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.
There's usually a gap between how well you think you're coping and how well your body is actually coping. It can run for a year or more before anything obvious happens. What people notice first is being tired, or work feeling harder than it used to, or both, and none of that is specific enough to act on.
You can close most of that gap in ten minutes, with data already sitting in your phone.
Most people have a wearable now. They open the app, look at whatever score it puts on the front screen, decide it was a good night or a bad one, and get on with the day. That score is a summary of 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 about your working week.
Each one tells you what to look at, what it means, and what counts as a yes. Keep score as you go, because two signals moving together means something different from one moving on its own.
None of this is a diagnosis and none of it is advice about your situation. It's a way of finding out whether there's a question here 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 check the morning number and take it as a readiness score. High means push, low means go easy, and it carries more than that. HRV reflects your autonomic nervous system's ability to restore itself between bouts of load, which is 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 your HRV across the last four to six weeks. Ignore individual days and look at the direction. Then look at your resting heart rate over exactly the same period.
A declining HRV trend alongside a rising resting heart rate is a stronger signal than either on its own. The two say the same thing from opposite directions. You're spending more than you're putting back, and it's been going on long enough that both measures have moved. Most people never look at the two 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 seven or eight hours and still carry deficits close to a bad insomniac's, because what matters is how the sleep was organised rather than how long it lasted. Slow wave sleep is when your brain consolidates memory, restores hormone regulation and recovers, and 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 part of what makes it hard to catch. What it reliably does is erode things slowly: working memory, emotional control, decision quality, and how well you absorb a hard training session.
Check yourself. Ignore the composite sleep score, which is a number the manufacturer invented. Open the stages view and look at two things across a fortnight: how much deep sleep you're getting, and how consistent it is night to night.
Most healthy adults get somewhere between about an hour and an hour and three quarters a night, falling with age. Treat that as orientation, not a target, because trackers are good at knowing you were asleep and much less reliable at staging which sleep you were in. Deep sleep is the stage they get most wrong. Your own figures compared against each other are more reliable than yours compared 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 it shows up anywhere else, and it arrives as five specific things you can count.
For one week, keep a tally. At the end of each day, note which of these happened.
- You lost your threadYou lost track of what you were about to say.
- Something small got bigA frustration escalated faster than it should have.
- An easy call felt hardA decision that ought to have been straightforward felt effortful.
- You moved too fastYou made a call faster than you normally would.
- You stopped being curiousYou noticed you were less interested in the other side of an argument than usual.
Five ticks a day at most, about thirty seconds before bed. Write it down as you go, because this is exactly the sort of thing nobody remembers 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. What you want is to see whether those two agree, because feeling recovered and having recovered are different things, and only one of them 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 once you're back. A break that only felt good dips back to baseline within days, or never moves at all.
This counts if the break left no trace.
A week or more away produced no change in the two numbers, or whatever change there was had gone within a few days of getting back.
Now count
Add up how many of the four counted.
- NoneGood, and worth writing down. Note where your four numbers sit today so you have a baseline, because the value is in the comparison and not in any single reading. Run it again in three months, and each quarter after that.
- OneWorth watching, unless it's signal one, the HRV and resting heart rate pair. Look again in a month.
- Two or moreThat's a pattern, not a bad month, and patterns have causes. This is the point where it's worth understanding instead of pushing through.
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, from hormonal disruption, and from chronic dysregulation of the stress axis, and those three look identical on a wrist. They need different things done about them, and two of them won't improve however much you rest.
Your wearable gives you the signal. It can't tell you what's driving it.
From Signal to Cause.
I've written up what a declining pattern actually points to: the six things that produce it, in the order I'd work through them, and which of them can be sorted out without anyone taking blood. I'll send it to you now.
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.