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Two tests to evaluate your swimming level

We explain the Critical Speed ​​and the Swolf

In this article we offer you two ways to know your level or performance in swimming. They are very easy to do and you will only need a watch with chrono to do it

We will talk about two different tests: the Critical Speed ​​and the Swolf

Critical Speed ​​(Critical Speed, CS)

The critical speed correlates with the maximum speed at which the lactate state is stable.

For this reason, with this test we will obtain the optimal swimming rhythm in the middle aerobic zone, which will allow us to work on aerobic endurance and later check if there are improvements in our performance.

To carry out the test it is necessary to carry out two distances (400 and 200 meters or 400 and 50 meters) at the maximum possible speed and with full recovery between both tests.

The time used in each distance (in seconds) must be recorded and the following formula applies:

CS = (DM-Dm) / (TM-Tm)

DM = Greater distance (400m); Dm = Less distance (200m); TM = Time in the greatest distance in seconds; Tm = Time in the shortest distance in seconds.

This is an example:

  • 400m test: 5:00 to 300 seconds
  • 200m test: 2:20 to 140 seconds
  • vcrit = (400-200) / (300-140) = 1,25 m / s
  • Time in 100m= 100/1,25 = 80s at 1'20”

This critical speed corresponds to the anaerobic threshold, that is, training at lower speeds will make us work on our aerobic energy systems and at higher speeds they will make the body's anaerobic sources work.


The swolf is a indirect measurement of swimming efficiency that you get at add the strokes made to travel a distance plus the time used for it.

But if you don't have said sports watch, all you have to do iss swim a distance (25 or 50 meters) at the maximum possible speed, counting all strokes you do and noting the time taken in seconds.

The data you obtain will be your personal reference, from which you can see your evolution and improvement over the course of training.

An example:

  • If you perform 25 meters in 20 seconds and use 20 strokes for it, your Swolf will be from 40

It is advisable to eliminate the influence of the exit and the turn, so that the test in pool of 50 meters will be more reliable. When you want to check your training progress, choose a test replication as similar as possible to the first time.

The fact of noting both the number of strokes and the time spent in a stipulated distance will allow you to analyze the evolution in a more exhaustive way, given that the Swolf can be the same but the data can not.

Another example

  • First test: Perform 50m in 40 seconds with 40 strokes à Swolf 80
  • Ssecond test: Perform 50m in 45 seconds with 35 strokes à Swolf 80

It is possible that in the second case the athlete has decreased the stroke rate by performing a greater sliding phase.

Having efficiency data and critical swim speed will help you plan your workouts in terms of technique and rhythms for the series, so get to work to improve your best records!


Wakayoshi K, Ikuta K, Yoshida T, Udo M, Moritani T, Mutoh Y, et al. (1992). Determination and validity of critical velocity as an index of swimming performance in the competitive swimmer. Eur J Appl Physiol.; 64: 153-7. Oca, A. (2013). Use of critical speed for aerobic endurance training in young swimmers. https://g-se.com/uso-de-la-velocidad-critica-para-el-entrenamiento-de-la-resistencia-aerobica-en-nadadores-jovenes-bp-Y57cfb26d6195d

Ortega Diez, J. (2015). Swolf https://g-se.com/swolf-bp-X57cfb26e81fe6

Laura García Cervantes

Laura García Cervantes
Laura Garcia Cervantes.
Dra. Science of Physical Activity and Sport

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