12 × 25 m test
Twelve maximal 25 m repetitions in the swimmer’s main stroke, with 5 seconds of recovery between repetitions. Record each repetition time in seconds.
Keep the protocol consistent
Use a long-course pool and three kicks off the wall. Record any changes to the start, underwater phase, recovery or timing method before comparing assessments.
Metric definitions
Peak Speed (m/s)
The highest repetition velocity, calculated as 25 divided by the repetition time.
Critical Speed (m/s)
The mean of the two lowest velocities in repetitions 9–12. This is the operational definition for this test, not an independent estimate from a distance–time model.
Speed decrement (%)
(Peak Speed − Critical Speed) / Peak Speed × 100.
D′ (m)
Signed area above Critical Speed over active swimming time: a rectangle for repetition 1, followed by trapezoids between successive velocities. Recovery is excluded and negative areas are retained. This carries forward the later HPP numerical method, not the earlier exponential fit.
Stroke efficiency index
Velocity × distance per stroke. Recorded stroke count is preferred (distance per stroke = 25 / count); stroke rate is the fallback (distance per stroke = velocity / (rate / 60)). Missing mechanics are left blank.
Relative speed
Peak or Critical Speed divided by 100 m long-course PB velocity, expressed as a percentage.
Imported results
Existing CV, Dprime and stroke efficiency values are retained when supplied. Reports label imported CV and D′ explicitly.
Reference profile
The existing HPP sex-and-stroke reference table is used without age adjustment. Percentiles are not applied to para swimmers. A higher speed-decrement percentile means greater decrement, not better performance.
Estimated training pace
SCM velocity = 0.8518 × Critical Speed + 0.0925; LCM velocity = 0.9554 × SCM velocity − 0.0091. Pace is 100 divided by velocity. These empirical conversions are estimates.
Mean Speed (m/s)
The arithmetic mean of the twelve repetition velocities.
Interpretation
Read the metrics alongside the repetition profile and the swimmer’s history. A single assessment does not determine event suitability or prescribe training. Compare like-for-like protocols and strokes.