Blog
Why am I so tired after working out? Sleep, HRV and what three studies show
Why am I so tired after working out when the same session felt easy last week? What studies say about sleep loss, heart rate variability and why one morning number is not a verdict.
Sedentary lifestyle: what the WHO guidelines and accelerometer data say
What counts as a sedentary lifestyle by WHO numbers, why there is no hours-per-day limit for sitting, and what 36,383 people wearing accelerometers showed about activity and mortality.
Best temperature for sleep: what research says about bedroom heat, cold and AC at night
Best temperature for sleep: the studies give no single bedroom number. What they say about bedding, humid heat, sleeping with AC on all night and cold rooms in winter.
What affects immunity: what research shows and what is marketing
What affects immunity, according to the studies: sleep, stress, social ties, age, vitamin C and echinacea, and why "boost your immunity" is the wrong frame. Evidence and limits for each.
Sleep and catching a cold: what the virus-challenge studies show
Healthy volunteers were given a cold virus on purpose; those who had slept less beforehand fell ill more often. What the studies measured, how uncertain the numbers are, what they did not test.
Weather and sleep: heat, daylight, and pressure — what the evidence actually shows
Heat and a stuffy bedroom, daylight and your body clock, and barometric pressure: three ways weather might touch your sleep — and, honestly, only two of them hold up under evidence.
Sleep debt: how to actually think about it
Where 'sleep debt' comes from, what chronic sleep restriction research shows, why weekend catch-up sleep falls short, and why your own trend and regularity matter more than an hours-based number.
Wrist temperature during sleep: what Apple Watch is actually tracking
Apple Watch reports a nightly wrist-temperature deviation from your own baseline, not your body temperature. What that signal reflects — cycle, sleep, feeling unwell — and what it doesn't.