Critical Swim Speed (CSS) is an effective tool to measure swimming speed improvement over time and predict time to complete larger distances.

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Critical Swim Speed estimates the pace per 100 that you would maintain during a maximal 1500 metre time trial.
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It’s calculated by comparing your 200m time trial to your 400m time trial.

Enter Your Time For 400 (metres or yards)
Enter Your Time For 200 (metres or yards)
Your CSS Pace Is: /100

Update your swim speed training zones

Remember to update your Threshold Swim Pace in TrainingPeaks and review your new Swim Speed Training Zones.

Go to your settings, and ‘Zones’.
 Under ‘Speed/Pace’, Add or Edit your ‘Swim Pace’, using ‘Threshold Speed’, Select ‘MyProCoach Swimming’ for the zones. This will give you your training paces as below:

Zone 1 – Easy
Zone 2 – Steady
Zone 3 – Moderate
Zone 4 – Hard
Zone 5 – Very Hard

CSS Sample Workouts

Once you’ve worked out your CSS pace, the training possibilities are endless. You could start off by trying these four simple workouts. You can shorten them if you’re not quite ready for 2000 meters yet. Don’t forget to include a warm-up (400m) and warm down (100 to 200m) too.

  • 20×100m with 15-second recoveries. All at CSS
  • 10×200m with 20-second recoveries. All at CSS
  • 5×400m with 30-second recoveries. All at CSS
  • 3×600m with 45-second recoveries. All at CSS

In addition to CSS training, it’s also important to strike a balance between speed, threshold, and endurance workouts in order to meet the needs of your target races. Technique work and open water training are equally important too!

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