June 15, 2021
How To Swim A Critical Swim Speed Test
A Critical Swim Speed (CSS) test helps you determine your critical swim speed and establish training zones for swimming. Here’s how to do it.
Critical Swim Speed (CSS) is to swimming what function threshold power (FTP) is to cycling, and functional threshold pace (FTPa) is to running – an approximation of your lactate threshold.
Knowing your lactate threshold is essential for tracking your progress as an athlete and for determining training zones that are accurate for you.
If you’re interested in improving your swimming, knowing your CSS could significantly help you.
Factors To Consider Before Your Test
Before deciding when to swim your CSS test, you need to consider certain factors to maximise your test and get the most reliable result to establish your training zones.
Below are the factors that you have control over and that can influence your test. Please consider each carefully and aim to keep things as consistent as possible between tests.
Pool Length
You can swim the test in a 20m, 25m, 33.3m or 50m pool. For accuracy between tests, it’s best to swim the tests in the same length pool.
Physical Condition
The CSS test is challenging because you have to swim hard. Do not attempt this test if you are ill or suffering from any form of niggle. You want to be in good condition when you swim this test.
Time Of Day
To keep things consistent between tests, we recommend you complete your CSS test at the same time of day each time you test. If you do swim at a different time, note it in your training log for future reference.
Pre-Hydration
Make sure you adequately hydrate before your test. If you are conducting the test in the morning, you will wake from sleep dehydrated. Preload with sodium (300-500mg) to assist your cardiovascular system 30-minutes before you start. The same applies if you test late in the evening. Hydrate well throughout the day and preload with added sodium 30-minutes before you start your swim.
Cut Race Times, Not Corners.
Racing at your potential and enjoying training is easy when you’re following the right programme.
How To Determine Your Critical Swim Speed
You can determine CSS by swimming an intense but straightforward field test in the pool.
To do that, follow the steps below …
- Perform a thorough warmup, progressively bringing your heart rate up.
- Swim 400m as hard as you can and capture your time. Your goal is to swim at the maximum pace you can sustain for 400m.
- Take 5 to 10 minutes to recover, swimming some very easy laps to help flush waste products from your muscles.
- Next, swim 200m as hard as you can and capture your time. Again, your goal is to swim at the maximum pace you can sustain for 200m.
- Check that you swam the 200m at a faster time per 100m than the 400m. This should always be the case because it’s a shorter distance. This is essential or the calculation will not work!
- End with an Easy swim to cool down properly. We also recommend you do some light stretching to aid in recovery.
What Now?
With your 400m and 200m times now known, you need to calculate your CSS pace. To do that, use our CSS calculator.
Enter your times, and we’ll calculate your CSS pace and training zones.
When To Test Again
Swimming is a low impact sport, so you can test your CSS quite frequently.
Testing every 4 – 6-weeks is a good guideline, although you should not be dogmatic and should set your testing schedule to suit your goals and current physical condition.
Enjoy!
Ben Pulham