Your Data Is in Search of a Problem

Are we using data to train, or training to make data?

Matt Leu, M.S. Kinesiology | Personal Trainer Since 2006 | Studio Owner & Operator

We collect more information about ourselves than any generation before us. Steps, sleep scores, readiness, body fat, resting heart rate, calories in and out. Most of it arrives without anyone asking for it, none of it comes with instructions, and at some point it stops being information about us and starts being us.

So here's where we start when a client brings us a number.

A measurement means nothing until a question gives it a job. That's how it works in research: a question first, then the measurement chosen because it can answer that question, then a decision that changes based on what it said. Question first, instrument second.

A number without a question will always find a problem. Deviation is what these tools are built to report. Every reading is above or below something, so there is always something to notice, and noticing feels like doing.

The test is simple: name the decision the number could change. If you can name it, the measurement is earning its place. If you can't, it's decoration.

Below is how we apply that to the tools people actually use.

Body composition scans

Most consumer and gym scans use bioelectrical impedance. The machine sends a small current through you, measures how easily it passes (mostly a function of your water), and estimates the rest from your height, weight, age and sex. DEXA and the old dunk tank work differently but are still estimating, not measuring fat directly. Every method is a model.

Great for:

• Setting a safe weight loss target, so the goal protects the muscle you have

• Tracking direction over months, which scale weight alone can't do

• Giving a starting point when the goal is a body composition change rather than a number on the scale

Matters more when:

• You repeat it under identical conditions: fasted, no exercise since yesterday, no alcohol, bathroom first, no lotion, same time of day

• You're looking at a trend across six to eight weeks or more, not a single reading

• There's an actual decision attached, like how aggressive a deficit should be

Probably skip it if:

• You can't control the prep conditions, in which case you're measuring your Tuesday, not your body

• You're chasing a category label. "Athlete," "fitness," "acceptable" are words somebody attached to ranges on a chart, not physiological states. If the word is the goal, the chart handed you a problem

One thing worth knowing: the number in the biggest font on the printout is the one thing the machine never touched. Consistency in how you test matters more than the precision of the device.

Heart rate

A real biometric, not an estimate of one, and one of the few numbers here we'll actively encourage. Paired with RPE (how hard it feels, one to ten), it teaches you what your own effort actually feels like. You think you're at a 7, the monitor disagrees, and you've learned something that transfers to every session after.

Great for:

• Steady cardio where holding an intensity is the point

• Calibrating your own sense of effort against a real number

• Confirming your easy days are actually easy

• Watching aerobic fitness improve, the same work at a lower heart rate

Matters more when:

• You know your own threshold or near-max from a test rather than a formula

• You're building an aerobic base, where going too hard defeats the session

• You're returning from illness or time off and your effort perception is unreliable

• You're training in heat or unusual conditions, where the same pace costs more

Probably skip it if:

• You're mostly strength training, where heart rate is less relevant to performance

• You're doing intervals on a wrist device (see below)

• Your feel is well calibrated and watching the number takes you out of the session

One thing worth knowing: unless you've tested, your zones come from an age formula, and that formula carries a spread of about 10 to 12 beats in either direction. That's a real range of 20 or more beats between people the same age, which is a full zone, sometimes a zone and a half. The person training too hard on every easy day, never building a base, is usually doing it on a ceiling that was never theirs.

Also: the optical sensors on wrist devices read blood flow through the skin. Fine for steady cardio. They struggle with lifting and intervals, where the wrist moves, the grip is tight, and heart rate changes faster than the sensor can follow. A chest strap isn't a fancier version of the same tool. It's a different tool.

Steps and daily activity

The most useful number on most people's phones, and the one that gets the least attention because it isn't sophisticated.

Great for:

• Seeing how much you actually move on a normal day, which is usually less than people estimate

• Setting a floor rather than a target: a number you don't go below

• Noticing when life has quietly compressed your activity, a new job, an injury, a busy season

Matters more when:

• You're mostly sedentary outside of training, where daily movement is the bigger lever

• You're in a fat loss phase and total daily activity matters as much as the sessions

• You're using it as a trend across weeks rather than a daily verdict

Probably skip it if:

• Hitting the number has become its own goal and you're pacing the kitchen at 11pm

• You're already active all day for work, in which case it's counting what you already know

Sleep scores and readiness

Plenty of our clients wear rings and watches that produce a nightly score, and we're not going to tell anyone to throw one out. We would point out where it sits in the chain.

Great for:

• Noticing bedtime and wake time patterns over weeks, which most people misremember

• Confirming something you already suspect, like how much a late night or a drink costs you

Matters more when:

• You're looking at consistency of schedule rather than the nightly grade

• You pair it with how you actually feel, not instead of it

Probably skip it if:

• Checking it is changing your mood before your feet hit the floor

• You're using stage percentages to make decisions. There is no consumer intervention that targets REM or deep sleep specifically. The levers are the same either way: duration, consistency, alcohol, caffeine, light, stress

One thing worth knowing: the first question that score puts to you in the morning is one you could have answered before you picked up the phone. How do you feel? If it says you slept badly and you feel fine, you have to decide which to believe. Either way, you're the instrument doing the deciding.

And: if something is genuinely wrong with your sleep, meaning it's affecting your days across weeks and months, the answer is a physician and likely a sleep study. That's a real diagnostic with a real question behind it. The manufacturers say the same in their own materials.

Performance testing

Jump height, timed sprints, bar speed, left-right force splits. This is where the question matters most, because testing feels productive even when it isn't.

Great for:

• In-session decisions: timing a sprint set and watching for the dip tells us when quality is gone and it's time to stop

• Bar speed on a lifting day, for the same reason

• Return-to-play decisions, where a threshold has been set by someone qualified

Matters more when:

• There's a deficit we can't explain, and the test might explain it

• A decision is waiting on the result

• The test actually resembles the thing you're trying to improve

Probably skip it if:

• You're testing because the equipment is there and the number is easy to collect

• The sport already tests it. A volleyball player who wants to jump higher is at the net every day. The net will tell us in four to six weeks. A weekly test just hands him a second scoreboard to worry about during the boring weeks that produce the result

One thing worth knowing: these tests can flatline while an athlete is genuinely improving. Jump height sits still for eight weeks while the kid is reading the game better, arriving earlier, playing with more confidence. Now there's a plateau on a chart with no relationship to what's happening on the court, and a plateau demands an explanation, so somebody starts changing a program to fix a problem the test invented.

On left-right splits: some asymmetry is normal, it shifts with fatigue and terrain and intensity, and there's no established threshold where it becomes an injury risk. A 52/48 split is a Tuesday. If there's pain or performance is slipping, that's a real question worth investigating. If nobody's hurt and nothing's falling off, it's a decimal.

Blood work and clinical markers

The most legitimate measurement on this page, and the one we have the least to do with.

Great for:

• Answering questions a physician has about your health

• Catching things you cannot feel, which is exactly what the other tools on this page can't do

Matters more when:

• Ordered by someone qualified to interpret it against your history

• There's a symptom, a risk factor, or a routine screening interval behind it

Probably skip it if:

• You're ordering panels yourself to see what turns up. Wide untargeted testing on a healthy person generates findings that need chasing, and most of them lead nowhere

One thing worth knowing: this is the model the rest of these tools are imitating. A defined question, a validated measurement, a threshold, and an action. When your labs come back "within normal limits," that's the happy ending of the entire diagnostic enterprise. Nobody is disappointed by a clean panel.

What we'd have you watch instead

Frequency. Consistency. Progression.

How often you show up. Repeating activities often enough to create overlapping adaptation response and recovery. Whether the work gets harder over time on purpose rather than by accident.

Everything on this page is instrumentation around it, and those three are measurable for free: sessions on the calendar, the same lifts done well on a schedule, more weight or different positions or longer efforts than last block.

None of that produces a dashboard. It produces results, and most days it feels unremarkable while it's happening.

That's not a problem. In a clinic, unremarkable is the best news there is.

If there’s a number from a ring watch or wellness related test that you’ve taken and you're not sure what to do with it, bring it in. Sometimes it's useful and we'll build around it. Sometimes a number is just a number, and it not a problem until its a problem.