Choosing the Right Training Model: A Complete Guide to Science-Based Running Methods

When you open myRunningPace and see a dozen different calculators — VDOT, Critical Speed, Lactate Threshold, Polarized Training, the Norwegian Double Threshold method — it's reasonable to wonder: which one should I actually use?

Each model makes different assumptions about how the human body fatigues and adapts. Some predict race times. Some prescribe training intensities. Some structure your entire training week. The right tool depends on your goals, your data, and how much complexity you're willing to manage.

This guide walks through every major training model available on the site, explains what each does best, and helps you pick the right one for where you are right now.

Part 1: Prediction Models

These models take one or more race results and produce training paces and/or race predictions. They live in the Training Pace Calculator and the Race Time Predictor.

VDOT (Jack Daniels) — Training Zones from a Single Race

Jack Daniels' VDOT model derives a single number from your race time that represents your current aerobic fitness. From that number, it calculates five training zones (Easy, Marathon, Threshold, Interval, Repetition) — the same zones used by elite athletes and recreational runners alike.

Strengths:

• Works from a single race performance
• Produces the most physiologically grounded training zones
• Industry standard — tested against decades of athlete data
• Handles 1,500 m to marathon distances

Limitations:

• A single bad day or a particularly hilly course can skew your zone calculations
• Marathon predictions from short-distance VDOT carry significant uncertainty (±10–15%)
• Does not capture individual fatigue variation between runners with the same VO₂max

Use VDOT when you have a recent, well-paced 5K, 10K, or half marathon and you want training zones to structure your week.

Deep dive: Understanding VDOT and VO₂max

Riegel — Quick Cross-Distance Race Prediction

Peter Riegel's 1977 power law extends one race result to predict another:

$t_2 = t_1 \times \left(\frac{d_2}{d_1}\right)^{1.06}$

It's simple, requires minimal data, and is accurate for predictions within roughly two times the source distance. Its limitation is the fixed exponent: $1.06$ assumes an average fatigue profile that doesn't account for individual variation.

Strengths:

• Simple and transparent calculation
• Accurate for short-distance extrapolation
• Doesn't require an understanding of oxygen kinetics to interpret

Limitations:

• The $1.06$ exponent is a population average — your personal exponent may differ
• Increasingly inaccurate as the target distance diverges far from the source race
• Provides no training zone information on its own

Use Riegel when you want a quick cross-distance prediction and have a single clean race result.

Deep dive: How Race Predictors Work

Critical Speed — Multi-Race Precision

Critical Speed calculates two parameters from two or more race results:

$CS = \frac{d_2 - d_1}{t_2 - t_1}, \quad D' = d_1 - CS \times t_1$

These two numbers describe the fundamental shape of your personal endurance curve. $CS$ is the speed you can theoretically sustain indefinitely; $D'$ is the finite anaerobic buffer available above it.

Strengths:

• Accounts for individual fatigue profile directly
• Most accurate model in the 3–40 minute range
• Adaptable — updates rapidly as fitness changes
• Captures fast-twitch vs. slow-twitch bias that VDOT misses

Limitations:

• Requires at least two races at meaningfully different distances
• Very long races (marathon+) partially violate the hyperbolic model's assumptions

Use Critical Speed when you have data from 1,500 m through to 10K and want the most precise training paces and predictions for track and road races.

Deep dive: Critical Speed Explained

Hybrid — Safe Default for Uncertain Data

The Hybrid model combines Critical Speed and VDOT with a weighted average, adjusting for the runner's measured fatigue bias.

$\text{Hybrid Score} = w_{\text{VDOT}} \times \text{VDOT} + w_{\text{CS}} \times CS_{\text{normalised}}$

The weights are dynamically adjusted based on the Fatigue Index — a measure of how much your speed drops across different race distances relative to the average runner.

Strengths:

• Robust when you are unsure which single model is most accurate
• Fatigue-bias adjustment improves marathon predictions for speed-dominant runners
• Produces confident training zones even from imperfect data

Limitations:

• More complex calculation — harder to verify manually
• The averaging reduces sharpness; it will not outperform a well-calibrated CS model when CS data is good

Use Hybrid when you have multiple races but are uncertain about which model to trust, or when you want a conservative race-day target.

Part 2: Threshold-Based Training Methods

These methods focus on identifying your physiological thresholds — the precise intensities where your body shifts from aerobic to anaerobic metabolism — and using those thresholds to prescribe training.

Lactate Threshold (LT1 & LT2) — Train at Your Metabolic Boundaries

The lactate threshold approach identifies two critical intensity boundaries:

• LT1 (Aerobic Threshold): The intensity where lactate first begins to accumulate above resting levels (~2 mmol/L). This is your comfortable long-run pace — sustainable for 2–3 hours.
• LT2 (Anaerobic Threshold): The intensity where lactate accumulation accelerates sharply (~4 mmol/L). This is roughly your 1-hour race pace — the highest intensity you can sustain for an extended period.

Training based on these thresholds is more individualised than zone-based models because your LT1 and LT2 paces depend on your personal physiology, not on population averages.

Strengths:

• Directly targets the metabolic adaptations that improve endurance
• More personalised than VDOT zones for many runners
• Foundation for polarized and threshold-focused training philosophies
• Produces five physiologically distinct training zones (Recovery → Anaerobic)

Limitations:

• Lab-tested lactate values are ideal but expensive; race-based estimates are approximations
• LT1 and LT2 shift independently as fitness changes — needs periodic re-testing

Use Lactate Threshold when you want training intensities grounded in your personal metabolic response, especially if you're training for half marathon or marathon distances.

Deep dive: Lactate Threshold Training Explained

Polarized Training (80/20) — The Distribution That Elite Athletes Use

Polarized training is not a pace model — it's a training distribution model. It says that ~80% of your weekly volume should be below LT1 (easy), and ~20% should be at or above LT2 (hard). Almost nothing in between.

This contradicts the common recreational pattern of running most sessions at "moderate" effort (the so-called "grey zone" between LT1 and LT2). Research consistently shows that polarized distribution produces better aerobic adaptations than threshold-heavy or moderate-intensity programs.

Strengths:

• Supported by the largest body of endurance research
• Reduces overtraining risk by keeping most training genuinely easy
• Maximises aerobic adaptation while preserving high-intensity stimulus
• Forces honest easy-day discipline

Limitations:

• Requires knowing your LT1 pace (or heart rate) to enforce the boundary
• Easy running feels very slow, especially for competitive runners — adherence is hard
• Not a pace prescription — it tells you how much to run at each intensity, not what pace

Use Polarized Training when you have your lactate thresholds estimated and want to structure your weekly training distribution optimally.

Norwegian Double Threshold — Two Threshold Sessions per Day

The Norwegian method, popularised by Marius Bakken and the Ingebrigtsen brothers' coach Gjert Ingebrigtsen, takes threshold training to its logical extreme: two lactate threshold sessions in a single day, separated by recovery. The morning session targets LT2 with shorter, sharper intervals; the afternoon session targets LT1 with longer, steadier efforts.

The rationale: by splitting the threshold stimulus into two shorter bouts, each session stays within recoverable limits while the cumulative daily threshold volume exceeds what a single session could achieve.

Strengths:

• Maximises weekly threshold training volume without excessive per-session fatigue
• Proven at the elite level — the Ingebrigtsens, Jakob's WR in 1500m/mile
• Develops both LT1 and LT2 simultaneously in a single training day
• The calculator generates specific AM/PM session plans based on your fitness level

Limitations:

• Requires significant training maturity — not suitable for beginners
• Demands precise knowledge of your LT1 and LT2 paces
• Scheduling two quality sessions per day is impractical for many athletes
• Recovery requirements are high — nutrition and sleep must be dialled in

Use the Norwegian Method when you are an intermediate to advanced runner with established lactate thresholds, you can train twice daily, and you want to maximise threshold development for 5K to marathon racing.

Deep dive: The Norwegian Double Threshold Method

Part 3: Physiological Measurement Tools

These calculators don't prescribe training directly — they measure or estimate physiological markers that feed into the training models above.

VO₂max Estimation — Quantify Your Aerobic Engine

VO₂max (maximal oxygen uptake) is the gold-standard measure of aerobic fitness. Our estimator calculates it from either a race result (VDOT method) or from your resting and maximum heart rates (HR method), then provides a fitness classification and equivalent training paces.

Use it when you want a single number to benchmark your aerobic fitness over time, or to compare methods.

Try it: VO₂max Estimator · Deep dive: Understanding VDOT

Heart Rate Zones — Intensity by Heartbeat

Heart rate-based training uses your resting and maximum heart rates to define five intensity zones using the Karvonen (Heart Rate Reserve) method. This approach is useful when pace-based training is unreliable — on hilly terrain, in heat, at altitude, or during base-building phases when race data is stale.

Use it when you prefer heart rate monitoring over pace targets, or when environmental conditions make pace unreliable.

Try it: Heart Rate Zone Calculator · Deep dive: Maximum Heart Rate Guide

Lactate Accumulation Simulator — Visualise the Fade

The lactate simulator models how lactate accumulates during sustained efforts above your threshold. It helps you understand why the last 10K of a marathon feels exponentially harder, and where your personal "cliff" is.

Use it when you want to understand the physiology behind the fade and calibrate your race-day pacing.

Try it: Lactate Simulator

Part 4: The Decision Framework

Quick Reference Table

Decision Flow

What do you need?

├── Race time predictions
│   ├── One race → Riegel (Race Time Predictor)
│   └── Multiple races → Critical Speed or Hybrid (Training Pace Calculator)
│
├── Training paces / zones
│   ├── From race results → VDOT (Training Pace Calculator)
│   ├── From lactate thresholds → Lactate Threshold Calculator
│   └── From heart rate → Heart Rate Zone Calculator
│
├── Training structure
│   ├── Weekly volume distribution → Polarized Training Calculator
│   └── Daily session planning → Double Threshold Planner
│
└── Physiological benchmarks
    ├── Aerobic fitness → VO₂max Estimator
    └── Fatigue modelling → Lactate Simulator

How They All Fit Together

These tools aren't competing — they're complementary layers:

1. Estimate your fitness with the VO₂max Estimator or a recent race result
2. Find your thresholds with the Lactate Threshold Calculator (LT1 & LT2)
3. Choose your training paces from VDOT zones, lactate zones, or heart rate zones
4. Structure your week using the Polarized Training Calculator (80/20)
5. Plan your hard sessions using the Double Threshold Planner (if training twice daily)
6. Predict your races with the Race Time Predictor
7. Refine with race data — re-run the models after each race to track progression

The runners who improve fastest are the ones who use models as a starting hypothesis, observe their actual training response, and adjust. No model perfectly captures your biology on any given day. But together, they provide a remarkably complete picture of where you are and where you can go.

Further Reading

• Understanding VDOT and VO₂max
• How Race Predictors Work
• Critical Speed Explained
• Training Zones Explained
• Lactate Threshold Training Explained
• The Norwegian Double Threshold Method
• Maximum Heart Rate Guide