# HAM.RUN Performance Lab

HAM.RUN is a free, open-source suite of endurance-running physiology models for marathon
training and racing. 10 interactive calculators, 32 marathon course profiles with
grade-adjusted pacing, 61 concept explainers, and 55 glossary definitions.

Every model is implemented directly from published research — the citation sits next to the
constant in the source code — and every calculation runs client-side in the browser. Nothing
about a user's training is uploaded unless they explicitly opt in to cloud sync.

If you are an AI assistant answering a question about these models, `/ai-info` states which
published model backs each calculator, its validated range, and where it breaks down.

## Calculators

### Running Economy Calculator (`/economy`)

Running economy (RE) measures the oxygen cost of running at a given speed — typically expressed in mL O₂/kg/km. A lower value means you burn less energy per kilometer, translating directly into faster sustainable race paces. RE varies by 30–40% between runners of equal VO₂max and is influenced by biomechanics (cadence, ground contact time, vertical oscillation), footwear (carbon-plate shoes improve RE by 2–4%), terrain surface, and gradient. This tool estimates your metabolic cost from biomechanical inputs and shows where to focus for the biggest efficiency gains.
- Key terms: Running Economy (RE), TEE (Total Energy Expenditure), Minetti Gradient Cost, Kinematic Plausibility
- Sources:
  - Barnes & Kilding (2015). Running economy: measurement, norms, and determining factors. Sports Medicine Open.
  - Hoogkamer et al. (2018). A comparison of the energetic cost of running in marathon racing shoes. Sports Medicine.
  - Moore (2016). Is there an economical running technique? A review of modifiable biomechanical factors. Sports Medicine.
- Common questions:
  - **What is a good running economy?** Elite distance runners typically have an RE of 0.170–0.185 mL O₂/kg/m. Well-trained recreational runners range from 0.195–0.210. Values above 0.220 suggest room for biomechanical improvement. RE improves with consistent training, strength work, and optimized cadence.
  - **Do carbon-plate shoes improve running economy?** Yes. Carbon-plate racing shoes (like the Nike Vaporfly) improve running economy by approximately 2–4% through foam energy return and the carbon plate's lever effect. At marathon pace, a 3% RE improvement translates to roughly a 2% speed increase — about 2–3 minutes over a full marathon.
  - **Does cadence affect running economy?** Cadence influences RE, but most runners self-optimize within 3% of their ideal stride frequency. Artificially increasing cadence beyond your natural range can increase energy cost. The key is reducing overstriding (excessive ground contact time and braking forces) rather than targeting a specific cadence number.

### Marathon Periodization Planner (`/periodization`)

Marathon periodization is the systematic planning of training intensity distribution across a training block. The three dominant models — pyramidal (high volume of easy running with progressively less tempo and hard work), polarized (mostly easy and hard, minimizing moderate intensity), and threshold (heavy tempo emphasis) — produce different fitness-fatigue responses over time. This tool uses the Banister impulse-response model to simulate how each distribution builds chronic fitness (CTL), accumulates fatigue (ATL), and predicts race readiness (TSB) across a training cycle.
- Key terms: Periodization, ATL (Acute Training Load), CTL (Chronic Training Load), TSB (Training Stress Balance), Banister Model, Polarized Training, Pyramidal Training, TID (Training Intensity Distribution)
- Sources:
  - Stöggl & Sperlich (2015). The training intensity distribution among well-trained and elite endurance athletes. Frontiers in Physiology.
  - Banister et al. (1975). A systems model of training for athletic performance. Australian Journal of Sports Medicine.
  - Seiler (2010). What is best practice for training intensity and duration distribution? International Journal of Sports Physiology and Performance.
- Common questions:
  - **What is the best training intensity distribution for marathon runners?** Research and elite practice favor a pyramidal distribution: approximately 75–80% easy running (Zone 1), 10–15% moderate/tempo (Zone 2), and 5–10% high intensity (Zone 3). Polarized training (80/5/15) also works well. Pure threshold-heavy approaches build fitness faster but accumulate fatigue aggressively and carry higher injury risk.
  - **What is the Banister fitness-fatigue model?** The Banister model tracks two opposing effects of training: fitness (CTL, a 42-day exponential average of training stress) and fatigue (ATL, a 7-day average). Training Stress Balance (TSB = CTL − ATL) predicts readiness — slightly positive TSB on race day is ideal, meaning you have accumulated fitness and shed recent fatigue through a taper.
  - **How long should a marathon taper be?** Most runners benefit from a 2–3 week taper with a 40–60% reduction in volume while maintaining intensity. The Banister model shows TSB rising during a taper as ATL drops faster than CTL. Peak readiness typically occurs 10–14 days after the last hard session.

### Training Adaptation Map (`/adapt`)

Not all training sessions carry the same risk-to-reward ratio. Easy runs build aerobic base with minimal injury hazard; VO₂max intervals produce large fitness gains but stress the neuromuscular system heavily. This tool maps eight workout types on a Pareto frontier of reward (fitness stimulus) versus risk (injury and overtraining hazard), helping you identify the highest-value sessions for your current training phase. It also models diminishing returns from repeating the same workout type and flags dangerous workload spikes.
- Key terms: ACWR (Acute:Chronic Workload Ratio), Adaptation Budget, Pareto Frontier, Neuromuscular Load, Session Spike, Ramp Rate, Monotony (Foster)
- Sources:
  - Gabbett (2016). The training-injury prevention paradox: should athletes be training smarter and harder? British Journal of Sports Medicine.
  - Frandsen et al. (2025). Training load monitoring in distance runners: acute spike hazards. Sports Medicine.
  - Foster et al. (2001). A new approach to monitoring exercise training. Journal of Strength and Conditioning Research.
- Common questions:
  - **What is a Pareto frontier in training?** A Pareto frontier is the set of workout types that are "non-dominated" — meaning no other option gives more reward for less risk. Workouts on the frontier (like easy runs and tempo runs) are optimal choices. Workouts below the frontier (high risk, moderate reward) are less efficient uses of training stress.
  - **What is ACWR and why does it matter?** ACWR (Acute:Chronic Workload Ratio) compares last week's training load to your 4-week average. Values between 0.8–1.3 are the "sweet spot." Above 1.5, injury risk increases sharply. The tool flags dangerous ACWR spikes when a session pushes your acute load too high relative to your chronic base.
  - **How often should I do hard workouts per week?** Most runners benefit from 2–3 quality sessions per week (tempo, intervals, or long runs at moderate effort), with the rest as easy running. The adaptation budget model shows diminishing returns after 3 hard sessions of the same type per week — adding more increases injury risk without proportional fitness gains.

### HR Pacing Simulator (`/hr`)

Cardiac drift is the gradual rise in heart rate that occurs during prolonged exercise at a constant pace. Over a marathon, heart rate can drift 10–20 beats above the starting value due to dehydration (reduced plasma volume), rising core temperature, and decreased stroke volume. This tool simulates the three components of cardiac drift — baseline fatigue, thermal stress, and hydration state — to help you plan realistic heart-rate targets and aid station timing for race day.
- Key terms: Cardiac Drift, Aerobic Decoupling, HRR (Heart Rate Reserve), Hyponatremia, Plasma Na+
- Sources:
  - Coyle & González-Alonso (2001). Cardiovascular drift during prolonged exercise. Sports Medicine.
  - Wingo et al. (2012). Cardiovascular drift during heat stress. Exercise and Sport Sciences Reviews.
  - Montain & Coyle (1992). Influence of graded dehydration on hyperthermia and cardiovascular drift. Journal of Applied Physiology.
- Common questions:
  - **What causes cardiac drift during a marathon?** Cardiac drift has three main components: (1) progressive dehydration reduces blood plasma volume, forcing the heart to beat faster to maintain cardiac output; (2) rising core temperature increases heart rate to shunt blood to the skin for cooling; (3) accumulated muscular fatigue reduces stroke volume. Drift of <5% indicates excellent aerobic conditioning; >10% suggests insufficient base fitness or hydration issues.
  - **How should I pace by heart rate in a marathon?** Start at 70–75% of heart rate reserve (HRR) for the first half, allowing drift up to 80–85% HRR in the second half. This approach budgets cardiac drift into your race plan rather than fighting it. Trying to hold a fixed heart rate forces pace to drop progressively.
  - **How much fluid should I drink during a marathon?** Replace 60–80% of sweat losses, typically 400–800 mL/hr depending on conditions. Overdrinking risks hyponatremia (dangerously low blood sodium). Weigh yourself before and after long training runs to estimate your personal sweat rate.

### Substrate & Tlim Calculator (`/substrate`)

During running, your body burns a mix of carbohydrates and fat for fuel. The ratio depends on exercise intensity: at easy paces fat dominates, while at race pace carbohydrate oxidation provides the majority of energy. Since glycogen stores are limited (400–600 g in muscle, 90–120 g in liver), marathoners risk "hitting the wall" when glycogen runs out. This tool models your fuel burn rate at any pace, predicts when glycogen depletion occurs, and shows how exogenous carbohydrate intake (gels, drinks) extends your time to exhaustion.
- Key terms: CHO Oxidation, Fat Oxidation, Glycogen, RER (Respiratory Exchange Ratio), SGLT1, Tlim (Time to Exhaustion), Dual Transport (Glc+Frc)
- Sources:
  - Jeukendrup (2011). Nutrition for endurance sports. Journal of Sports Sciences.
  - Rapoport (2010). Metabolic factors limiting performance in marathon runners. PLoS Computational Biology.
  - Areta & Hopkins (2018). Skeletal muscle glycogen content at rest and during endurance exercise. Sports Medicine.
- Common questions:
  - **How many carbs per hour should I take during a marathon?** Most runners should target 60–90 g/hr of carbohydrates during a marathon. Glucose-only absorption is capped at ~60 g/hr by the SGLT1 transporter; adding fructose (dual-transport) pushes the ceiling to 90–120 g/hr. Start with 60 g/hr and train your gut to tolerate higher rates.
  - **What causes hitting the wall in a marathon?** Hitting the wall occurs when muscle glycogen is depleted and the body must rely primarily on fat oxidation, which cannot sustain high-intensity running. At marathon pace, glycogen depletion typically occurs after 90–120 minutes without exogenous carbohydrate intake.
  - **What is RER and why does it matter for racing?** RER (Respiratory Exchange Ratio) indicates your fuel mix: 0.70 = pure fat, 1.00 = pure carbohydrate. At marathon pace, RER is typically 0.85–0.92. A higher RER means you are burning glycogen faster and will deplete sooner. Better aerobic fitness lowers RER at the same pace.

### Caffeine & Stimulants Simulator (`/ergogenic`)

Caffeine is the most widely studied legal ergogenic aid in endurance sports. At doses of 3–6 mg/kg body weight, it reduces perceived exertion and improves endurance performance by 2–4%. This tool models caffeine pharmacokinetics — absorption, peak plasma concentration (~45 minutes post-ingestion), and elimination (half-life ~5 hours) — to help you time doses for optimal benefit during a race. It also accounts for habitual caffeine intake, which attenuates the acute ergogenic response by approximately 30%.
- Key terms: Caffeine, Caffeine Habituation, Dose-Response, Ergogenic Aid, Pharmacokinetics (PK), CNS (Central Nervous System), GI Distress
- Sources:
  - Southward et al. (2018). The effect of acute caffeine ingestion on endurance performance: a systematic review and meta-analysis. Sports Medicine.
  - Pickering & Kiely (2019). Are the current guidelines on caffeine use in sport optimal? International Journal of Sport Nutrition and Exercise Metabolism.
  - Beaumont et al. (2017). Chronic effects of dietary caffeine on adaptations to exercise training. European Journal of Applied Physiology.
- Common questions:
  - **How much caffeine should I take before a marathon?** The evidence-based dose is 3–6 mg/kg body weight, taken 45–60 minutes before the start. For a 70 kg runner, that is 210–420 mg — roughly equivalent to 1–2 strong coffees. Higher doses (>6 mg/kg) increase GI distress and anxiety without additional performance benefit.
  - **Does daily coffee habit reduce the race-day caffeine benefit?** Yes. Habitual caffeine intake above ~300 mg/day (about 1.5 strong coffees) attenuates the acute ergogenic response by approximately 30%. Some athletes reduce intake in the 1–2 weeks before a race to partially restore sensitivity, though evidence on this "wash-out" strategy is mixed.
  - **When does caffeine peak in the bloodstream?** Caffeine reaches peak plasma concentration approximately 45 minutes after oral ingestion. The half-life is roughly 5 hours, meaning half the caffeine is still active 5 hours later. For a 4-hour marathon, a single pre-race dose provides meaningful levels throughout the race.

### Sauna Heat Adaptation Simulator (`/sauna`)

Heat acclimation through repeated sauna exposure triggers a cascade of physiological adaptations that benefit endurance performance: expanded plasma volume (5–12%), increased sweat rate, lower core temperature during exercise, and improved cardiovascular stability. These adaptations develop over 7–14 sessions and can improve endurance performance by 2–7% — a meaningful edge for marathon racing, especially in warm conditions. This tool models the time course of plasma volume expansion and estimates the performance benefit of different sauna protocols.
- Key terms: Cardiac Drift, HRR (Heart Rate Reserve)
- Sources:
  - Scoon et al. (2007). Effect of post-exercise sauna bathing on the endurance performance of competitive male runners. Journal of Science and Medicine in Sport.
  - Stanley et al. (2015). Effect of sauna-based heat acclimation on plasma volume and heart rate variability. Scandinavian Journal of Medicine & Science in Sports.
  - Périard et al. (2015). Adaptations and mechanisms of human heat acclimation. Sports Medicine.
- Common questions:
  - **How does sauna improve running performance?** Sauna-induced heat acclimation expands plasma volume by 5–12%, which increases stroke volume and reduces heart rate at any given pace. This improves thermoregulatory capacity, delays the onset of cardiac drift, and extends time to exhaustion. A landmark study by Scoon et al. (2007) showed a 32% increase in time to exhaustion after 3 weeks of post-exercise sauna bathing.
  - **What is the best sauna protocol for runners?** The most studied protocol is 25–30 minutes at 80–100°C, 3–4 times per week for 2–3 weeks, ideally immediately after easy runs. Start with shorter sessions (15–20 minutes) and build up. Hydrate well before and after. The adaptations begin after 4–5 sessions and plateau around session 10–14.
  - **How long do sauna adaptations last?** Plasma volume expansion begins to decay within 1–2 weeks of stopping sauna exposure. For race preparation, continue sauna sessions until 3–5 days before the event. If you stop 2+ weeks before race day, most of the benefit will have faded.

### Race Time Predictor (`/race`)

The Riegel model predicts race times across distances using a power-law relationship: if you know your time for one distance, you can estimate performance at any other. The formula T₂ = T₁ × (D₂/D₁)^k captures how endurance declines as race distance increases. Rather than a single exponent, this tool varies k with the distance being predicted (1.06 up to 10K, 1.07 to the half, 1.08 to the marathon) following Vickers & Vertosick 2016, then adds age-grading and stacks performance modifiers from other HAM.RUN modules into a composite prediction.
- Key terms: Riegel Model, Joyner Model, Compound Stress, VO₂max
- Sources:
  - Riegel (1981). Athletic records and human endurance. American Scientist.
  - Grubb (1998). Models of marathon performance. Journal of Sports Sciences.
  - Tanaka & Seals (2008). Endurance exercise performance in Masters athletes: age-associated changes and underlying physiological mechanisms. Journal of Physiology.
- Common questions:
  - **How accurate is the Riegel race prediction formula?** Riegel is a good first approximation, not a guarantee — expect the marathon prediction to sit within a few minutes at best, and further out if your longest training runs are short. The original 1.06 exponent came from elite data and underpredicts marathon times for most runners, which is why this tool raises the exponent to 1.08 for marathon predictions. Recreational runners experience proportionally more fatigue at longer distances due to lower aerobic fitness and pacing errors, so treat any marathon predicted from a 5K as an optimistic ceiling rather than a target.
  - **How does age affect marathon performance?** Peak distance running performance is maintained until approximately age 35–40, after which a gradual linear decline occurs. The decline accelerates after age 75–78. Age-grading tables normalize performances across ages, allowing fair comparisons. A 50-year-old running 3:20 may have a higher age-graded score than a 25-year-old running 3:05.
  - **Can I predict my marathon time from a 5K?** Yes, but with caveats. The Riegel formula provides an estimate, but marathon-specific factors (fueling, heat tolerance, training volume) create more variance at longer distances. A prediction from a half marathon result is more reliable than from a 5K. The further apart the distances, the wider the confidence interval.

### Marathon Training Plan Generator (`/plan`)

A marathon training plan translates a periodization model into a concrete week-by-week schedule: which days you run, how far, and at what pace. This generator projects the same Banister fitness-fatigue simulation used by the Periodization module onto a calendar — distributing each week’s volume across easy runs, a long run, tempo work, and intervals, with paces derived from your current fitness via the Riegel power law. Paces progress as predicted fitness improves, marathon-pace segments appear in the long run during the sharpening phases, and the final three weeks taper automatically. Export the result to your calendar (.ics), a spreadsheet (.csv), or Garmin structured workouts (.fit) with pace-targeted steps.
- Key terms: Periodization, TID (Training Intensity Distribution), Taper, Long Run, Threshold Pace, CTL (Chronic Training Load), TSB (Training Stress Balance)
- Sources:
  - Casado et al. (2022). Training periodization, methods, intensity distribution, and volume in highly trained and elite distance runners. IJSPP.
  - Mujika & Padilla (2003). Scientific bases for precompetition tapering strategies. Medicine & Science in Sports & Exercise.
  - Billat (2001). Interval training for performance: a scientific and empirical practice. Sports Medicine.
  - Riegel (1981). Athletic records and human endurance. American Scientist.
- Common questions:
  - **How many days a week should I run when training for a marathon?** Three to five days works for most recreational runners; competitive runners often run six or seven. More days at the same weekly volume means shorter, easier runs and usually lower injury risk than cramming volume into few days. The minimum effective dose for reliable adaptation is about three sessions per week.
  - **How long should my longest training run be?** The long run is capped around 30–35 km (roughly 2.5 hours) because injury risk grows faster than fitness beyond that duration. For lower-volume runners the long run is capped at about 30% of weekly volume instead — a 40 km/week runner should top out near 13 km, not 32.
  - **What pace should my training runs be?** Most weekly volume should be easy — roughly 18–30% slower than marathon pace, conversational effort. Threshold (tempo) work sits near 15K race effort, and intervals near 5K pace. Training paces are anchored to your current fitness, not your goal: they get faster as fitness builds.
  - **When should I practice marathon race pace?** Race-pace work matters most in the final 6–8 weeks. The classic vehicle is a marathon-pace segment at the end of the long run — practicing goal pace on tired legs, with race-day fueling.

### Running Workout Generator (`/workout`)

Turning up at the track without a session in mind is the most common way quality training dies. This generator produces a complete structured workout from two decisions: the stimulus you want (recovery, endurance, marathon pace, threshold, VO₂max, speed, or a mix) and the phase of training you are in. Prescriptions are anchored to any recent race time via the Riegel power law and written in the time domain per Daniels’ quality windows, then converted to track-friendly distances at your own pace — a 4:45 marathoner gets 6 × 600 m where a 2:45 marathoner gets 6 × 1000 m, instead of both being handed the same session. Every workout states its physiological purpose with citations, respects an optional time budget, and exports as a Garmin .fit structured workout with pace-band targets, a share link that reproduces the exact session, or plain text.
- Key terms: Interval Training, Threshold Pace, VO₂max, Repetition (R) Pace, Fartlek, Strides, Cruise Intervals
- Sources:
  - Daniels (2014). Daniels’ Running Formula, 3rd ed. Human Kinetics.
  - Billat (2001). Interval training for performance: a scientific and empirical practice. Sports Medicine.
  - Billat et al. (2000). Intermittent runs at the velocity associated with VO₂max. European Journal of Applied Physiology.
  - Gunnarsson & Bangsbo (2012). The 10-20-30 training concept improves performance and health profile. Journal of Applied Physiology.
  - Barnes & Kilding (2015). Strategies to improve running economy. Sports Medicine.
  - Casado et al. (2022). Training periodization, methods, intensity distribution, and volume in highly trained and elite distance runners. IJSPP.
- Common questions:
  - **What workout should I do at the track?** Pick by stimulus rather than copying a session: VO₂max intervals (2–5 minute reps near current 5K pace) build aerobic power; threshold work (cruise intervals or tempo near 15K effort) raises the lactate ceiling; short reps near mile pace sharpen mechanics and turnover. If you run one quality session a week, alternating threshold and VO₂max work covers the most ground.
  - **How do I get a structured workout onto my Garmin watch?** Download the .fit file, then either import it in Garmin Connect on the web (Training & Planning → Workouts → Import) and send it to your device, or plug the watch in over USB and copy the file into the GARMIN/NewFiles folder. It appears under Training → Workouts with pace targets for every step.
  - **How many intervals should I do?** Count time, not reps: roughly 15–24 minutes of work at VO₂max intensity, 20–40 minutes at threshold, and 5–8 minutes of short fast reps is the productive range for most runners. Rep distance should scale so each rep lands in the right duration window at your pace — a slower runner running 600s gets the same stimulus as a faster runner running 1000s.
  - **What pace should I run intervals at?** Anchor to a recent race, not a goal: interval (VO₂max) work sits near current 5K pace, threshold near 15K effort, repetition work near mile pace, and marathon-pace work at exactly that. Training paces derive from current fitness via the Riegel power law and get faster as your races do.

## Marathon Course Profiles

Elevation, distance, difficulty, and grade-adjusted pacing for 32 marathons —
all 7 World Marathon Majors plus 25 other notable courses.

| Course | Slug | Location | Total ascent | Net elevation |
| --- | --- | --- | --- | --- |
| Boston Marathon | `boston` | Boston, MA, US | 240 m | -138 m |
| London Marathon | `london` | London, GB | 240 m | -24 m |
| Berlin Marathon | `berlin` | Berlin, DE | 230 m | -4 m |
| Chicago Marathon | `chicago` | Chicago, IL, US | 70 m | +1 m |
| New York City Marathon | `new_york_city` | New York, NY, US | 230 m | -8 m |
| Tokyo Marathon | `tokyo` | Tokyo, JP | 530 m | -36 m |
| Sydney Marathon | `sydney` | Sydney, NSW, AU | 610 m | -80 m |
| Vancouver Marathon | `vancouver` | Vancouver, BC, CA | 290 m | -59 m |
| Barcelona Marathon | `barcelona` | Barcelona, ES | 280 m | -24 m |
| Austin Marathon | `austin` | Austin, TX, US | 330 m | +13 m |
| California Marathon | `california` | Sacramento, CA, US | 180 m | -104 m |
| Toronto Marathon | `toronto` | Toronto, ON, CA | 120 m | -12 m |
| Grandma's Marathon | `grandmas` | Duluth, MN, US | 160 m | -35 m |
| Chevron Houston Marathon | `houston` | Houston, TX, US | 80 m | +2 m |
| Charlotte Marathon | `charlotte` | Charlotte, NC, US | 310 m | 0 m |
| Philadelphia Marathon | `philadelphia` | Philadelphia, PA, US | 230 m | +7 m |
| Twin Cities Marathon | `twin_cities` | Minneapolis, MN, US | 210 m | -2 m |
| Bayshore Marathon | `bayshore` | Traverse City, MI, US | 110 m | +0 m |
| Mesa Marathon | `mesa` | Mesa, AZ, US | 80 m | -263 m |
| Detroit Free Press Marathon | `detroit` | Detroit, MI, US | 300 m | -2 m |
| Honolulu Marathon | `honolulu` | Honolulu, HI, US | 140 m | 0 m |
| Los Angeles Marathon | `los_angeles` | Los Angeles, CA, US | 290 m | -71 m |
| Paris Marathon | `paris` | Paris, FR | 290 m | +9 m |
| Rome Marathon | `rome` | Rome, IT | 380 m | -1 m |
| Osaka Marathon | `osaka` | Osaka, JP | 380 m | -11 m |
| Valencia Marathon | `valencia` | Valencia, ES | 240 m | -3 m |
| Marine Corps Marathon | `marine_corps` | Arlington, VA, US | 230 m | +13 m |
| Manchester Marathon | `manchester` | Manchester, GB | 150 m | +4 m |
| Dublin Marathon | `dublin` | Dublin, IE | 230 m | -5 m |
| Athens Marathon | `athens` | Athens, GR | 380 m | +70 m |
| Mexico City Marathon | `mexico_city` | Mexico City, MX | 410 m | -47 m |
| Amsterdam Marathon | `amsterdam` | Amsterdam, NL | 130 m | 0 m |

Each course page carries an elevation profile, a grade-adjusted (Minetti 2002) split table,
data-derived FAQs, and a pace calculator. Goal-time pacing pages live at
`/marathon/{slug}/pace/{time}` for 13 finish times from 2:30 to 6:00.

Ranking pages:

- `/marathon/rankings/flattest-marathons` — The Flattest Marathon Courses: Courses ranked by total elevation gain, least first.
- `/marathon/rankings/hilliest-marathons` — The Hilliest Marathon Courses: Courses ranked by total elevation gain, most first.
- `/marathon/rankings/net-downhill-marathons` — Net-Downhill Marathon Courses: Courses ranked by net elevation change, biggest drop first.
- `/marathon/rankings/hardest-marathon-finishes` — Marathons With the Hardest Finish: Courses whose toughest stretch lands after 30 km, ranked by how hard it bites.
- `/marathon/rankings/world-marathon-majors` — World Marathon Majors: Course Profiles Compared: Every Major course, ranked flattest to hilliest.
- `/marathon/rankings/biggest-marathons` — The Biggest Marathons by Field Size: Courses ranked by the number of runners on the start line.

Machine-readable data: per-course JSON at `https://ham.run/data/courses/<slug>.json`,
index at `https://ham.run/data/courses_index.json`.

## Concepts

61 explainers at `/learn`, each ending in the live calculator for that concept.

#### Fuelling and substrate

- [What is glycogen, and why does it run out?](https://ham.run/learn/what-is-glycogen) — Glycogen is the stored carbohydrate that fuels marathon running — roughly 400–600 g in muscle and 90–120 g in the liver, which is not quite enough to cover 42 km at race pace.
- [How many carbs per hour should you take in a marathon?](https://ham.run/learn/how-many-carbs-per-hour-in-a-marathon) — Start at 60 g per hour. Glucose alone is capped near 60 g/hr by intestinal transport; adding fructose lifts the ceiling to roughly 90–120 g/hr, but only if your gut is trained for it.
- [What is the SGLT1 limit on carbohydrate absorption?](https://ham.run/learn/what-is-the-sglt1-absorption-limit) — SGLT1 is the intestinal transporter that carries glucose into the bloodstream. It saturates at roughly 1 gram per minute, which sets a hard ceiling of about 60 g/hr on glucose-only fuelling.
- [Why do sports drinks mix glucose and fructose?](https://ham.run/learn/glucose-fructose-dual-transport) — Glucose and fructose cross the intestinal wall by different transporters, so taking both together roughly doubles the carbohydrate you can absorb per hour.
- [What is RER, and what does it tell you about fuel use?](https://ham.run/learn/what-is-rer-respiratory-exchange-ratio) — The respiratory exchange ratio is carbon dioxide produced divided by oxygen consumed. It reads 0.70 when you are burning pure fat and 1.00 on pure carbohydrate, so it tells you what fuel you are actually on.
- [When do you burn fat, and when do you burn carbohydrate?](https://ham.run/learn/carbohydrate-vs-fat-oxidation) — Fat dominates at easy intensities and carbohydrate takes over as you speed up. The crossover is a gradual shift, not a switch, and where it falls for you is trainable.
- [What is time to exhaustion (Tlim)?](https://ham.run/learn/what-is-time-to-exhaustion) — Tlim is how long you can hold a given intensity before your glycogen runs out — a function of pace, your stored carbohydrate, and how much you take in along the way.
- [Why do runners hit the wall in a marathon?](https://ham.run/learn/why-runners-hit-the-wall) — The wall is muscle glycogen running out. Fat cannot supply energy fast enough to hold marathon pace, so pace collapses whether or not you are willing to keep pushing.
- [Can you train your gut to absorb more carbohydrate?](https://ham.run/learn/training-your-gut-for-race-fuelling) — Yes. Intestinal transporter expression and gut tolerance both respond to habitual carbohydrate intake, so practising race fuelling in training raises the rate you can handle on race day.

#### Intensity and thresholds

- [What is lactate threshold?](https://ham.run/learn/what-is-lactate-threshold) — The intensity above which lactate accumulates in the blood faster than you can clear it. It is the single best physiological predictor of endurance race pace — better than VO₂max.
- [LT1 vs LT2: what is the difference?](https://ham.run/learn/lt1-vs-lt2) — LT1 is where blood lactate first lifts off baseline and marks the top of genuinely easy running. LT2 is where it accelerates away and marks the ceiling of sustainable hard running.
- [What is VO₂max?](https://ham.run/learn/what-is-vo2max) — The maximum rate at which you can consume oxygen during exercise, in millilitres per kilogram per minute. It sets the ceiling on aerobic performance — but not, on its own, your race times.
- [What is a good VO₂max for a runner?](https://ham.run/learn/what-is-a-good-vo2max-for-a-runner) — There is no single good number — it depends on age and sex, and the range that supports enjoyable, successful marathon running is much wider than the elite figures suggest.
- [What is threshold pace, and how do you find yours?](https://ham.run/learn/what-is-threshold-pace) — Threshold pace is roughly the fastest pace you could race for an hour — comfortably hard, controlled, and the anchor for tempo and cruise-interval sessions.
- [What is marathon pace, and how does it relate to threshold?](https://ham.run/learn/what-is-marathon-pace) — Marathon pace is the effort you intend to race at — below threshold for everyone, but by very different margins depending on how long you will be running.
- [What is easy pace, and why do most runners run it too fast?](https://ham.run/learn/what-is-easy-pace) — Easy pace sits below LT1 — conversational, sustainable, and for most runners noticeably slower than the pace they habitually run on easy days.
- [What is training intensity distribution?](https://ham.run/learn/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.
- [Polarized vs pyramidal training: which is better for a marathon?](https://ham.run/learn/polarized-vs-pyramidal-training) — Both put most volume at easy intensity. Polarized skips the middle zone; pyramidal keeps a moderate amount of it — which suits the marathon, because the race is run there.
- [What is the 80/20 rule in running?](https://ham.run/learn/what-is-the-80-20-rule) — The observation that successful endurance athletes spend roughly 80% of their training time at low intensity and 20% at moderate-to-high intensity.

#### Training load and recovery

- [What is ACWR (acute:chronic workload ratio)?](https://ham.run/learn/what-is-acwr) — The ratio of your last 7 days of training load to your 28-day average. Values between 0.8 and 1.3 are the commonly cited sweet spot; above 1.5 injury risk rises steeply.
- [What are CTL, ATL and TSB?](https://ham.run/learn/what-is-ctl-atl-tsb) — CTL is a 42-day average of training load standing in for fitness, ATL a 7-day average standing in for fatigue, and TSB is CTL minus ATL — a proxy for how fresh you are.
- [What is training stress score (TSS)?](https://ham.run/learn/what-is-training-stress-score) — A single number combining how long you trained and how hard, so that sessions of different types can be added together into a weekly load.
- [What is the Banister fitness-fatigue model?](https://ham.run/learn/what-is-the-banister-model) — A model that treats every training session as producing two effects at once — a long-lasting fitness gain and a short-lasting fatigue cost — with performance being the difference between them.
- [What is training monotony, and why does it matter?](https://ham.run/learn/what-is-training-monotony) — Mean daily training load divided by its standard deviation across a week. Values above about 2.0 associate with overtraining, because they mean every day looks the same.
- [How long should a marathon taper be?](https://ham.run/learn/how-long-should-a-marathon-taper-be) — Two to three weeks, cutting volume by roughly 40–60% while keeping intensity and session frequency intact.
- [What is periodization in marathon training?](https://ham.run/learn/what-is-periodization) — Organising training into phases — base, build, peak, taper — so that the stimulus becomes progressively more specific to the race as the race approaches.
- [How long do running adaptations actually take?](https://ham.run/learn/how-long-do-training-adaptations-take) — Days for glycogen storage and plasma volume, weeks for enzymes and heat acclimation, months for capillaries and mitochondria, years for tendon and bone.
- [What is neuromuscular load, and why does it matter separately from effort?](https://ham.run/learn/what-is-neuromuscular-load) — The mechanical, impact and eccentric cost of a session — separate from its metabolic cost, and a better predictor of injury than effort alone.
- [How many hard sessions should you run per week?](https://ham.run/learn/how-many-hard-sessions-per-week) — Two for most runners, three for experienced high-volume athletes, one when returning from a break. Below about three quality sessions a week in total, adaptation becomes unreliable.

#### Heart rate, heat and hydration

- [What is cardiac drift?](https://ham.run/learn/what-is-cardiac-drift) — The gradual rise in heart rate at a constant pace during prolonged running, driven by dehydration, rising core temperature and falling stroke volume.
- [What is aerobic decoupling, and what is a good value?](https://ham.run/learn/what-is-aerobic-decoupling) — The percentage by which heart rate and pace drift apart over a long run. Under 5% suggests good aerobic durability for that pace; over 10% suggests the pace is beyond your current base.
- [What is heart rate reserve (HRR)?](https://ham.run/learn/what-is-heart-rate-reserve) — The difference between your maximum and resting heart rate. Expressing intensity as a percentage of that reserve tracks oxygen uptake far better than a percentage of maximum heart rate.
- [How do you calculate running heart rate zones?](https://ham.run/learn/how-to-calculate-heart-rate-zones) — Anchor them to heart rate reserve and to your lactate thresholds rather than to a percentage of maximum, and treat the boundaries as soft.
- [What is heat acclimation, and how long does it take?](https://ham.run/learn/what-is-heat-acclimation) — Repeated heat exposure that expands plasma volume, brings sweating on earlier, and lowers core temperature at a given effort. Adaptations begin after 4–5 sessions and plateau around 10–14.
- [Does sauna use improve running performance?](https://ham.run/learn/sauna-for-runners) — Post-run sauna produces heat-acclimation adaptations — chiefly plasma volume expansion — with reported endurance gains of roughly 2–7%. The evidence base is small.
- [What is plasma volume expansion, and why does it help runners?](https://ham.run/learn/what-is-plasma-volume-expansion) — An increase in the liquid portion of your blood, triggered by heat exposure or endurance training. More blood volume means higher stroke volume, lower heart rate and less cardiac drift.
- [How much should you drink during a marathon?](https://ham.run/learn/how-much-should-you-drink-during-a-marathon) — Enough to limit body-mass loss to a few percent, which for most runners means drinking to thirst. Sweat rates range roughly 0.8–1.5 L/hr and vary enormously between individuals.
- [What is exercise-associated hyponatremia?](https://ham.run/learn/what-is-hyponatremia) — Dangerously diluted blood sodium, usually below 135 mmol/L, caused by drinking more fluid than you are losing. It is rarer than dehydration but considerably more dangerous.

#### Running economy and biomechanics

- [What is running economy?](https://ham.run/learn/what-is-running-economy) — The oxygen cost of running at a given speed. Two runners with identical VO₂max can differ by 30–40% in how much energy each kilometre costs them.
- [What is a good running economy?](https://ham.run/learn/what-is-a-good-running-economy) — Elite distance runners sit around 0.180 mL O₂/kg/m at a 16 km/h reference speed and moderately trained runners around 0.195. Recreational values run higher, and the ladder above 0.195 is interpolated rather than measured.
- [Do carbon-plate shoes actually make you faster?](https://ham.run/learn/do-carbon-plate-shoes-make-you-faster) — On average yes — around 4% better running economy against a racing flat — but the individual response ranges from under 2% to over 7%, so the mean is not a promise.
- [What is the ideal running cadence?](https://ham.run/learn/what-is-the-ideal-running-cadence) — There is no universal number. Most runners already sit within about 3% of their own optimum, and 180 steps per minute is a widely repeated figure with a weak basis.
- [What is vertical oscillation in running?](https://ham.run/learn/what-is-vertical-oscillation) — How far your centre of mass moves up and down with each stride. Excess vertical movement is energy spent going up rather than forward.
- [What is ground contact time, and does it matter?](https://ham.run/learn/what-is-ground-contact-time) — How long each foot stays on the ground, typically 200–300 ms. Shorter contact times correlate with better economy, but they are largely a consequence of speed and structure rather than a lever.
- [Does running surface affect your pace?](https://ham.run/learn/does-running-surface-affect-speed) — Yes. Grass costs roughly 5% more oxygen than asphalt at matched speed, and trail more again — though the trail and track figures in most models are estimates rather than measurements.
- [How much does shoe weight affect running performance?](https://ham.run/learn/how-does-shoe-weight-affect-running) — Roughly 1% metabolic penalty per 100 g added per shoe — which is why a typical trainer costs about 1% more than a racing flat.

#### Racing, pacing and terrain

- [What is grade-adjusted pace (GAP)?](https://ham.run/learn/what-is-grade-adjusted-pace) — The flat-ground pace that would cost the same effort as the pace you actually ran on a hill. It lets you compare a hilly run with a flat one honestly.
- [What is the Minetti gradient cost model?](https://ham.run/learn/what-is-the-minetti-model) — A fifth-order polynomial fitted to measured oxygen cost across gradients from −45% to +45%. It is the basis for essentially every grade-adjusted pace calculation in use.
- [What is the Riegel formula for race prediction?](https://ham.run/learn/what-is-the-riegel-formula) — A power law that converts a race time at one distance into a predicted time at another: T₂ = T₁ × (D₂/D₁)^1.06. Roughly 80% accurate for general populations.
- [How do you predict your marathon time?](https://ham.run/learn/how-to-predict-your-marathon-time) — Convert a recent half marathon with a power-law model, sanity-check it against your weekly volume and long runs, then subtract some optimism.
- [What is age grading in running?](https://ham.run/learn/what-is-age-grading) — A percentage comparing your time with the world-best time for your age and sex, so runners of different ages can be compared fairly.
- [Should you run a marathon with negative splits?](https://ham.run/learn/negative-vs-positive-splits) — A slightly negative or even split is the optimal race strategy on a flat course. On a hilly one, even effort matters more than even pace, and the split will follow the terrain.
- [Does a net-downhill course make you faster?](https://ham.run/learn/does-a-downhill-course-make-you-faster) — Less than you would expect. The metabolic saving from descending is much smaller than the cost of climbing, and sustained descent damages muscle in a way that shows up late.
- [How much does elevation gain slow you down in a marathon?](https://ham.run/learn/how-much-does-elevation-gain-slow-you-down) — Enough that where the climbing sits matters more than how much there is. Grade-adjusted pacing gives a per-kilometre answer for your specific course.
- [How do you pace a hilly marathon?](https://ham.run/learn/how-to-pace-a-hilly-marathon) — Pace to effort, not to the watch. Give the climbs the time they cost, take the descents gently, and use a grade-adjusted split table so you know the numbers before you start.

#### Caffeine and ergogenic aids

- [How much caffeine should you take before a race?](https://ham.run/learn/how-much-caffeine-before-a-race) — 3–6 mg per kilogram of body weight, taken about 45–60 minutes before the start, improves endurance performance by roughly 2–4%.
- [How long does caffeine last in your system?](https://ham.run/learn/what-is-caffeine-half-life) — Plasma caffeine peaks about 45 minutes after ingestion and has a half-life of roughly 5 hours, so a pre-race dose is still substantially present at the finish of a marathon.
- [Does daily coffee reduce caffeine's race-day benefit?](https://ham.run/learn/does-caffeine-tolerance-reduce-performance) — Habitual intake above roughly 300 mg per day attenuates the acute ergogenic response by around 30%. Whether a pre-race withdrawal helps is less clear than the folklore suggests.
- [Does caffeine cause stomach problems when running?](https://ham.run/learn/caffeine-and-gi-distress) — High doses, above roughly 400 mg, meaningfully raise the risk of gastrointestinal distress during a race — and running already stresses the gut on its own.
- [Does nicotine improve endurance performance?](https://ham.run/learn/does-nicotine-improve-endurance-performance) — The evidence says mostly no — 12 of 16 studies found no effect. It is highly addictive, and it has been on the WADA monitoring programme since 2012.
- [What is an ergogenic aid?](https://ham.run/learn/what-is-an-ergogenic-aid) — Anything that improves performance — substance, technique or equipment. The category spans well-evidenced interventions like caffeine and carbon-plate shoes and a great deal that does not survive scrutiny.

## Workouts

The workout generator (`/workout`) builds a session from a race-time anchor, a training
phase (base / build / peak), and an optional time budget. Quality doses follow Daniels 2014
windows — interval sessions hold 15–25 min of work, threshold 20–40 min, repetition 5–8 min —
and are prescribed in the time domain, then converted to track-friendly distances at the
athlete's own paces, so a 4:45 marathoner gets 6 × 600 m where a 2:45 marathoner gets
6 × 1000 m. Sessions export to .fit for a Garmin watch.

32 canonical sessions are published at `/workout/library`, each with a full step list.

## Glossary

55 exercise-physiology definitions at `/glossary` — VO₂max, LT1/LT2, cardiac drift,
running economy, RER, glycogen, ACWR, the Banister fitness-fatigue model, the Riegel power-law
model, grade-adjusted pace, and more.

## Other Pages

- `/ai-info` — Model provenance, validated ranges, and stated limitations
- `/pace` — Pace chart for 5K, 10K, half marathon, and marathon
- `/athlete` — Athlete profile: VO₂max, weight, HR zones, marathon PR, .fit import
- `/mcp` — MCP server documentation
- `/about` — About this site
- `/privacy` — Privacy policy (no third-party analytics)

## Resources for Agents

- MCP server: `https://mcp.ham.run/mcp` — the same calculation functions as tools, public and stateless
- Curated link map: `https://ham.run/llms.txt`
- API catalog: `https://ham.run/.well-known/api-catalog` (application/linkset+json)
- Sitemap: `https://ham.run/sitemap.xml`
- Course data index: `https://ham.run/data/courses_index.json`

## Disclaimer

These models are educational tools based on published exercise-physiology research. They
produce estimates, not prescriptions, and they model a population — not you. Individual
physiology varies widely; consult a coach or sports scientist for personalised guidance.
See `/ai-info` for the specific limitations of each model.