{
  "address": "a29afdfec7c24a0c283c5106f2bae9cb",
  "category": "other",
  "question": "What are the target heart rate zones for a 40-year-old with a resting heart rate of 65 bpm?",
  "answer": "HRmax 180 bpm; percent-of-max zone 90-153 bpm; Karvonen zone 123-163 bpm",
  "askedBy": {
    "kind": "guest",
    "display": "method deck",
    "stamped": false,
    "id": null
  },
  "answeredBy": "method",
  "madeAt": "2026-09-30T22:39:30.722Z",
  "validUntil": null,
  "validityClass": "forever",
  "sources": [
    {
      "label": "Origin of the 220-minus-age maximum heart rate estimate",
      "url": null
    },
    {
      "label": "Target Heart Rates Chart",
      "url": "https://www.heart.org/en/healthy-living/exercise-and-physical-activity/fitness-basics/target-heart-rates"
    }
  ],
  "supersedes": null,
  "supersededBy": null,
  "isSeed": false,
  "seedSource": null,
  "seedAttribution": null,
  "duplicateOfQid": null,
  "publishedAt": null,
  "unpublishedAt": null,
  "voteCount": 0,
  "queuedForSubstrate": false,
  "answerMethod": "method",
  "unsourced": false,
  "source": {
    "kind": "edition_page",
    "value": "Fox SM, Naughton JP, Haskell WL. Physical activity and the prevention of coronary heart disease. Ann Clin Res. 1971;3(6):404-432.",
    "retrieved_utc": "2026-09-30T19:35:00Z"
  },
  "qsha256": "c657f3031e0afb71c8630ccb0968dc47b703d8af06b805a042494fe507f2397b",
  "runOne": null,
  "cardContractVersion": "card_contract/1",
  "deck_id": "method-deck",
  "deck_title": "Method Deck",
  "method": {
    "name": "Target heart rate zones",
    "version": "1",
    "source_url_or_file": "methods/target-heart-rate-zones.cjs",
    "sha256_of_method_file": "0a0cc5f290c9d18697d25cbf08b6662e2b6250936c970d739140e4d92e3cd029"
  },
  "receipt": {
    "inSubstrate": false,
    "local": true,
    "modelCallsAtMint": 0,
    "tokensAtMint": 0
  },
  "method_deck": {
    "inputs": [
      {
        "name": "age_years",
        "type": "number",
        "unit": "years",
        "required": true,
        "description": "Age in years",
        "min": 0
      },
      {
        "name": "resting_hr",
        "type": "number",
        "unit": "bpm",
        "required": false,
        "description": "Resting heart rate, enables the Karvonen method",
        "min": 0
      }
    ],
    "outputs": [
      {
        "name": "hr_max",
        "unit": "bpm",
        "description": "Estimated maximum heart rate (220 minus age)"
      },
      {
        "name": "pctmax_low",
        "unit": "bpm",
        "description": "Lower bound of the percentage-of-max zone (50%)"
      },
      {
        "name": "pctmax_high",
        "unit": "bpm",
        "description": "Upper bound of the percentage-of-max zone (85%)"
      },
      {
        "name": "karvonen_low",
        "unit": "bpm",
        "description": "Lower bound of the Karvonen zone (50% of heart rate reserve), only when resting_hr given"
      },
      {
        "name": "karvonen_high",
        "unit": "bpm",
        "description": "Upper bound of the Karvonen zone (85% of heart rate reserve), only when resting_hr given"
      }
    ],
    "steps": [
      "hr_max = 220 - age_years.",
      "Percentage-of-max method: pctmax_low = 0.50 * hr_max, pctmax_high = 0.85 * hr_max.",
      "If resting_hr is given, Karvonen method: heart_rate_reserve = hr_max - resting_hr; karvonen_low = resting_hr + 0.50 * heart_rate_reserve; karvonen_high = resting_hr + 0.85 * heart_rate_reserve.",
      "Round every bpm value to the nearest whole number."
    ],
    "constants": [
      {
        "name": "age_coefficient_hrmax",
        "value": 220,
        "unit": "bpm",
        "source": 0
      },
      {
        "name": "moderate_low_pct",
        "value": 0.5,
        "unit": "fraction",
        "source": 1
      },
      {
        "name": "vigorous_high_pct",
        "value": 0.85,
        "unit": "fraction",
        "source": 1
      }
    ],
    "examples": [
      {
        "name": "worked example",
        "inputs": {
          "age_years": 40,
          "resting_hr": 65
        },
        "expected": {
          "answer": "HRmax 180 bpm; percent-of-max zone 90-153 bpm; Karvonen zone 123-163 bpm"
        },
        "check": "hr_max = 220-40 = 180. pctmax: 0.5*180=90, 0.85*180=153. HRR = 180-65=115. Karvonen low = 65+0.5*115=65+57.5=122.5, JS Math.round rounds half up to 123. Karvonen high = 65+0.85*115=65+97.75=162.75 rounds to 163."
      },
      {
        "name": "test vector: no resting heart rate",
        "inputs": {
          "age_years": 25
        },
        "expected": {
          "answer": "HRmax 195 bpm; percent-of-max zone 98-166 bpm"
        },
        "check": "hr_max = 220-25=195. 0.5*195=97.5 rounds to 98. 0.85*195=165.75 rounds to 166."
      }
    ],
    "disclaimer": "General formula only. Not medical advice. Dosing decisions belong to a licensed clinician and the product's label.",
    "deck_category": "health"
  },
  "status": "minted",
  "kind": "method",
  "provenanceClass": "own_question",
  "provenance": {
    "schema": "card_provenance/2.0.0",
    "chain": [
      {
        "source": {
          "kind": "edition_page",
          "value": "Fox SM, Naughton JP, Haskell WL. Physical activity and the prevention of coronary heart disease. Ann Clin Res. 1971;3(6):404-432.",
          "retrieved_utc": "2026-09-30T19:35:00Z"
        },
        "sha256": "1d57b99f9558de84ca30220df63373ab89e2453da3782d0e4c84c2634d3dc568",
        "supersedes": null,
        "added_utc": "2026-09-30T22:39:30.722Z",
        "added_by": "method:Target heart rate zones",
        "why": "the method that computed this answer",
        "check": null,
        "status_label": "pending",
        "signature": null
      }
    ]
  }
}