Swim Smooth didn't invent the concept of Critical Swim Speed (CSS) but we like to think we had a lot to do with making it popular. CSS training helps you determine your fitness level and set your training paces so you get the biggest fitness gains for distance swimming (e.g. triathlon and open water races).
The CSS Test
The first thing to do is to swim the CSS test consisting of a 400m/yd timetrial and then a 200m/yd time trial. You can enter the results on the CSS calculator on our website here:
Or use the more sophisticated version in the Swim Smooth Guru here:
The calculator spits out your CSS pace per 100m - which should be roughly the speed that you can sustain for a 1500m timetrial. From there you can set your pace in different training sessions, ideally programmed in a Finis Tempo Trainer Pro for maximum accuracy and feedback as you swim.
If you repeat the test you can also track your progress over time, for example: (kudos to Dan H for this great improvement from 1:55 to 1:33 / 100m over the last year):
|Much kudos to Dan for this great improvement from 1:55 to 1:33 / 100m over the last year|
However... one problem with the CSS test is that it is very sensitive to your 200 and 400 times, and requires you to swim two well paced timetrials that are representative of your current fitness. Fatigue from other training sessions can play a role and if you're not an experienced swimmer it can be easy to start to fast and then blow-up, or start too slowly and underperform. If something like that goes wrong, your 200 and 400 times will be off and the calculator will give you an inaccurate CSS pace.
Validating Your CSS Test Result
4x 400m at CSS pace + 6 sec /100m
3x 400m at CSS pace + 5 sec /100m
2x 400m at CSS pace + 4 sec /100m
1x 400m at CSS pace + 3 sec /100m
Or if you're not quite up to that yet, swim this as 10x 300m instead - known as "Pink Mist"!
If you find that session hard but do-able then you know your CSS pace is accurate. But if it's way too hard or too easy then you can adjust your CSS pace slower or faster to compensate. We call this process "tweaking" and we have bespoke tool for it within the Guru (Pro subscription required):
Then repeat the Red/Pink mist session again a week later to see how it feels.
With a little experience it's quite easy to judge where your CSS pace is and tweak it up or down as you go along. You can do this yourself but the Guru makes it very easy and allows you to track your progress over time, showing you exactly how and when you've improved - which is hugely motivating:
So the next time you swim the CSS test, validate it using a longer session such as Red Mist and be confident you're at the right starting point to take your swimming forwards.