# HAM.RUN — open physiology calculators for endurance running > HAM.RUN is a free, open-source performance lab for marathon runners: 10 interactive physiology models, elevation profiles and grade-adjusted pacing for 32 marathon courses, and 61 explainers on the underlying exercise science. Every model is implemented from published research with the source cited in the code, every calculation runs client-side in the browser, and nothing about a user's training is uploaded unless they opt in. The same calculation functions are exposed as tools over a public MCP server, so an assistant can call the models directly instead of approximating them. ## Calculators - [Running Economy Calculator](https://ham.run/economy): Running economy (RE) measures the oxygen cost of running at a given speed — typically expressed in mL O₂/kg/km. - [Marathon Periodization Planner](https://ham.run/periodization): Marathon periodization is the systematic planning of training intensity distribution across a training block. - [Training Adaptation Map](https://ham.run/adapt): Not all training sessions carry the same risk-to-reward ratio. - [HR Pacing Simulator](https://ham.run/hr): Cardiac drift is the gradual rise in heart rate that occurs during prolonged exercise at a constant pace. - [Substrate & Tlim Calculator](https://ham.run/substrate): During running, your body burns a mix of carbohydrates and fat for fuel. - [Caffeine & Stimulants Simulator](https://ham.run/ergogenic): Caffeine is the most widely studied legal ergogenic aid in endurance sports. - [Sauna Heat Adaptation Simulator](https://ham.run/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. - [Race Time Predictor](https://ham.run/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. - [Marathon Training Plan Generator](https://ham.run/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. - [Running Workout Generator](https://ham.run/workout): Turning up at the track without a session in mind is the most common way quality training dies. ## Reference - [Pace Chart](https://ham.run/pace): Per-kilometre and per-mile split tables for 5K, 10K, half marathon, and marathon at any finish time. - [Glossary](https://ham.run/glossary): 55 exercise-physiology definitions — VO₂max, LT1/LT2, cardiac drift, ACWR, RER, TSB, grade-adjusted pace. - [Learn](https://ham.run/learn): 61 concept explainers, each ending in the live calculator for that concept. - [Model provenance and limitations](https://ham.run/ai-info): Which published model backs each calculator, its validated range, and where it breaks down. Written to be quoted. ## Marathon courses - [Course index](https://ham.run/marathon): Elevation profiles, difficulty ratings, and grade-adjusted split tables for 32 marathons, including all 7 World Marathon Majors. - [The Flattest Marathon Courses](https://ham.run/marathon/rankings/flattest-marathons): Courses ranked by total elevation gain, least first. - [The Hilliest Marathon Courses](https://ham.run/marathon/rankings/hilliest-marathons): Courses ranked by total elevation gain, most first. - [Net-Downhill Marathon Courses](https://ham.run/marathon/rankings/net-downhill-marathons): Courses ranked by net elevation change, biggest drop first. - [Marathons With the Hardest Finish](https://ham.run/marathon/rankings/hardest-marathon-finishes): Courses whose toughest stretch lands after 30 km, ranked by how hard it bites. - [World Marathon Majors: Course Profiles Compared](https://ham.run/marathon/rankings/world-marathon-majors): Every Major course, ranked flattest to hilliest. - [The Biggest Marathons by Field Size](https://ham.run/marathon/rankings/biggest-marathons): Courses ranked by the number of runners on the start line. - [Goal-time pacing pages](https://ham.run/marathon/boston/pace/4-00-00): Every course carries grade-adjusted split tables for 13 goal times from 2:30 to 6:00, at /marathon/{slug}/pace/{time}. ## Concepts - [Fuelling and substrate](https://ham.run/learn): 9 explainers — What is glycogen, and why does it run out?, How many carbs per hour should you take in a marathon?, What is the SGLT1 limit on carbohydrate absorption?, Why do sports drinks mix glucose and fructose?, … - [Intensity and thresholds](https://ham.run/learn): 10 explainers — What is lactate threshold?, LT1 vs LT2: what is the difference?, What is VO₂max?, What is a good VO₂max for a runner?, … - [Training load and recovery](https://ham.run/learn): 10 explainers — What is ACWR (acute:chronic workload ratio)?, What are CTL, ATL and TSB?, What is training stress score (TSS)?, What is the Banister fitness-fatigue model?, … - [Heart rate, heat and hydration](https://ham.run/learn): 9 explainers — What is cardiac drift?, What is aerobic decoupling, and what is a good value?, What is heart rate reserve (HRR)?, How do you calculate running heart rate zones?, … - [Running economy and biomechanics](https://ham.run/learn): 8 explainers — What is running economy?, What is a good running economy?, Do carbon-plate shoes actually make you faster?, What is the ideal running cadence?, … - [Racing, pacing and terrain](https://ham.run/learn): 9 explainers — What is grade-adjusted pace (GAP)?, What is the Minetti gradient cost model?, What is the Riegel formula for race prediction?, How do you predict your marathon time?, … - [Caffeine and ergogenic aids](https://ham.run/learn): 6 explainers — How much caffeine should you take before a race?, How long does caffeine last in your system?, Does daily coffee reduce caffeine's race-day benefit?, Does caffeine cause stomach problems when running?, … ## Workouts - [Workout generator](https://ham.run/workout): Builds a session from a race-time anchor, training phase, and time budget; doses follow Daniels 2014 quality windows and are prescribed in the time domain, then converted to distances at the athlete's own paces. - [Workout library](https://ham.run/workout/library): 32 canonical sessions with full step lists, exportable to .fit for a Garmin watch. ## For agents - [MCP server](https://ham.run/mcp): Public, anonymous, stateless Model Context Protocol endpoint at https://mcp.ham.run/mcp exposing the same calculation functions the website uses. - [Markdown summary](https://ham.run/index.md): This site as one markdown document. Also served from / under `Accept: text/markdown`. - [Sitemap](https://ham.run/sitemap.xml): Every indexable URL with last-modified dates. - [Course data](https://ham.run/data/courses_index.json): Machine-readable course index; per-course detail at /data/courses/{slug}.json. ## Optional - [About](https://ham.run/about): What the site is, who it is for, and how the models were chosen. - [Privacy](https://ham.run/privacy): No third-party analytics or ad trackers; calculations are client-side. - [Terms](https://ham.run/terms): Educational use; the models are estimates, not medical or coaching prescription.