80% of training at low intensity, 20% at high intensity. The polarised model outperforms threshold training. Science has confirmed it since 2006, including in swimming.
Most club coaches have their groups swim at a "comfortable pace" almost every session. Not too slow (that would seem unproductive), not too fast (that would be exhausting). This comfortable middle zone looks like serious work. Yet this is precisely what exercise science identifies as the most common trap in swimming.
To summarise: 80/20 training in swimming means dedicating 80% of volume to low intensity and 20% to high intensity. Almost nothing in between. This polarised model produces greater performance gains than threshold training, according to several controlled studies. And 320+ coaches using Padlie already structure their sessions around this principle.
In the early 2000s, Stephen Seiler, professor at the University of Agder (Norway), analysed the training logs of elite athletes in cross-country skiing, rowing, cycling and swimming. He found a consistent pattern across all disciplines: approximately 75 to 80% of volume was completed at low intensity, and 15 to 20% at high intensity, with minimal work in the middle zone.
"Elite endurance athletes converge on a training intensity distribution of approximately 80% below the first lactate threshold and 20% above the second lactate threshold. Very little training is performed in the 'gray zone' between the two thresholds."
— Stephen Seiler, International Journal of Sports Physiology and Performance, 2010 (PMID 20861519)
Seiler and Kjerland had documented this pattern in 2006 in the Scandinavian Journal of Medicine & Science in Sports (16(1):49–56) with elite junior cross-country skiers. The measured distribution: 75% Zone 1, 7% Zone 2, 17% Zone 3 by number of sessions. This was not a theoretical prescription — it was an empirical observation. The best athletes were naturally doing this.
The threshold model is what most clubs practise: a lot of swimming at a sustained pace, around CSS or slightly below. It is effective in the short term. Over time, it generates a slight chronic fatigue that prevents both adequate recovery and real progress at high intensity.
| Critère | Polarised model (80/20) | Threshold model |
|---|---|---|
| Zone 1 (< 2 mmol/L) | ~80% | ~60–65% |
| Zone 2 (2–4 mmol/L) | < 5% | ~25–30% |
| Zone 3 (> 4 mmol/L) | ~15–20% | ~10% |
| Hard work placed | Above lactate threshold | At lactate threshold |
| Recovery quality | High | Moderate to low |
| Overtraining risk | Low | Moderate to high |
The critical difference: in the polarised model, hard sessions are genuinely hard, with blood lactate above 4 mmol/L. In the threshold model, they stay around 3 to 4 mmol/L. This distinction is physiological: moderate intensity does not sufficiently activate the AMPK pathway responsible for VO2max adaptations and lactate clearance.
A controlled trial published in the International Journal of Sports Physiology and Performance in 2019 (PMID 30040002) is the reference study directly in swimming. Twenty-two elite junior swimmers (17 ± 3 years) alternated 6 weeks of polarised training and 6 weeks of threshold training in a crossover design.
Results over 100 m: the polarised group (81% / 4% / 15%) improved their times by +0.97% ± 1.02%. The threshold group (65% / 25% / 10%): +0.09% ± 0.94%. Ten times less improvement. Without significant differences in physiological markers (VO2max, blood lactate at fixed speed), the decisive factor was recovery: polarised swimmers reported significantly lower fatigue and higher perceived recovery.
This is the central paradox of the polarised model: reducing moderate intensity improves performance. The reason is metabolic. Zone 2 work, between the two lactate thresholds, is intense enough to deplete glycogen stores and raise cortisol, but not intense enough to trigger maximum adaptations. It accumulates debt without producing the dividend.
In practice: a swimmer training five times per week at a comfortable pace often ends up in a state of slight chronic fatigue. Hard sessions are never truly hard, because they arrive fatigued. Easy sessions are never truly easy, because they feel reluctant to slow down. Everything happens in the grey zone of Zone 2, where neither the aerobic base nor high-intensity capacity truly progresses.
For the cellular mechanisms behind this stagnation, the article on Zone 2 and lactate threshold in swimming explains in detail why a lactate spike inhibits fat oxidation for 20 to 30 minutes and how to programme low aerobic blocks.
The calculation is straightforward. For a group with 5 sessions per week, one session represents 20% of volume. The target distribution: 4 light sessions (Zone 1, technical work, volume) for every 1 genuinely hard session (high intensity above the second threshold).
In light sessions, the goal is sustained continuity at a stable pace, between 75 and 85% of the swimmer's CSS. These sessions are also the ideal time for technical work: low intensity allows focus on the stroke without interference from fatigue. If speed drifts upward during the session, the pace was too high.
In the hard session, the rule is clear intensity. Repetitions above the second threshold, at 110 to 115% of CSS, with sufficient recovery between sets to maintain that intensity. The article on VO2max protocols in swimming covers session formats suited to this intensity for different competition distances.
The 80/20 model is not universal across all events. A systematic review on intensity distribution in elite swimmers (PMID 33952709, IJSPP 2021) shows clear differences: sprint swimmers (50–100 m) tend toward a polarised or threshold model, middle-distance swimmers (200–400 m) toward a hybrid model, and distance swimmers (800–1500 m) toward a pyramidal model, where threshold volume remains more important.
For a coach training a mixed group, the practical recommendation is to maintain the 80/20 base for general training sessions, and adapt the hard 20% according to target events as competition approaches. The season structure in macrocycles remains the framework within which this distribution evolves across mesocycles.
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