Calculator · Swim

EBT-2: Stroke tipping points.

5 × 50 m at varying speeds · SR vs pace plot

Battery test #2 of two. Five timed 50 m efforts at varying speeds, from cruise to flat-out. We plot your stroke rate against your pace, so you can see exactly where your DPS collapses or your stroke rate plateaus. The two reference lines define the “balanced” band; deviations above or below are technique tells.

Use the calculator ↓ How to read the curve

Plug in 5 timed 50s

Swim five 50 m efforts at different speeds, e.g. cruise, easy, moderate, hard, all-out. Each lap: time (30–60 s), stroke rate (or stroke count + we’ll auto-compute SR). Hit calculate to plot your curve against the reference band.

Units

How to read the curve

Three regions, three different stories.

Below the SR-too-low line

You’re under-rating at that pace, coasting on big DPS but with a stroke rate too slow to support faster pace. Add tempo work; raise SR without dropping DPS.

In the band

Balanced. Your stroke rate matches the pace appropriately for the population. Aim to shift the entire curve faster in the next training block, same balance, higher speeds.

Above the DPS-collapse line

You’re thrashing, high SR but DPS has cratered. Common at the fast end of the test (lap 5). The pace where your line crosses up = your tipping point. Past it, more SR doesn’t buy speed; better technique does.

The most diagnostic single point: where your curve crosses the DPS-collapse line. That’s the pace beyond which technique is the limiter, not engine. Train at and just above that pace to push the tipping point faster.

Coach note

Test protocol matters, here’s the clean version.

Bad protocol = noisy curve = useless conclusion. Five rules for a clean EBT-2:

Same lane, same pool, same time of day, or trends are meaningless.
Spread the speeds widely: e.g. 60s / 55s / 50s / 45s / 40s. Tight bunching of similar paces makes the curve uninformative.
Rest fully between efforts, 1:30–3:00 minimum, more for the fast ones. Fatigue from earlier efforts collapses DPS at later faster paces and shifts your tipping point falsely earlier.
Same stroke (free) on every lap. Don’t mix strokes, don’t change kicking effort radically across reps.
Re-test every 6–8 weeks. Look for the curve shifting right (faster paces at the same SR) or the tipping point moving faster.

Pair with EBT-1 for the static-snapshot view; this test gives the dynamic. Together they tell you exactly where to focus, technique, top-end speed, or stroke rate, in your next swim block.

On-site swim coaching EBT-1 first

Related calculators

EBT-1, Stroke efficiency

Single-snapshot DPS rating + verdict. Run this first to anchor your overall efficiency.

Open → Critical swim speed (CSS)

Pace zones for swim training. Pair with this test’s tipping point to set hard-set targets.

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Want video to pair with the curve?

On-site swim coaching with the Slipstream stationary-swim setup turns this test into a side-by-side: your EBT-2 curve next to high-speed underwater footage. We see why DPS collapses at your tipping point, and exactly what to drill.

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