---
title: "Training Paces: Science and Calculation"
description: "Use a recent race result to estimate easy, marathon, threshold, interval and repetition paces. Learn how Daniels training zones fit into a running week."
canonical_url: "https://runima.fit/blog/training-paces"
---

> Index of every page on this site: [llms.txt](https://runima.fit/llms.txt)

<callout color="primary" icon="i-ph-lightning">

Running everything at a single moderate pace is a reliable route to stagnation for an already-trained runner. Descriptive studies of elite endurance athletes consistently show the same shape: a large easy majority, a small hard minority, and very little time in the middle — not hard work all the time.

</callout>

## Why training paces exist

Biological adaptation follows the principle of specificity. Each physiological system — cardiac stroke volume, capillary density, mitochondrial volume, lactate-clearance enzymes — has a specific intensity at which it is optimally stressed.

Be precise about what that does and doesn't imply. Moderate continuous running is not inert: in untrained people almost any consistent aerobic stimulus raises VO₂max and threshold. The problem is what it costs a runner who already trains regularly. Moderate work is fast enough to accumulate real autonomic and muscular fatigue, but not slow enough to be free recovery, nor fast enough to deliver the strongest threshold or VO₂max signal available for that fatigue. It's an opportunity-cost problem, not a "does nothing" problem — and it compounds when every run lands there.

Calculated training paces solve this by assigning every run a precise physiological objective, so each session stresses the right system while leaving enough recovery to absorb it.

<note icon="i-ph-info">

Three paces, three goals: Easy builds the aerobic foundation, Threshold raises the lactate ceiling, Intervals push the VO₂max limit. A moderate pace targets none of them precisely.

</note>

## The five Daniels training zones

Based on the work of exercise physiologist Jack Daniels and his Daniels-Gilbert formula, structured training is divided into five zones. Daniels defines each zone by the fraction of VO₂max it sustains; because oxygen cost rises faster than speed, the corresponding fraction of velocity at VO₂max (vVO₂max) is always the higher number of the two.

<card-group>
<card icon="i-ph-smiley" title="Easy (E) Pace">

59–74% VO₂max (≈68–78% of vVO₂max). The foundation of base-building and recovery — stimulates capillary growth, mitochondrial biogenesis, and cardiac stroke volume expansion. Should feel highly conversational; typically a 3:3 or 4:4 breathing rhythm.

</card>

<card icon="i-ph-target" title="Marathon (M) Pace">

75–84% VO₂max (≈84–86% of vVO₂max). Trains glycogen-sparing efficiency and lipid oxidation. Controlled but demanding — short phrases of conversation are possible.

</card>

<card icon="i-ph-trend-up" title="Threshold (T) Pace">

Daniels' published paces land at ≈88–90% VO₂max (≈90–92% of vVO₂max), the top of the 83–88% band usually quoted for this zone. Run as 20-min tempo runs or 5–15-min cruise intervals. Improves lactate clearance — one documented mechanism is upregulation of the MCT1/MCT4 lactate transporters. "Comfortably hard"; often a 3:3 breathing rhythm.

</card>

<card icon="i-ph-timer" title="Interval (I) Pace">

The tightest-defined zone of the five: Daniels' published I paces sit at 97.2% of VO₂max (≈97–99% of vVO₂max) at every fitness level, within a rounding error. Structured as 3–5 min repetitions with recovery no longer than the work interval. Maximizes aerobic power and cardiac output. Labored 2:2 breathing; conversation is impossible.

</card>

<card icon="i-ph-lightning" title="Repetition (R) Pace">

Supramaximal — the 400 m R paces in the table below work out to ~104–108% of vVO₂max, and the band climbs further for the shortest reps. Short 200–600m repeats with full recovery. Targets neuromuscular speed, stride power, and running economy.

</card>
</card-group>

<table>
<thead>
  <tr>
    <th>
      Zone
    </th>
    
    <th>
      Sustained VO₂max (%)
    </th>
    
    <th>
      vVO₂max (%)
    </th>
    
    <th>
      Primary Adaptations
    </th>
    
    <th>
      Practical Workout Structures
    </th>
    
    <th>
      Subjective Feel Cue
    </th>
  </tr>
</thead>

<tbody>
  <tr>
    <td>
      <u-badge className="whitespace-nowrap" color="neutral" variant="subtle">
        Easy (E)
      </u-badge>
    </td>
    
    <td>
      59%–74%
    </td>
    
    <td>
      ~68%–78%
    </td>
    
    <td>
      Angiogenesis, mitochondrial enzyme synthesis, ventricular hypertrophy.
    </td>
    
    <td>
      Continuous runs of 30–150 mins; recovery runs.
    </td>
    
    <td>
      Conversational; full sentences; 3:3–4:4 breathing.
    </td>
  </tr>
  
  <tr>
    <td>
      <u-badge className="whitespace-nowrap" color="info" variant="subtle">
        Marathon (M)
      </u-badge>
    </td>
    
    <td>
      75%–84%
    </td>
    
    <td>
      ~79%–86%
    </td>
    
    <td>
      Glycogen sparing, lipid metabolism, mental stamina at target race pace.
    </td>
    
    <td>
      Continuous steady runs or long repeats (e.g., 10k E + 15k M).
    </td>
    
    <td>
      Controlled tension; speaking in brief sentences.
    </td>
  </tr>
  
  <tr>
    <td>
      <u-badge className="whitespace-nowrap" color="success" variant="subtle">
        Threshold (T)
      </u-badge>
    </td>
    
    <td>
      88%–90%
    </td>
    
    <td>
      ~90%–92%
    </td>
    
    <td>
      MCT1/MCT4 transporter expression, blood lactate recycling.
    </td>
    
    <td>
      20-min continuous tempo runs or 5-to-15-min cruise intervals.
    </td>
    
    <td>
      Comfortably hard; speaking in short phrases; 3:3 breathing.
    </td>
  </tr>
  
  <tr>
    <td>
      <u-badge className="whitespace-nowrap" color="primary" variant="subtle">
        Interval (I)
      </u-badge>
    </td>
    
    <td>
      ~97.2%
    </td>
    
    <td>
      ~97%–99%
    </td>
    
    <td>
      Maximizing stroke volume, cardiac output, and VO₂max ceiling.
    </td>
    
    <td>
      3-to-5-minute repetitions with recovery ≤ the work interval.
    </td>
    
    <td>
      Hard, labored effort; gasping; 2:2 breathing.
    </td>
  </tr>
  
  <tr>
    <td>
      <u-badge className="whitespace-nowrap" color="error" variant="subtle">
        Repetition (R)
      </u-badge>
    </td>
    
    <td>
      Supramaximal
    </td>
    
    <td>
      ~104%–108%
    </td>
    
    <td>
      Stride power, motor unit recruitment, running economy.
    </td>
    
    <td>
      200m to 600m track repeats with full, long recoveries.
    </td>
    
    <td>
      Smooth, relaxed, fast sprinting; focusing on form.
    </td>
  </tr>
</tbody>
</table>

<tip icon="i-ph-percent">

E and M zones cover ~80% of weekly volume; T, I, and R zones cover only ~20%. Daniels also caps each quality zone separately: T work at roughly 10% of weekly volume, I work at 8% (or 10 km, whichever is smaller), and R work at 5% (or 8 km). These ceilings exist because the limit on quality training is how much of it you can recover from, not how much you can survive.

</tip>

## What "aerobic pace" actually means

"Aerobic pace" maps directly to Easy (E) pace in the Daniels system. It's the intensity where lactate production and clearance stay in balance, so blood lactate holds near resting values instead of climbing — the region below the first lactate threshold (LT1). LT1 is commonly marked near ~2.0 mM, but the exact value is individual; the defining feature is a stable, non-rising lactate curve, not a specific number. Aerobic metabolism supplies nearly all the ATP here — glycolysis never switches off entirely.

<note icon="i-ph-info">

Running at a true aerobic pace should feel entirely conversational. If you can't finish a sentence without pausing for breath, you've crossed LT1 and are no longer training the targeted aerobic base.

</note>

For a runner with a 45-minute 10K (VDOT ~45), the Easy pace range is 5:34–6:07 per kilometer. Running faster shifts energy production toward glycolysis and accumulates fatigue without improving base fitness.

Consistent Easy running triggers four key adaptations:

- **Capillarisation:** VEGF-driven growth of new capillaries around muscle fibers, reducing the diffusion distance for oxygen.
- **Mitochondrial biogenesis:** Upregulation of citrate synthase and cytochrome c oxidase increases fat-oxidation capacity and glycogen sparing.
- **Plasma volume expansion:** Higher plasma volume reduces blood viscosity, improves microcirculation, and enhances heat dissipation.
- **Cardiac stroke volume expansion:** Eccentric hypertrophy of the left ventricle pumps more blood per beat, lowering heart rate at any submaximal intensity over time.

## How training paces are calculated from a race result

Training zones can't be reliably derived from a lab test alone because performance depends on both VO₂max and running economy (RE) — the energy cost of running at a given speed. In [Conley and Krahenbuhl (1980)](https://pubmed.ncbi.nlm.nih.gov/7453514/), 12 elite male runners from the top 19 finishers of a national 10K were tested. Within that narrow group — mean VO₂max 71.7 mL/kg/min — running economy explained 65.4% of the variation in race time, while VO₂max itself correlated with performance at just r = −0.12 (p = 0.35). The caveat matters: this is a small, deliberately homogeneous sample, so it shows that VO₂max stops discriminating once a field is already fast, not that VO₂max is unimportant in general.

The two traits are also largely independent: [Shaw et al. (2015)](https://pmc.ncbi.nlm.nih.gov/articles/PMC4388468/) measured 168 trained distance runners, with 54 followed longitudinally, and found economy and VO₂max only weakly related (r ≈ 0.25–0.33 cross-sectionally, 0.35–0.44 longitudinally) — over 85% of the variance unexplained, in the authors' own words. Note the sign, too: the correlation with oxygen *cost* was positive, meaning higher-VO₂max runners in that sample were, if anything, marginally *less* economical. Knowing one tells you little about the other — which is exactly why a lab VO₂max number alone can't set your paces.

VDOT bypasses this by using race time as input — implicitly capturing running economy — then back-calculating a functional VO₂max to derive vVO₂max and all five training zones.

**Recent Race Performance (Time & Distance) → VDOT Score → vVO₂max → Target Training Paces**

<tip icon="i-ph-calculator">

VDOT pace zones are more stable than heart rate day-to-day. Heat, sleep debt, caffeine, and dehydration can each move HR by several beats per minute at the same velocity, and cardiac drift can add 5% or more over a long run — enough to push a genuinely easy pace into a higher HR zone without the effort having changed. The trade-off runs the other way too: on a hot day or a hilly course, holding the prescribed pace raises the true physiological cost above the intended zone. Use pace as the default anchor, and let effort and HR override it in extreme conditions.

</tip>

Enter a recent all-out effort into the [Training Pace Calculator](https://runima.fit/tools/training-pace-calculator) to get your zones. If you're targeting an upcoming race, the [Race Time Predictor](https://runima.fit/tools/race-time-predictor) projects finish times across distances from the same VDOT.

- Optimize aerobic efficiency: [how to maintain a lower heart rate while running](https://runima.fit/blog/run-faster-lower-heart-rate).
- Metabolic thresholds in depth: [Lactate Threshold](https://runima.fit/blog/lactate-threshold).
- Why raw lab metrics mislead: [The VO₂max Trap](https://runima.fit/blog/the-vo2max-trap).

## The training paces lookup table

Equivalent race times and training paces (min:sec per kilometer) across VDOT 35–65, derived from the Daniels-Gilbert formula. Marathon pace is simply the marathon column divided by 42.195 km.

Threshold pace is *not* 10K pace. Daniels anchors T near the effort you could race for about an hour — roughly 88–90% of VO₂max — which works out a few seconds per kilometre slower than 10K pace: 4:38 vs 4:31 at VDOT 45, 3:26 vs 3:18 at VDOT 65. Interval pace runs the other way, slightly *faster* than 5K race pace (4:16 vs 4:22 per km at VDOT 45), because a 5K is raced just below 100% of VO₂max.

In fact every zone here reduces to a fixed fraction of VO₂max, recovered by checking Daniels' published paces against the oxygen-cost curve: **Easy 69.9%–62.0%, Threshold 87.9%, Interval 97.2%**. Those three barely move across the whole VDOT range — Interval varies by 0.04 percentage points. Marathon and Repetition drift slightly with fitness, rising roughly 0.08 and 0.15 points per VDOT unit respectively, because a faster runner spends less time on the road for the same race and can hold a larger fraction of capacity.

The one place the rules break is the bottom of the range. At VDOT 35 the published Easy and Threshold paces are both faster than the constants predict (~12 and ~6 s/km), since Daniels declines to let easy running get arbitrarily slow for a beginner.

Values are rounded to the nearest second, so expect ±1–2 s/km against other published tables. Simplified online calculators often substitute 10K pace for T and 5K pace for I, which is why their zones can sit 5–10 s/km away from these.

<table>
<thead>
  <tr>
    <th>
      VDOT
    </th>
    
    <th>
      5K
    </th>
    
    <th>
      Marathon
    </th>
    
    <th>
      Easy (E) (min/km)
    </th>
    
    <th>
      Marathon (M)
    </th>
    
    <th>
      Threshold (T)
    </th>
    
    <th>
      Interval (I)
    </th>
    
    <th>
      Repetition (R) (min/400m)
    </th>
  </tr>
</thead>

<tbody>
  <tr>
    <td>
      35
    </td>
    
    <td>
      27:00
    </td>
    
    <td>
      4:16:03
    </td>
    
    <td>
      6:35 – 7:14
    </td>
    
    <td>
      6:05
    </td>
    
    <td>
      5:35
    </td>
    
    <td>
      5:14
    </td>
    
    <td>
      2:00
    </td>
  </tr>
  
  <tr>
    <td>
      40
    </td>
    
    <td>
      24:08
    </td>
    
    <td>
      3:49:45
    </td>
    
    <td>
      6:07 – 6:43
    </td>
    
    <td>
      5:27
    </td>
    
    <td>
      5:06
    </td>
    
    <td>
      4:42
    </td>
    
    <td>
      1:47
    </td>
  </tr>
  
  <tr>
    <td>
      45
    </td>
    
    <td>
      21:48
    </td>
    
    <td>
      3:28:07
    </td>
    
    <td>
      5:34 – 6:07
    </td>
    
    <td>
      4:56
    </td>
    
    <td>
      4:38
    </td>
    
    <td>
      4:16
    </td>
    
    <td>
      1:36
    </td>
  </tr>
  
  <tr>
    <td>
      50
    </td>
    
    <td>
      19:57
    </td>
    
    <td>
      3:10:49
    </td>
    
    <td>
      5:07 – 5:38
    </td>
    
    <td>
      4:31
    </td>
    
    <td>
      4:15
    </td>
    
    <td>
      3:55
    </td>
    
    <td>
      1:28
    </td>
  </tr>
  
  <tr>
    <td>
      55
    </td>
    
    <td>
      18:22
    </td>
    
    <td>
      2:56:01
    </td>
    
    <td>
      4:45 – 5:13
    </td>
    
    <td>
      4:10
    </td>
    
    <td>
      3:56
    </td>
    
    <td>
      3:38
    </td>
    
    <td>
      1:21
    </td>
  </tr>
  
  <tr>
    <td>
      60
    </td>
    
    <td>
      17:03
    </td>
    
    <td>
      2:43:25
    </td>
    
    <td>
      4:25 – 4:53
    </td>
    
    <td>
      3:52
    </td>
    
    <td>
      3:40
    </td>
    
    <td>
      3:23
    </td>
    
    <td>
      1:15
    </td>
  </tr>
  
  <tr>
    <td>
      65
    </td>
    
    <td>
      15:54
    </td>
    
    <td>
      2:32:35
    </td>
    
    <td>
      4:09 – 4:34
    </td>
    
    <td>
      3:37
    </td>
    
    <td>
      3:26
    </td>
    
    <td>
      3:10
    </td>
    
    <td>
      1:10
    </td>
  </tr>
</tbody>
</table>

<tip icon="i-ph-lightbulb">

If your VDOT falls between two rows, default to the slower bracket for the first six weeks of a training cycle. Pushing paces beyond current fitness reduces metabolic effectiveness and accelerates chronic fatigue.

</tip>

## The 80/20 rule: how to distribute training across zones

Two related but distinct ideas often get merged here. The **80/20 rule** says roughly 80% of weekly volume should be easy and 20% hard. **Polarized training** is stricter: it says the hard 20% should sit clearly *above* the second threshold, with the moderate middle — which includes Threshold pace — kept deliberately small. Daniels' own prescriptions are not strictly polarized; they lean pyramidal, using a meaningful block of T work. The practical common ground, and the part the evidence supports best, is that the easy majority must actually be easy.

[Seiler and Kjerland (2006)](https://pubmed.ncbi.nlm.nih.gov/16430681/) measured 11 well-trained junior cross-country skiers across 318 sessions and found ~75% of *sessions* fell below the first ventilatory threshold, ~8% in the middle zone, ~17% above the second — the observation that named the polarized model. Their blood-lactate subset landed in the same place (71% / 7% / 22%). [Stöggl and Sperlich (2014)](https://pmc.ncbi.nlm.nih.gov/articles/PMC3912323/) tested it in a 9-week randomized trial of 48 well-trained endurance athletes (41 completed, ~10 per group): the polarized group gained +11.7% VO₂peak, ahead of HIIT (+4.8%, also statistically significant), while threshold-only and high-volume groups showed no significant change. [Esteve-Lanao et al. (2005)](https://journals.lww.com/acsm-msse/fulltext/2005/03000/how_do_endurance_runners_actually_train_.22.aspx) tracked eight subelite runners over a six-month macrocycle and found time accumulated in the easy zone associated with better cross-country race times, and [their 2007 randomized follow-up](https://pubmed.ncbi.nlm.nih.gov/17685689/) put it to the test over five months: 12 runners assigned to emphasize low-intensity volume (80/12/8) improved their 10.4 km time more than those emphasizing the between-thresholds zone (67/25/8) — −157 s vs −122 s, p = 0.03.

Worth keeping in perspective: these are small samples (8–12 athletes, or roughly that per group), several drawn from cross-country skiing rather than running, and both groups in the 2007 trial improved substantially — the moderate-emphasis runners still took two minutes off. The evidence supports easy-dominant distribution as the better default, not as the only arrangement that works.

The mechanism: Easy running drives structural cardiovascular adaptations (capillarisation, ventricular remodeling) with minimal autonomic fatigue, preserving the runner's capacity to execute quality sessions at exactly the intensities needed.

<note icon="i-ph-chart-pie">

For 50 km/week: ~40 km should be Easy (including warm-ups, cool-downs, long runs), with only ~10 km of quality work. If hard sessions feel underwhelming, the culprit is usually Easy runs being too fast — not insufficient hard work.

</note>

## The grey zone trap

The most common self-coaching mistake is compressing all training into a middle intensity: the "grey zone." Too fast for recovery, too slow to drive adaptation.

<caution icon="i-ph-warning">

**The Grey Zone Trap:** The grey zone is the span between the fast end of your Easy range and your Threshold pace — for a VDOT 45 runner, everything between 5:34 and 4:38 per kilometre, a window nearly a minute wide. It feels productive — you sweat, you're tired — but it blocks muscular recovery without delivering the full structural benefit of easy running or the lactate stimulus of true threshold work.

One clarification, because that window contains Marathon pace (4:57 for the same runner): the grey zone is defined by *intent*, not by the pace itself. M-pace work is deliberate, budgeted, and race-specific. The same pace run by accident, on a day meant to be easy, is the grey zone. What makes it a trap is drift — not the number on the watch.

</caution>

Runners stuck here enter quality sessions carrying fatigue, forcing Intervals and Tempo runs below the required intensity. They lose the structural benefits of easy running *and* miss the high-velocity stimulus needed to raise their aerobic ceiling.

<tip icon="i-ph-chat-circle">

Quick self-check: on your next "easy" run, try holding a full conversation. If you can't speak in complete sentences without pausing, slow down — you're in the grey zone.

</tip>

## How to put the zones into a training week

For a runner with VDOT 45 (recent 5K ~21:50) and a 50 km week, the 80/20 split gives roughly 40 km Easy and 10 km quality.

<table>
<thead>
  <tr>
    <th>
      Day
    </th>
    
    <th>
      Workout
    </th>
    
    <th>
      Objective
    </th>
  </tr>
</thead>

<tbody>
  <tr>
    <td>
      Mon
    </td>
    
    <td>
      8 km Easy (5:34–6:07 /km)
    </td>
    
    <td>
      Active recovery, clear metabolic waste
    </td>
  </tr>
  
  <tr>
    <td>
      Tue
    </td>
    
    <td>
      3 km E + 4×1200 m T (4:38 /km, 1 min jog rest) + 3 km E
    </td>
    
    <td>
      Accumulate lactate-threshold time
    </td>
  </tr>
  
  <tr>
    <td>
      Wed
    </td>
    
    <td>
      Rest
    </td>
    
    <td>
      —
    </td>
  </tr>
  
  <tr>
    <td>
      Thu
    </td>
    
    <td>
      9 km E + 6×100 m R strides (~1:37/400 m, walk-back rest)
    </td>
    
    <td>
      Aerobic base + neuromuscular coordination
    </td>
  </tr>
  
  <tr>
    <td>
      Fri
    </td>
    
    <td>
      3 km E + 4×1000 m I (4:15 /km, 3 min jog rest) + 3 km E
    </td>
    
    <td>
      Maximize VO₂max stimulus
    </td>
  </tr>
  
  <tr>
    <td>
      Sat
    </td>
    
    <td>
      12 km Easy
    </td>
    
    <td>
      Muscular resilience + fat-oxidation
    </td>
  </tr>
  
  <tr>
    <td>
      Sun
    </td>
    
    <td>
      Rest
    </td>
    
    <td>
      —
    </td>
  </tr>
</tbody>
</table>

That totals 50.4 km: 41.0 km Easy (warm-ups, cool-downs, base, long run) and 9.4 km quality — an 81/19 split. The quality work also stays inside Daniels' per-zone ceilings: 4.8 km of T is 9.5% of the week, and 4.0 km of I is 8.0%. Those two caps, not the 80/20 headline, are what actually constrain how a week is built.

<tip icon="i-ph-arrows-clockwise">

Not every week needs a quality session. A cutback week every 3–4 weeks (60–70% of volume, Easy only) lets accumulated structural adaptations consolidate before the next loading block.

</tip>

Applying calculated paces transforms running from a willpower contest into a structured science. Precision beats effort: every session delivers a targeted physiological signal, and recovery is where speed is actually built.

*This article is for general education and isn't medical or coaching advice.*

## References

1. Daniels J. (2013). *Daniels' Running Formula* (3rd ed.). Human Kinetics.
2. [Seiler S, Kjerland GØ (2006)](https://pubmed.ncbi.nlm.nih.gov/16430681/). Quantifying training intensity distribution in elite endurance athletes: is there evidence for an "optimal" distribution? *Scandinavian Journal of Medicine & Science in Sports*, 16(1), 49–56.
3. [Stöggl T, Sperlich B (2014)](https://pmc.ncbi.nlm.nih.gov/articles/PMC3912323/). Polarized training has greater impact on key endurance variables than threshold, high intensity, or high volume training. *Frontiers in Physiology*, 5, 33.
4. [Esteve-Lanao J, San Juan AF, Earnest CP, Foster C, Lucia A (2005)](https://journals.lww.com/acsm-msse/fulltext/2005/03000/how_do_endurance_runners_actually_train_.22.aspx). How do endurance runners actually train? Relationship with competition performance. *Medicine & Science in Sports & Exercise*, 37(3), 496–504.
5. [Esteve-Lanao J, Foster C, Seiler S, Lucia A (2007)](https://pubmed.ncbi.nlm.nih.gov/17685689/). Impact of training intensity distribution on performance in endurance athletes. *Journal of Strength and Conditioning Research*, 21(3), 943–949.
6. [Conley DL, Krahenbuhl GS (1980)](https://pubmed.ncbi.nlm.nih.gov/7453514/). Running economy and distance running performance of highly trained athletes. *Medicine & Science in Sports & Exercise*, 12(5), 357–360.
7. [Shaw AJ, Ingham SA, Atkinson G, Folland JP (2015)](https://pmc.ncbi.nlm.nih.gov/articles/PMC4388468/). The correlation between running economy and maximal oxygen uptake: cross-sectional and longitudinal relationships in highly trained distance runners. *PLoS ONE*, 10(4), e0123101.

## Sitemap

See the full [sitemap](https://runima.fit/sitemap.md) for all pages.