{"success":true,"version":"v1","request":{"tool":"list_calculators","category":"fitness"},"result":{"entity_type":"calculator_list","status":"completed","count":8,"calculators":[{"calculator_id":"running-pace","entity_type":"calculator","name":"Running Pace Calculator","category":"fitness","tool_name":"calculate_running_pace","description":"Computes running pace in min/km and min/mile and speed in km/h and mph from a distance and elapsed time, and projects the finish time for 5 km, 10 km, half marathon and marathon at that constant pace.","use_when":"You know a distance and the time it took (or a target time) and need the pace, the equivalent speed, or the time that pace gives over standard race distances.","do_not_use_when":"You want a realistic prediction of a longer race from a shorter one (pace slows with distance; use race-time-predictor), or you only need to convert between pace and speed units (use pace-converter).","required_inputs":["distance","time"],"optional_inputs":["distance_unit"],"urls":{"html":"https://tttkmbb.com/fitness/running-pace","markdown":"https://tttkmbb.com/fitness/running-pace.md","schema":"https://tttkmbb.com/api/v1/calculators/running-pace","api":"https://tttkmbb.com/api/v1/calculate/running-pace"}},{"calculator_id":"race-time-predictor","entity_type":"calculator","name":"Race Time Predictor","category":"fitness","tool_name":"predict_race_time","description":"Predicts finish times for 5 km, 10 km, half marathon and marathon from one known race result using Riegel's endurance formula T2 = T1 × (D2/D1)^1.06, with the corresponding paces.","use_when":"You have a recent race time (or time trial) and want equivalent-effort predictions for other standard distances, e.g. to set a marathon goal from a half-marathon result.","do_not_use_when":"You only need the pace or constant-pace splits of a run (use running-pace), the known effort was a trail or very hilly race, or it was shorter than about 1.5 km or longer than a marathon.","required_inputs":["distance","time"],"optional_inputs":["distance_unit","exponent"],"urls":{"html":"https://tttkmbb.com/fitness/race-time-predictor","markdown":"https://tttkmbb.com/fitness/race-time-predictor.md","schema":"https://tttkmbb.com/api/v1/calculators/race-time-predictor","api":"https://tttkmbb.com/api/v1/calculate/race-time-predictor"}},{"calculator_id":"calories-burned","entity_type":"calculator","name":"Calories Burned Calculator","category":"fitness","tool_name":"estimate_calories_burned","description":"Estimates the calories burned during an activity from body weight, duration and the activity's MET value from the 2011 Compendium of Physical Activities, using the ACSM metabolic equation kcal/min = MET × 3.5 × kg / 200.","use_when":"You need an estimate of energy expenditure for a workout, sport or chore of known duration for a person of known weight.","do_not_use_when":"You need total daily calorie needs (use tdee) or resting expenditure (use bmr); MET values are population averages and ignore fitness level, terrain and intensity within a category.","required_inputs":["weight_kg","duration_minutes","activity"],"optional_inputs":[],"urls":{"html":"https://tttkmbb.com/fitness/calories-burned","markdown":"https://tttkmbb.com/fitness/calories-burned.md","schema":"https://tttkmbb.com/api/v1/calculators/calories-burned","api":"https://tttkmbb.com/api/v1/calculate/calories-burned"}},{"calculator_id":"one-rep-max","entity_type":"calculator","name":"One-Rep Max Calculator","category":"fitness","tool_name":"estimate_one_rep_max","description":"Estimates the one-repetition maximum from a weight lifted for 2–12 repetitions using the Epley, Brzycki and Lombardi equations, reports their average, and lists training loads at 95 % to 70 % of that 1RM.","use_when":"You want to estimate maximal strength or program training percentages without attempting a true single-rep maximum.","do_not_use_when":"The set was more than 12 repetitions (prediction error grows quickly) or was not taken close to failure; use a heavier, lower-rep set instead.","required_inputs":["weight_lifted","reps"],"optional_inputs":[],"urls":{"html":"https://tttkmbb.com/fitness/one-rep-max","markdown":"https://tttkmbb.com/fitness/one-rep-max.md","schema":"https://tttkmbb.com/api/v1/calculators/one-rep-max","api":"https://tttkmbb.com/api/v1/calculate/one-rep-max"}},{"calculator_id":"vo2-max","entity_type":"calculator","name":"VO2 Max Calculator","category":"fitness","tool_name":"estimate_vo2_max","description":"Estimates maximal oxygen uptake (VO2max, ml/kg/min) from the distance covered in the Cooper 12-minute run test, and/or from the ratio of maximum to resting heart rate (Uth et al. 2004).","use_when":"You have a 12-minute run distance or resting and maximum heart rates and want a field estimate of aerobic fitness.","do_not_use_when":"A laboratory or wearable-measured VO2max is available, or the person cannot run continuously for 12 minutes; the heart-rate method also requires a true (measured) maximum heart rate.","required_inputs":[],"optional_inputs":["distance_m","resting_heart_rate","max_heart_rate"],"urls":{"html":"https://tttkmbb.com/fitness/vo2-max","markdown":"https://tttkmbb.com/fitness/vo2-max.md","schema":"https://tttkmbb.com/api/v1/calculators/vo2-max","api":"https://tttkmbb.com/api/v1/calculate/vo2-max"}},{"calculator_id":"steps-to-distance","entity_type":"calculator","name":"Steps to Distance Calculator","category":"fitness","tool_name":"convert_steps_to_distance","description":"Converts a pedometer step count into distance using a measured stride length, or a walking stride estimated from height (stride ≈ 0.414 × height).","use_when":"You have a daily step count and want to know the distance walked in kilometres and miles, or the number of steps in a kilometre or mile.","do_not_use_when":"The steps were mostly running (running strides are considerably longer; 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