HRV
Heart rate variability, resting heart rate and what those numbers say about regulation.
9 posts
Gearstack Journal
Understand what your numbers say
Practical writing on HRV, sleep, recovery and training. Written for people who want to make sense of their Apple Watch data instead of only collecting it.
Today's edition
29 August 2026
5 new perspectives for making better decisions with your health data.
Training
Winter fitness testing: how football clubs measure progress without a lab
Which fitness tests actually carry meaning in winter preparation, how resting heart rate, HRV and running efficiency show progress over weeks and how a club turns them into one athletic score.
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Community
Parent meetings with data
How youth coaches prepare parent meetings, why documented development defuses the argument about playing time and which data belongs in the conversation.
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HRV in football
How heart rate variability is used in football, why the trend against the personal baseline is what counts, which measurement mistakes happen and how a team uses the values in practice.
Read the postEveryday
Sports watch calories
Studies show errors of 30 percent and more in sports watch energy expenditure while heart rate measurement performs well. What the calorie number is still good for, and what definitely not.
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Documenting development
Which data actually proves a football player’s development, how much documentation is realistic in club life and how notes become a development story per player.
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Understand more. Decide better.
Every earlier article, now in the new image-led G‑Stack design.
Everyday
Understanding sports watch values: the five numbers that count, and the ones you can ignore
Resting heart rate, sleep, HRV, load: which sports watch values actually say something, which are mostly show, and why the first two weeks are only for wearing.
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Day-to-day readiness in football: how coaches judge it before writing the line-up
Why the warm-up impression comes too late, which morning values reveal a player’s readiness and how a squad overview supports the line-up on matchday.
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A team dashboard for football clubs: what it must show so coaches actually use it
Professional clubs have long managed training through data. What a team dashboard needs to show for amateur and youth clubs, why three inputs are enough and where these systems fail in daily use.
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Recording training load: how far the spreadsheet carries and where the dashboard begins
Load management with Excel: what a good spreadsheet needs, the three places where it tears in club life and when switching to a team dashboard pays off.
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Managing training load in youth football: the simple method without devices
How youth coaches measure training load with one number per session, why rapid load spikes are the real risk and what a weekly overview looks like in a team dashboard.
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Training management in a football club: methods that work without a sports scientist
What training management means, which methods have proven themselves in amateur football (session RPE, weekly load, ACWR, readiness) and how a club starts without a lab.
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The watch shows poor recovery, you feel great: whom to believe?
Why sports watch and body feeling diverge on recovery, which measurement errors may be behind it and the simple rule for combining both signals.
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Youth football injuries are rising: the reasons, and what actually protects players
Why sports injuries in children and adolescents have been increasing for years, the role of growth, early specialisation, load spikes and sleep, and what clubs and parents can do about it.
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Calculating maximum heart rate: why 220 minus age misses
Where the 220 minus age rule came from, how far it deviates, which alternative is more accurate, and how to find your real value.
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Resting heart rate: what is normal and what it reveals
Which resting heart rate counts as normal in adults, why a low value is not automatically good, and when a rise actually means something.
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How much sleep do I actually need?
What sleep duration is recommended for adults, why your own need may legitimately differ, and how to find it without a lab.
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Exercise after a cold: when you can start again
The neck check as a simple decision aid, why fever is a hard line, and what a sensible return after an infection looks like.
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How much water a day? What the two litres really mean
Where the common guideline figures come from, why food counts, and the more reliable sign that you had enough.
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HRV by age: what your number actually tells you
The HRV ranges that show up in studies of healthy adults, how strongly age shifts them, and why your own baseline beats any chart.
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Waking at three in the morning: why it is normal
Why brief waking between sleep cycles is ordinary physiology, when it tips into a disorder, and what actually helps in the moment.
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How long does recovery after strength training take?
Why the same muscle group needs anywhere from one to four days, what soreness really tells you, and how to recognise that recovery is done.
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Not enough REM sleep: when the number is a problem
How much REM sleep is typical in adults, why a low reading is usually harmless, and the four things that reliably cut it short.
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How many steps a day actually make sense?
Where the 10,000 really came from, what large analyses show as the useful range, and why the number adds up more easily in company.
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Alcohol and HRV: what an evening drink does to your night
Why HRV drops and heart rate rises after alcohol, how strongly dose matters, and how to observe your own response cleanly.
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Power naps: how short sleep works without wrecking your night
What research says about ideal nap length, why 30 minutes often backfires, and when napping starts to threaten your night sleep.
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The deload week: training less on purpose to keep progressing
Why a reduced training week is not a lost week, what studies say about losing muscle and strength, and how to structure a deload in practice.
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Sleeping through heat: what warm nights do to your recovery
Why sleep suffers at high temperatures, what sensor and wearable studies show, and which ways of cooling down actually help.
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Training partners: why you last longer in a team than alone
The Köhler effect explains why people train markedly longer with a partner, which conditions it needs, and how to put it to work for you.
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Caffeine and HRV: does coffee distort your morning reading?
When coffee can influence an HRV reading, why the direction is not predictable, and how to keep measurements comparable.
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Catching up on sleep at the weekend: helpful, but not a complete reset
What longer weekend sleep can restore, what may remain, and how to recover without creating a large schedule shift.
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Zone 2 without a lab test: finding a useful working range
Why Zone 2 is not one universal heart-rate number, and how the talk test, perceived effort and repeatable sessions can define a useful field range.
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Understanding smartwatch stress data: a signal, not a diagnosis
What a stress score built from heart rate and HRV can show, what it misses, and how to examine patterns without overrating one reading.
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Streaks without pressure: why a rest day should not break your run
A useful fitness streak rewards meaningful consistency rather than daily intensity. Here is how rest, motivation, and personal goals can belong to one routine.
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Low HRV, but you feel good: which signal should you follow?
What to do when HRV and how you feel do not match, without turning one morning reading into an order for the day.
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Seven nights, one rhythm: an experiment in sleep consistency
A practical seven-night experiment for observing your sleep rhythm without trying to optimise every sleep stage.
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Push, Balance or Easy: three better choices than “train or skip”
Turn readiness, how you feel and the goal of a session into a graduated choice instead of reading one score as permission or prohibition.
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Exercise snacks: how short movement sessions fit real life
Short movement sessions can lower the barrier to starting. What exercise-snack research shows, where its limits sit, and how to plan them sensibly.
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Fair fitness challenges: reward progress, not absolute records
Why one shared step target is rarely fair, and how personal baselines, recovery, and social rules can turn a challenge into useful motivation.
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Why HRV changes from night to night, and when that matters
How much your nightly HRV is expected to move, what drives the swings, and the point where a deviation actually means something.
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Understanding HRV: what heart rate variability says about recovery
What heart rate variability actually measures, why there is no normal value, and how to read your own trend without overreacting to it.
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What an AI health coach can do, and where it stops
Where an AI coach with access to your data genuinely helps, what it necessarily fails at, and how to get useful answers out of it.
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Night shifts: what recovery data says about your rhythm
Why HRV and resting heart rate look different on rotating shifts, where the measurement hits its limits, and how to read your trend anyway.
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Readiness instead of guesswork: how a readiness score is built
What goes into a daily readiness value, why the weighting is harder than it looks, and the situations where the score is simply wrong.
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Resting heart rate, HRV and sleep: what actually connects
Why resting heart rate and HRV do not measure the same thing, what it means when they diverge, and which combinations are worth acting on.
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Shift work and sleep: routines that survive a rotating schedule
Why shift work breaks the rhythm, which lever actually works, and which routines hold up when the roster keeps changing.
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Sleep quality beats sleep duration
Why eight hours is not a target, what sleep quality actually means, and which lever gives you the most in daily life.
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How much deep sleep is normal? Context instead of targets
What share of deep sleep is typical, why wearables can only estimate it, and what reliably reduces it.
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Training by readiness: when load actually makes sense
How to adapt a training plan to your recovery values without skipping a session every time a number looks bad, and when to ignore the number entirely.
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Download free on the App StoreWhat we write about
One body. Five perspectives.
Sleep
Sleep stages, recovery and why quality counts for more than raw duration.
7 posts
Training
Load, recovery and how to place sessions around your daily readiness.
16 posts
Everyday
Shift work, stress and routines that fit into a day that is already full.
10 posts
Community
Fair challenges, teams and motivation that respect different starting points.
6 posts