{
  "calculator": "heart-rate-zone-calculator",
  "title": "Heart Rate Zone Calculator",
  "site": "AI Fit Hub",
  "input": {},
  "defaults_used": {
    "age": 30,
    "resting_hr": 60,
    "method": "karvonen",
    "max_hr_formula": "fox",
    "max_hr": 0
  },
  "result": {
    "maxHr": 190,
    "hrr": 130,
    "zones": [
      {
        "zone": "Zone 1 (Recovery)",
        "lowBpm": 125,
        "highBpm": 138
      },
      {
        "zone": "Zone 2 (Endurance)",
        "lowBpm": 138,
        "highBpm": 151
      },
      {
        "zone": "Zone 3 (Tempo)",
        "lowBpm": 151,
        "highBpm": 164
      },
      {
        "zone": "Zone 4 (Threshold)",
        "lowBpm": 164,
        "highBpm": 177
      },
      {
        "zone": "Zone 5 (VO2 Max)",
        "lowBpm": 177,
        "highBpm": 190
      }
    ],
    "method": "karvonen",
    "maxHrSource": "220 − age",
    "warnings": []
  },
  "provenance": {
    "run": "https://aifithub.io/api/run/heart-rate-zone-calculator",
    "page": "https://aifithub.io/heart-rate-zone-calculator/",
    "methodology": "https://aifithub.io/methodology/heart-rate-zone-calculator/",
    "contract": "https://aifithub.io/contracts/heart-rate-zone-calculator.json",
    "engine": "https://aifithub.io/engines/heart-rate-zone-calculator.js",
    "engine_sha256": "734c2ac144a4ae92a7284a23b02d591c1de0cd52efbb13bc81ce74aec85eb386",
    "build": "9e8a56a16bda662ba90601b49561a2b176e9c379"
  },
  "disclaimer": "General fitness estimates — not medical advice.",
  "license": "https://creativecommons.org/licenses/by/4.0/",
  "cite": "AI Fit Hub, Heart Rate Zone Calculator (engine 734c2ac144a4), https://aifithub.io/api/run/heart-rate-zone-calculator"
}