Guides
Metric and habit breakdowns with research references — what actually moves sleep, HRV, and recovery.
Active vs Total Calories: What's the Difference
Why your tracker shows two different numbers, which one is your real workload, and how far to trust either. With research on tracker accuracy.
Alcohol and Sleep: How It Hits HRV and Recovery
Why even a couple of evening drinks lower nighttime HRV, raise resting heart rate, and steal deep and REM sleep — and how many hours it takes to recover.
Ashwagandha: effects, side effects and risks, and how to test it on yourself
Meta-analyses on stress, anxiety and sleep, plus documented liver and thyroid risk case reports and a separate Denmark ban — with sourced numbers for every claim.
Best Bedroom Temperature for Sleep
There's no single "correct" number — but controlled studies show heat clearly hurts sleep, while cold works differently. We break down the actual figures from several studies and the wide variation between people.
Blood Oxygen (SpO2) During Sleep: Normal Levels and Meaning
What blood oxygen level is normal during sleep, why it drops, and what the numbers from your ring mean. When low SpO2 hints at apnea — and when it's just an artifact.
Brain Fog — Common Causes and How to Track It
Why brain fog happens — sleep loss, menopause, long COVID, hypothyroidism — and how to check it objectively: a self-rating plus a reaction-time and Stroop test.
Caffeine and Sleep: When to Stop Drinking Coffee
How long caffeine stays in your system, how it steals deep sleep even when you fall asleep fine, and what time to take your last cup. Backed by research.
Chronotype and Bedtime: Night Owl or Early Bird
What chronotype is, why night owls and early birds need different bedtimes, and how to shift your schedule without fighting your body. Grounded in sleep data and research.
Colmi R02 vs Oura Ring: A Personal Comparison of a Cheap Smart Ring
A personal comparison of the budget Colmi R02 smart ring against Oura Ring — what matched, what didn't, and the research context for Oura's own accuracy.
Creatine for the brain: what the meta-analysis found and how to test it on yourself
Searches for "creatine for brain" grew 118% this year. The RCT meta-analysis says: the memory effect is null in young healthy adults, large in older adults. We break down the data and a self-test protocol.
Deep Work and Productive Hours: How Many You Really Get
How RescueTime and similar tools decide what counts as a productive hour, where that count lies, and why your real ceiling is lower than the report says.
How Many Steps a Day Do You Need: The 10,000 Myth
Where the 10,000-step figure came from, what the research actually shows about your real target, and how to build up steps without obsessing. With data and references.
How Much Deep Sleep Do You Need (and How to Get More)
How much deep sleep is normal in hours and percent, why it matters, what reduces it, and how to create the conditions to get more. With research references.
How much HRV changes from night to night
Real data: consecutive nights differ in HRV by 17% on average, and by more than 20% in 44% of cases. Why a single night means nothing and what to look at instead.
How much protein you actually need per day
The RDA is 0.8 g/kg. For muscle gain, the effect plateaus around 1.6 g/kg/day (a meta-analysis of 49 RCTs). A calculator by weight, goal, training and age — plus how to split it across meals.
How Much Sleep Do You Need? Normal Range by Age
How many hours of sleep count as normal for adults, teens, and other ages — per the official AASM/SRS consensus and National Sleep Foundation recommendations. With an age table and source references.
How to Improve Heart Rate Variability (HRV)
What HRV is, why it drops, and which habits actually raise it — sleep, breathing, training, alcohol. No myths, with research references.
Japanese walking: what the study actually showed and how to test it yourself
Search interest in "Japanese walking" is up 2968% year over year. The viral version promises weight loss in weeks — the trial measured strength, VO2peak and blood pressure over 5 months in older adults. What you can actually see in your own data in 4 weeks.
Magnesium for sleep: which form, what the evidence says, how to test it on yourself
Glycinate or L-threonate? A meta-analysis in older adults, one RCT on L-threonate, and the evidence gap nobody talks about — plus a self-test protocol.
Mouth taping for sleep: what the studies actually show
Mouth taping is a popular sleep-hack recommendation. A 2025 systematic review pooled 10 studies in 213 patients — and found both possible benefit and a real asphyxiation risk. Here's what's actually backed by evidence.
Nighttime Body Temperature Deviation: Illness, Ovulation, Overheating
What nighttime temperature deviation shows, what raises it (illness, alcohol, a hot room, ovulation), and why the trend matters more than a single night. With research references.
Readiness Score: What It Is and How to Improve It
Which contributor drags the score down hardest, why it swings on an ordinary day, and whether a low readiness is reason to skip training.
REM Sleep: Normal Amount, Function, and How to Get More
How much REM sleep is normal, what it does (memory, emotion), and which habits actually increase it. What suppresses REM and how it shows up in Oura data.
Resting Heart Rate: Normal Range and How to Lower It
What counts as a normal resting heart rate, what raises it, and which habits genuinely lower it — cardio, sleep, alcohol, caffeine. Grounded in data and research.
Sleep Breathing Disturbances and Apnea: What to Watch
What the breathing disturbance index and nighttime SpO2 actually show, what's normal, when it signals apnea, and what genuinely helps — no panic, no myths.
Sleep Efficiency: What It Is and How to Improve It
The formula on your own numbers, the percentage that counts as good, why 100% never happens, and the habits that actually shift efficiency.
Sleeping Heart Rate: What's Normal and How to Lower It
What a normal sleeping heart rate is, why it rises (alcohol, late meals, stress, illness), and how to lower it. The trend matters more than a single number — with research references.
Sleepmaxxing: which sleep levers actually move your Sleep Score — and how to test them one at a time
Mouth tape, magnesium, 18°C, morning light, no screens — you can't test the whole sleepmaxxing stack at once. We split the levers apart, order them by evidence, and show what 700 nights of one person's data say about a steady schedule.
Stress and Recovery: Reading Your Autonomic Balance
What a daytime "stress ratio" really reflects, why not all stress is harmful, and which signals point to chronic overload — with practical tools and research references.
The Physiological Sigh: Fast Stress Relief Through Breathing
What the physiological sigh is (double inhale + long exhale), why it calms you within seconds, and how to do it right. Backed by research.
Walking After Eating and Blood Sugar: How Many Minutes, and When
Activity after a meal blunts the glucose spike from as little as 1 minute of stair climbing — and the effect grows with duration and depends on how soon after eating you start. We break down the numbers from meta-analyses and controlled trials.
Yoga and HRV: what actually changes in your ring data — and how to check
Search demand for yoga and breathwork is climbing, but the science is mixed: a 2015 review found no convincing evidence, later meta-analyses found a small effect. What this means for your ring readings and how to test it on your own data.