Most testing in swimming answers one question at a time. How fast is the swimmer? How fit? How's the start? Each test sits in its own corner, its result jotted on a whiteboard, and the coach is left to stitch the corners together by instinct.
We run nine tests. But they aren't nine separate answers. They're three questions asked about the same athlete — and the value isn't in any single number, it's in what happens when you read them together.
Here's why we test what we test, and what each one feeds once it's in the system.
Question one: is the engine adapting?
The first cluster is about physiology — whether the work the athlete is putting in is actually changing what their body can do.
The 7×200 step test is the centrepiece. Swum as a descending set with heart rate recorded after every rep, it maps the athlete's heart-rate-to-velocity curve — and the thing we're watching for is the curve shifting rightward over a training block, where the swimmer holds more velocity for the same heart rate. That shift is one of the cleaner signals of improving aerobic fitness there is, and it's what lets the app set genuinely individual training zones instead of generic percentages. One honest caveat: heart rate is pushed around by heat, hydration, sleep, caffeine and nerves, so a single test is a data point, not a verdict — it's the trend across tests that means something.
The 6×50 lactate set asks a narrower question: can the athlete hold pace when it gets ugly? Swum at 200m race pace, the drop-off between the fastest and slowest rep is a practical window into fatigue resistance — into whether the swimmer can defend backend speed as the metabolic cost climbs. A small drop-off says fatigue resistance is strong. A large one tells the app to prescribe more threshold work, and tells the coach exactly why.
Individually, each is a useful data point. Together, they describe an engine: its ceiling, its efficiency, and whether it's trending the right way. The app tracks both across time, so the question stops being "how did she test today" and becomes "is the training actually working."
Question two: is the chassis efficient?
The fastest engine in the world is wasted if the hull it's pushing leaks speed. The second cluster is about mechanics — how efficiently the athlete converts effort into forward motion.
The V-Stroke profile is the sharp one. Building from 70% to a full race-pace 100% effort while counting strokes, it exposes the athlete's efficiency ceiling — the point where, in the scramble for more speed, stroke count balloons and technique falls apart. A swimmer whose efficiency holds at race pace is a swimmer whose speed is real. One whose stroke count spikes under full effort is buying pace with mechanics they can't sustain, and the app flags that as technique-under-fatigue work, not more conditioning.
Around it sit the propulsion-balance tests. The 25m sprint kick isolates what the legs contribute. The 100m pull isolates the upper body. Read against each other and against a full swim, they give a pull-to-kick picture — a map, tracked within the swimmer over time, of where their propulsion actually comes from and where it's over-reliant. A swimmer leaning too hard on the pull with a weak kick gets a specific volume prescription, not a vague "work on your kick."
And the start gets its own pair. The 10m fly velocity measures peak underwater output; the 15m dive measures the whole start sequence from the block. Compared against each other, they separate the underwater phase from the reaction and flight — so when a start is slow, the app can tell the coach which part is slow, which is the difference between fixable and guessable.
None of these is a fitness test. They're efficiency tests — and efficiency is where races are quietly won and lost while everyone's watching the pace clock.
Question three: is the nervous system ready?
This is the cluster most testing ignores entirely, and the one we think matters most.
An athlete can have a well-tuned engine and an efficient chassis and still have a bad day — because they aren't primed to fire all of it. The third cluster reads readiness directly, before the session, so the coach knows what kind of work the athlete can actually express today.
Grip strength, taken cold before warm-up, is a cheap daily trend marker. We're honest about what it is and isn't: the evidence that grip reflects whole-body or central fatigue is limited and mixed, so we don't treat it as a precise readout of "CNS state." What it is good for is cheapness and consistency — a sustained drop against a swimmer's own rolling baseline is worth a second look before you load them, calibrated to that individual's normal variation rather than a one-size number.
The CMJ jump, measured against a Monday baseline, is the better-validated of the two — countermovement jump is one of the most established field markers of neuromuscular readiness there is. We flag a drop of more than 10% against baseline, and we pick 10% deliberately: day-to-day jump variation is usually around 5%, so a 10% fall sits clearly outside the noise. It's a conservative threshold — it catches real fatigue rather than chasing every small wobble — and when it trips, the app steers the day toward aerobic or technique work instead of sprint and power.
Together these let a coach stop guessing whether today is a load day or a back-off day — with the information arriving before the decision, not after the times disappoint.
Why they only work together
Here's the part the list format hides. The power isn't in the nine tests. It's in the relationships between them.
A slow 100m means one thing if the engine tests are strong and the readiness tests are flat — that's a readiness problem, train light and it'll come back. It means something completely different if the efficiency ceiling has collapsed — that's a mechanics problem, and more conditioning will make it worse. The same disappointing time has opposite causes, and the only way to tell them apart is to read the clusters against each other.
That's what the app is for. Not to store nine numbers in nine boxes, but to hold them in relationship — so when a swimmer is off, the system can point at why, and the coach can act on cause instead of symptom. Nine tests feeding three questions feeding one picture of the athlete.
One honest note that runs through all of it: these readiness markers are signals, not verdicts — best read as trends across weeks rather than single-day final words, and always alongside a coach's own judgement rather than in place of it. Used that way, they turn a wall of disconnected numbers into something you can actually coach from.
This is the engine room of what we've built. If you'd like to see the full battery feeding a single picture of each swimmer, join the founders list.