Learn
Understand your health data
Plain-English explainers for the numbers your devices track, written by the coaches who read them.
Getting started
Heart and cardio
Guide
What Is HRV?Heart rate variability explained, what a good number is, and how to raise it.
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VO2 Max ExplainedWhat a good score is by age and how to improve it.
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Zone 2 Heart RateHow to find and train your real aerobic base pace.
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Active Zone MinutesHow many you need per day and why minutes in zone beat steps.
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Resting Heart RateWhat a good resting heart rate is by age and fitness, and what moves it.
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Max Heart RateHow to calculate it and why 220 minus age is only a rough estimate.
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Heart Rate RecoveryHow fast your heart rate drops after exercise, and what it says about fitness.
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Heart Rate Zones During ExerciseHeart-rate zones turn a changing pulse into useful intensity bands. They help separate easy aerobic work from moderate, threshold, and very hard efforts, but the exact boundaries depend on the method and the person.
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Running Heart Rate: Target ZonesRunning heart rate only makes sense relative to your own maximum or threshold, the purpose of the run, and the conditions. An easy run should not have the same heart-rate profile as a tempo session, hill workout, or race.
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Running Cadence: What Is a Good SPM?Cadence is how many steps you take per minute while running. It changes naturally with pace, body size, terrain, grade, fatigue, and running style, so the useful number is usually your own cadence at a comparable pace rather than a universal target.
Guide
Cycling Heart Rate Zones ExplainedCycling heart-rate zones help organize easy endurance, tempo, threshold, and harder efforts, but your cycling heart rate may not match your running heart rate at the same perceived effort.
Strength and training
Sleep and recovery
Guide
Caffeine Before BedHalf-life, how long caffeine stays in your system, and a practical bedtime cutoff.
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Sleep DebtWhat it is, how it builds, and how to recover it.
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Menstrual Cycle PhasesThe four phases and how to read training, recovery, and nutrition by phase. Calendar-based, not medical.
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Sleep StagesDeep, REM, and light explained, and how much deep and REM you actually need.
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Readiness ScoreWhat a readiness or recovery score is, and how Oura and Whoop compute it.
Nutrition and body
Guide
How Much Caffeine Is Too Much?The 400 mg daily benchmark, when a lower limit makes sense, and how to track your real total.
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How Much Water Should I Drink?Daily water intake benchmarks, what counts toward them, and what water calculators miss.
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TDEE CalculatorEstimate your daily energy burn, plus how we compute your real one.
Guide
Macros for RecompositionProtein and calories to lose fat and build muscle at once.
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Protein IntakeHow much protein per day by bodyweight and goal.
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Calorie DeficitWhat a calorie deficit is and a safe rate to lose fat.
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How to Measure Your Waist CorrectlyUse the midpoint between your lowest rib and the top of your hip bone, then keep the tape level all the way around.
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Body Fat PercentageWhat a healthy body fat percentage is by age and sex.
Calories and energy
Explainer
What Is TDEEWhat total daily energy expenditure is made of, and why yours keeps moving.
Explainer
Maintenance CaloriesThree ways to estimate the intake that matches what you burn.
Explainer
Calories Burned AccuracyWhat a watch can and cannot tell you about your calorie burn.
Explainer
Calories In, Calories OutThe energy balance equation, and why the scale ignores it daily.
Healthspan and longevity
Guide
What Is Healthspan?Healthspan versus lifespan, and what the term actually means.
Guide
How to Improve HealthspanThe fitness, movement, sleep, body, glucose, and lab inputs you can act on.
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What Is Cardio Age?What the age-shaped fitness estimate means and how calculations differ.
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How to Improve Cardio AgeImprove the fitness underneath the number instead of gaming the score.
Guide
How Much Sitting Is Too Much?Why there is no universal sitting cutoff and what to do instead.
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How Often Should You Get Up?A practical way to break up long desk-heavy days.
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Biomarker TrackingThe lab values that matter for longevity, tracked over time.
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