American biohacker Bryan Johnson claims lowering resting heart rate (RHR) is the most effective health practice, suggesting strategies like reducing caffeine, eating early, avoiding screens before bed, and managing stress. A low RHR, typically 40-60 bpm for athletes and 60-100 bpm for normal adults, indicates better cardiovascular fitness. Doctors note RHR depends on age, fitness, and stress, with rates below 60 bpm potentially indicating bradycardia unless the person is an athlete.