We Run Ultras

(2) Polarised Training Is Useful but Incomplete for Mountain Ultras

By Francesco//9 min read/Training science & durability

The specificity problem

Polarised training places most training below the first ventilatory threshold (Zone 1), a smaller share above the second threshold (Zone 3), and little between them. It can improve aerobic measures and has a legitimate place in an ultrarunner's year. The narrower thesis is that intensity distribution is incomplete as a model for mountain-ultra preparation: it says little about durability, time on feet, climbing economy or downhill eccentric loading, all of which determine whether an aerobic ceiling remains usable late in the race.

How hard ultras are

The "ultras are a Zone 2 race" framing is not well supported by field data. A 2018 study in the Journal of Sports Sciences measured time-in-zone during a 65 km mountain ultra and found roughly 86% of race time spent below VT1 — Zone 1 by any standard model. Fornasiero et al. (2017, Frontiers in Physiology) measured mean intensity at the Tor des Géants 330 km race at 57.3% VO₂peak, and one case study at Western States 100 recorded approximately 51% VO₂max during a representative running segment. The pattern is consistent: intensity decreases sharply with duration, from around 60–70% VO₂max in 6-hour events to 40–50% in 24-hour events. For elite athletes with a high aerobic threshold, much of that race time falls in Zone 1. The Zone 2 specificity argument is real for recreational athletes whose aerobic threshold is lower, but it does not apply universally.

The evidence gap

The research base is thinner than the popularity of the model implies, but it is not empty. Oliveira et al. (2024, Sports Medicine) found a small advantage for polarised training in VO₂peak, concentrated in shorter interventions and highly trained athletes; effects on time-trial performance were not significant. More directly, Pérez et al. assigned 20 recreational ultra-endurance runners to 12 weeks of polarised or threshold training. The polarised group improved running economy and time to exhaustion, but the study was small, allocation was not described as random, and it measured laboratory surrogates rather than an ultramarathon. Polarised training therefore has ultra-relevant evidence, not ultra-race proof.

The comparison model also matters. Polarised training often looks favourable against threshold-heavy programmes that place much more work between the ventilatory thresholds. That does not establish superiority over a well-designed pyramidal plan, nor does it tell a runner how to distribute intensity during a terrain-specific block. Oliveira's meta-analysis found substantial variation in sports, training status, intervention length and zone quantification. A label can conceal as much as it describes.

Durability is a separate adaptation

Durability is the resistance to deterioration in physiological characteristics during prolonged exercise. Matomäki et al. (2023) compared 10 weeks of low- and high-intensity cycling in 35 sedentary or recreationally active adults. Both groups improved a composite durability measure similarly, while VO₂max improved only after high-intensity training. This is not an ultrarunning trial, and three hours of cycling does not reproduce a mountain race. It does demonstrate that improvements in the aerobic ceiling and resistance to drift are separable. A programme can improve one without proving superiority for the other.

Durability is also metric-specific. Heart-rate drift, ventilation, substrate use, perceived effort and the speed sustainable below a threshold can deteriorate at different rates. A runner may preserve one while losing another. That is why a fresh VO₂max test and a short time trial are incomplete checks for an athlete whose decisive problem appears after six hours. A standardised long run with late-stage pace, heart rate and perceived effort can add the missing information without pretending to be a laboratory test.

The neuromuscular mismatch

Metabolic zone distributions miss a second problem entirely. Millet et al. (2011) assessed 22 runners after a 166 km mountain ultra and found knee-extensor maximal voluntary contraction reduced by 35% and plantar-flexor contraction by 39%; creatine kinase rose from 144 to 13,633 IU/L. Force recovered within two weeks in the 11 runners who completed follow-up testing. The study documents the neuromuscular cost of the event, not the optimal training dose. The coaching inference is nevertheless strong: cycling and flat running can satisfy an intensity target while providing little of the progressive eccentric loading imposed by long descents.

Implication for training

The strongest counterargument is that VO₂max still matters: Sabater-Pastor et al. (2023) found that velocity at VO₂max explained substantial variance in a 166 km trail race. An aerobic ceiling is real, but prediction does not identify the best way to train every determinant. A review of 175 elite endurance training distributions found 89 pyramidal and 65 polarised, with large differences by sport and season. The practical choice is not polarised versus specific training. Keep enough high-intensity work to develop the ceiling, then protect the durability work that resembles the event: long easy volume, sustained climbs, progressive descents and fuelling under fatigue. If those sessions are repeatedly displaced to preserve a neat zone ratio, the model has become the constraint.

Sources

Race physiology and intensity profiles

  1. Vernillo G, et al., "Physiological intensity profile of a 65‑km mountain ultra‑marathon" Journal of Sports Sciences, 2018 https://doi.org/10.1080/02640414.2017.1374707

  2. Fornasiero A, et al., "The Energetics during the World's Most Challenging Mountain Ultra-Marathon (Tor des Géants)" Frontiers in Physiology, 2017 https://doi.org/10.3389/fphys.2017.01003

  3. Stuempfle KJ, Hoffman MD, "Indirect Calorimetry During Ultradistance Running: A Case Report (Western States 100)" Journal of Sports Science and Medicine, 2006 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3827564/

  4. Garbisu-Hualde A, Santos-Concejero J, "What are the Limiting Factors During an Ultra-Marathon? A Systematic Review" Journal of Human Kinetics, 2020 https://doi.org/10.2478/hukin-2019-0102

  5. Wolfarth B, et al., "Influence of a 100-mile ultramarathon on heart rate and heart rate variability" BMJ Open Sport and Exercise Medicine, 2020 https://doi.org/10.1136/bmjsem-2020-001005

  6. Esteve-Lanao J, et al., "How Do Humans Control Physiological Strain during Strenuous Endurance Exercise?" PLOS ONE, 2008 https://doi.org/10.1371/journal.pone.0002943

Polarized training research

  1. Stöggl T, Sperlich B, "Polarized training has greater impact on key endurance variables than threshold, high intensity, or high volume training" Frontiers in Physiology, 2014 https://doi.org/10.3389/fphys.2014.00033

  2. Oliveira PS, Boppre G, Fonseca H, "Comparison of Polarized Versus Other Types of Endurance Training Intensity Distribution on Athletes' Endurance Performance" Sports Medicine, 2024 https://doi.org/10.1007/s40279-024-02034-z

  3. Rosenblat MA, Perrotta AS, Vicenzino B, "Polarized vs. Threshold Training Intensity Distribution on Endurance Sport Performance: A Systematic Review" Journal of Strength and Conditioning Research, 2019 https://doi.org/10.1519/JSC.0000000000002618

  4. Filipas L, et al., "Effects of plyometric training on different 8-week training intensity distributions in well-trained endurance runners" Scandinavian Journal of Medicine and Science in Sports, 2022 https://doi.org/10.1111/sms.14257

  5. Seiler KS, Kjerland GØ, "Quantifying training intensity distribution in elite endurance athletes" Scandinavian Journal of Medicine and Science in Sports, 2006 https://doi.org/10.1111/j.1600-0838.2004.00418.x

  6. Pérez A, et al., "Effect of two different intensity distribution training programmes on aerobic and body composition variables in ultra-endurance runners" European Journal of Sport Science, 2019 https://doi.org/10.1080/17461391.2018.1539124

  7. Muñoz I, et al., "Eleven‑Week Preparation Involving Polarized Intensity Distribution Is Not Superior to Pyramidal Distribution in National Elite Rowers" Frontiers in Physiology, 2017 https://doi.org/10.3389/fphys.2017.00515

Durability and metabolic adaptation

  1. Maunder E, et al., "The Importance of 'Durability' in the Physiological Profiling of Endurance Athletes" Sports Medicine, 2021 https://doi.org/10.1007/s40279-021-01459-0

  2. Matomäki P, et al., "Durability is improved by both low and high intensity endurance training" Frontiers in Physiology, 2023 https://doi.org/10.3389/fphys.2023.1128111

  3. Hunter B, Muniz-Pumares D, "Durability of Parameters Associated With Endurance Running Performance in Marathoners" European Journal of Sport Science, 2025 https://doi.org/10.1002/ejsc.70073

  4. Maunder E, et al., "Peak fat oxidation is positively associated with vastus lateralis CD36 content, fed-state exercise fat oxidation, and endurance performance" European Journal of Applied Physiology, 2021 https://doi.org/10.1007/s00421-021-04820-3

  5. Meixner B, et al., "Zone 2 Intensity: A Critical Comparison of Individual Variability" Translational Sports Medicine, 2025 https://doi.org/10.1155/tsm2/2008291

  6. Maunder E, et al., "Prolonged exercise reduces power output at the moderate-to-heavy intensity transition" European Journal of Applied Physiology, 2022 https://doi.org/10.1007/s00421-022-05036-9

Neuromuscular demands of mountain running

  1. Millet GY, et al., "Neuromuscular Consequences of an Extreme Mountain Ultra-Marathon" PLOS ONE, 2011 https://doi.org/10.1371/journal.pone.0017059

  2. Degache F, et al., "Alterations of Neuromuscular Function after the World's Most Challenging Mountain Ultra-Marathon (Tor des Géants)" PLOS ONE, 2013 https://doi.org/10.1371/journal.pone.0065596

  3. Lloria-Varella J, et al., "Assessing Physiological Durability in Trail Runners: A Terrain-Specific Protocol" International Journal of Sports Physiology and Performance, 2025 https://doi.org/10.1123/ijspp.2025-0307

  4. Partyka M, Waśkiewicz Z, "Musculoskeletal Consequences of Ultra-Marathon Races: A Systematic Narrative Review" Frontiers in Physiology, 2021 https://doi.org/10.3389/fphys.2021.738665

Training intensity distribution and elite athletes

  1. Sperlich B, Matzka M, Holmberg HC, "The proportional distribution of training by elite endurance athletes at different exercise intensity" Frontiers in Sport and Active Living, 2023 https://doi.org/10.3389/fspor.2023.1258585

  2. Rivera-Kofler T, et al., "Anthropometric Characteristics, Training Intensity Distribution and Physiological Profile of an Elite Trail Runner: A Longitudinal Case Study" International Journal of Morphology, 2024 https://doi.org/10.4067/s0717-95022024000200416

  3. Roche D, "Eight Takeaways From Kilian Jornet's 2022 Training Data" Trail Runner Magazine, 2022 https://www.trailrunnermag.com/training/trail-tips-training/kilian-jornet-training-data/

  4. COROS, "Inside Kilian Jornet's Training Data" COROS, 2025 https://coros.com/stories/more-than-splits/c/kilian-jornet-training

  5. Jaén-Carrillo D, Margarit-Boscà A, "Reverse periodization in ultratrail: Road to the 2023 World Championships" Ciencias del Deporte, 2024 https://doi.org/10.36950/2024.4ciss039

Performance determinants

  1. Sabater-Pastor F, et al., "VO₂max and Velocity at VO₂max Play a Role in Ultradistance Trail-Running Performance" International Journal of Sports Physiology and Performance, 2023 https://doi.org/10.1123/ijspp.2022-0275

  2. Rapp E, et al., "The effect of XC-running race on determinants of performance: VO₂ at lactate threshold, fat utilization, and running economy" Frontiers in Physiology, 2025 https://doi.org/10.3389/fphys.2025.1647810

  3. Casado A, et al., "Does Lactate-Guided Threshold Interval Training Represent the Next Step in the Evolution of Distance Running Training?" International Journal of Environmental Research and Public Health, 2023 https://doi.org/10.3390/ijerph20053782

Coaching and applied sources

  1. Roche D, "The Exciting Complexity of Threshold Training for Trail Running" Trail Runner Magazine, 2023 https://www.trailrunnermag.com/training/trail-tips-training/the-exciting-complexity-of-threshold-training-for-trail-running/

  2. Hutchinson A, "The Case For (and Against) Polarized Training" Outside Online, 2022 https://www.outsideonline.com/health/training-performance/polarized-training-debate/

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