The Capacity Check
Is your body keeping up with what you're asking of it?
Ten minutes, four signals, and no tests. You already own the data.
Before you start
The gap between coping and keeping up.
There's usually a gap between how well you think you're coping and how well your body is coping. It can stay open for a year before anything obvious goes wrong. What people notice first is being tired, or work feeling harder than it used to, and neither is specific enough to act on.
Most people open the app, read the score on the front screen, decide it was a good night or a bad one, and get on with the day. That score summarises several things worth reading separately, which is why it can look fine on a night your sleep was broken.
What follows is four signals that between them answer one question.
Is your body keeping up with what you're asking of it, or quietly falling behind?
Three are already on your wrist. The fourth is your working week. Each one tells you what to look at and what counts as a yes, so keep score as you go.
None of this is a diagnosis or advice about your situation. It's a way of finding out whether there's a question worth asking properly.
Signal one
Your HRV trend, read against your resting heart rate.
Heart rate variability is the most tracked metric on most wearables. It's also the most misread.
Most people take the morning number as a readiness score. High means push, low means go easy. It carries more than that: HRV reflects your nervous system's ability to restore itself between bouts of load, the balance between the accelerator and the brake.
A single low reading is usually noise. A declining trend across several weeks is a signal, and it means the system is spending more time accelerating than braking.
Check yourself.
Open your app and look at HRV across the last four to six weeks. Ignore individual days, look at the direction, then look at resting heart rate over the same period.
A declining HRV trend alongside a rising resting heart rate is stronger than either on its own. The two say the same thing from opposite directions: you're spending more than you're putting back, for long enough that both have moved. Most people never look at them together.
This counts if both are moving.
HRV trending down and resting heart rate trending up, across four to six weeks. One moving on its own is worth noting and doesn't count.
Signal two
Your deep sleep, not your sleep score.
Most leaders don't have insomnia. They have fragmented deep sleep, and those aren't the same problem.
You can sleep a solid eight hours and still carry deficits close to a bad insomniac's. What matters is how the sleep was organised, not how long it lasted.
Deep sleep is the stage that does the repair, and your tracker may call it slow wave sleep. It's when your brain consolidates memory and restores hormone regulation. Sustained load raises cortisol, flattens its daily rhythm, and breaks that sleep up.
Some people feel tired with it and plenty don't, which is what makes it hard to catch. What it reliably does is erode four things.
Check yourself.
Ignore the composite sleep score. Open the stages view and look at two things across a fortnight: how much deep sleep you get, and how consistent it is night to night.
Most healthy adults get between about an hour and an hour and three quarters a night, falling with age. Treat that as orientation rather than a target: trackers know you were asleep and are much less reliable at staging which sleep you were in. Your own figures against each other beat yours against anyone else's.
This counts if your deep sleep has dropped, or swings hard.
Lower across the last fortnight than the same stretch three months ago, or swinging by more than about half between your best and worst nights. If you've no history to compare against, count it if more than a third of your nights come in under about forty-five minutes.
Signal three
The five things you notice at work and put down to a busy period.
The physiology shows up in behaviour before anywhere else, as five specific things you can count.
Check yourself.
For one week, keep a tally. At the end of each day, note which of these happened.
Five ticks a day at most, thirty seconds before bed. Write it down as you go, because nobody remembers this accurately by Sunday.
This counts if three or more showed up on most days.
Three of the five, on more days than not, across the week.
Signal four
Whether your last break actually restored you.
There are two ways to know whether a break restored you: ask how you feel, or look at what your physiology did. You want to see whether those agree, because feeling recovered and having recovered are different things, and only one leaves a trace in the data.
Check yourself.
Find your last real break. Look at HRV and resting heart rate for the week before, the week during, and the two weeks after. A break that restored you shows a shift that holds. One that only felt good dips back within days, or never moves.
This counts if the break left no trace.
A week or more away produced no change in the two numbers, or the change had gone within days of getting back.
Now count
Add up how many of the four counted.
The important part
What this cannot tell you.
A declining trend is a signal, not a diagnosis. Acting on it without knowing what's behind it means guessing at which of six things to change.
Sometimes the answer is obvious. Sleep more, train less, drink less, carry less. Sometimes that's all it is.
Often it isn't. The same pattern comes from metabolic dysfunction, hormonal disruption and chronic dysregulation of the stress axis, and those three look identical on a wrist. They need different things done about them, and two won't improve however much you rest.
Your wearable gives you the signal. It can't tell you what's driving it.
What answers it
Where to take it from here.
There's a short guide at the foot of this page covering the six causes and which is most likely to be yours. It costs nothing, and for a lot of people it's enough to be going on with.
If you would rather have experienced eyes on it, one appointment answers the question properly.
From Signal to Cause.
What a declining pattern actually points to: the six things that produce it, and which you can assess without anyone taking blood.
And if you'd rather just ask
Twenty minutes on the phone, at no cost.
I'm Ben Ingram. I'm an NHS GP partner in Kent and I run a small private practice alongside it, where this is most of what I do.
Tell me what your numbers are doing and I'll tell you straight whether it's worth looking into properly. If it isn't, I'll say so and we stop there.