{"query": "A thirty-year-old's maximum heart rate", "count": 2, "results": [{"id": "card_works_heart_rate", "title": "A thirty-year-old's maximum heart rate", "shelf": "the-works", "surface": "secular", "snippet": "The Tanaka formula estimates maximum heart rate as 208 − 0.7·age — 187 bpm at thirty, the modern refinement of the old 220 − age rule.  Worked & sealed by the engine — HRmax = 208 − 0.7·30 = 187 bpm. ", "authority_tier": "verified", "source": "The Works — worked & sealed", "generated": false}, {"id": "card_src_pron_old_s", "title": "old's", "shelf": "pronunciation", "surface": "secular", "snippet": "", "authority_tier": "", "source": "", "generated": false}]}