than on the difference between them.
How do I measure my own distribution?
Divide time — not distance — by zone across a typical training week. Time is the right unit because a 40-minute easy run and a 40-minute interval session represent very different loads over very different distances.
Sources
- Stöggl & Sperlich (2015). The training intensity distribution among well-trained and elite endurance athletes. Frontiers in Physiology.
- Seiler (2010). What is best practice for training intensity and duration distribution in endurance athletes? International Journal of Sports Physiology and Performance.
Related explainers
Glossary: TID (Training Intensity Distribution)