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Readiness scores, HRV, sleep stages, focus streaks. We take the readings apart: what the sensor can actually detect, what the study actually found, and where the number becomes a story someone is selling you.
Almost every HRV-by-age table online traces back to one 1998 study of 24-hour Holter recordings. Your wearable measures something different, overnight, with a different metric.
Peak blood levels arrive around 50 minutes in. Whether anything useful happens at that moment is a separate question, and the answer is narrower than the marketing.
Two drinks is already enough to damage REM sleep. You need about five before alcohol actually helps you fall asleep faster, and by then the second half of the night is wrecked.
Dark mode is the most popular eye-care intervention nobody tested first. Four decades of legibility research point the other way, and the reason is your pupil.
The research on interruption does not say what productivity blogs say it does. Interrupted work gets finished faster. The cost lands somewhere else entirely.
Most answers give a number and stop there. That number is the half-life. Meaning half the dose is still in you when it elapses, which is a very different fact.
The measured American shower runs 7.8 minutes at 2.1 gallons a minute, about 16 gallons in all. That is a known number. What most people miss is that heating those gallons costs several times more than the gallons themselves, which changes which fix is worth making.
The term is borrowed from bond finance, where an issuer pays into a fund on a schedule so a known debt can be met. The household version does the same for car repairs, insurance premiums and December. The arithmetic is trivial; the evidence is about why labelling the money changes what happens to it.
A HEPA purifier sized to the room reliably cuts fine particles by half or more, and the trials that measured blood vessels and airways found real effects. Odours, gases, viruses in a shared room, and the ioniser on the front panel are a different story.
Your body clock does not respond to willpower or to going to bed early. It responds to light, and specifically to when the light arrives.
Of all the numbers a wearable shows you, this is the one with the strongest link to how long you live, and the one most people ignore in favour of step counts.
A £200 million category rests on a claim that the highest tier of medical evidence review could not find support for. Here is what the lenses do, and what actually helps tired eyes.
Movement, recovery, and what the sensors on your wrist can really see.
PublishedAttention, memory, mood, and the practices claimed to improve them.
PublishedTrackers, stages, routines, and the gap between the two.
PublishedDevices, apps and AI tools, tested rather than summarised from press releases.
PublishedFocus, remote work, burnout, and the productivity industry around them.
PublishedNutrition claims traced back to the studies underneath them.
PublishedLiving with less, and which sustainable choices actually add up.
PublishedConscious spending, subscription creep, and the cost of optimising yourself.
PublishedLight, air, noise, and the physical space you spend most of your life in.
PublishedMoving through the world without leaving your nervous system behind.
PublishedAgeing, fitness markers, and which interventions have evidence behind them.
PublishedDevices and tools we have actually used, for long enough to have an opinion.
PublishedOne email each Thursday: what we tested, which claim collapsed under a closer look, and the one number worth paying attention to this week.
