Critical Swim Speed Test

Critical Swim Speed Test

The Critical Swim Speed (CSS) test, devised by Ginne in 1993, can be used to monitor the athlete’s aerobic capacity. The result of the test can also be used to determine the appropriate target time for each repetition of a swimmer’s aerobic training session. CSS is defined as “the maximum swimming speed that can theoretically be maintained continuously without exhaustion” just below the swimmer’s lactate threshold.

Required resources
To undertake the CSS test you will require:
  • Swimming pool
  • Stop watch
  • Assistant.
Test process
The following protocol should be followed:
  • Start each swim from a push start – not a dive in
  • Allow a full recovery between each swim
  • Record the time for each swim in seconds
  • Calculate the athlete’s CSS.
How to conduct the test
The test comprises of two maximal swims over 400 metres and 50 metres. A suitable rest period should be taken between each swim to allow the athlete to fully recover. The assistant should record the times for each swim.

Critical Swim Speed Test
Analysis of the result is by comparing it with the results of previous tests. It is expected that, with appropriate training between each test, the analysis would indicate an improvement.
Calculation of CSS
The calculation of the swimmer’s CSS, based on their 400m and 50m times,
and is as follows: CSS= (D2-D1)/(T2-T1)

Where D1 = 50, D2 = 400, T1 = time for 50m in seconds and T2 = time for 400m in seconds.
A swimmer completes a 50m swim in 31 seconds and a 400m swim in 291

  • CSS = (400-50)/ (291-31)
  • CSS = 350/260
  • CSS – 1.35 m/second.

Use of CSS to set training times
The calculated CSS can be used to determine training times for an aerobic training session.
Training session is 6 x 400m. The time per 400m repetition can be calculated
as follows:

  • Time per 400m repetition = Distance / CSS.

For an athlete with a CSS of 1.35 then the 400m repetition time would be:

  • 400 / 1.35 = 296.3 seconds = 4 minutes 56.3 seconds.

Target group
This test is suitable for swimmers but not for individuals where the test would be contraindicated.

Reliability would depend upon how strict the test is conducted and the individual’s level of motivation to perform the test.

There are no published tables to relate results to potential performance in competition.


  1. Ginne, E. (1993), “The application of the critical power test to swimming and swim training programmes”
  2. Wakayoshi, K. et al (1991) “Determination and validity of critical velocity as an index of swimming performance in the competitive swimmer”, European Journal of Applied Physiology, 64, 153-157
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