The most cardiovascular-fitness-correlated daily metric — lower typically indicates better trained aerobic capacity.
Resting heart rate (RHR) is the number of times your heart beats per minute at rest. It's inversely correlated with aerobic fitness — endurance training lowers it over months to years. RHR in the 50s and low 60s is common in well-trained individuals. RHR persistently over 70 warrants attention, and over 80 is meaningfully elevated.
Like HRV, the individual trend matters more than absolute values. A 5–10 bpm rise from your personal baseline for multiple days is a reliable signal for something wrong — most commonly illness incubation, overtraining, acute stress, or alcohol the prior evening.
Oura and Apple Watch both deliver reliable RHR during sleep. Fitness bands like Fitbit and Garmin also work. Manual measurement first thing in the morning (before standing up) is a free option.
RHR is influenced by: aerobic fitness level (primary driver — lower = better-trained), acute illness (rises 5–15 bpm), sleep debt, alcohol, caffeine, stress hormones, hydration status, and pharmacologic agents — beta-blockers lower it; stimulants raise it. Pregnancy and thyroid dysfunction also shift RHR.
On GH peptides, RHR sometimes rises slightly (2–5 bpm) as metabolic rate increases — not concerning. On GLP-1s, RHR typically drops as weight and insulin resistance improve. On retatrutide specifically, a 4–6 bpm RHR elevation has been observed in trials and warrants monitoring in cardiovascular patients. Acute RHR spikes of 10+ bpm from baseline usually signal illness.
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Start tracking →Informational only — not medical advice. Reference ranges vary by lab and individual context. Work with a licensed provider to interpret your specific results.