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Swim Training Zones


Critical Swim Speed (CSS) is a simple measure of pace which can be used to improve your swim fitness, plan pacing zones, and benchmark your swim levels.

CSS is the pace at which you would currently swim a 1500 Time Trial (in yards or metres). The test and measurement are an effective way to understand the pace that you will be able to race at. It is a CSS is a pace that’s tough enough to develop your aerobic capacity but not so hard that it’ll take you days to recover. Training with CSS pacing teaches you about pace awareness.

Don’t worry, to get your CSS measurement you don’t have to do a 1,500m Time Trial! The test uses two much shorter efforts swum at a very hard effort of 400 and 200 yards or meters (respectively), you can then you plug the times of each of your efforts into the calculator below and you will be given a CSS (Critical Swim Speed).

Critical Swim Speed Calculator

My 400m Time Trial Was:
My 200m Time Trial Was:

You can now enter this value into your Tridot Threshold History screen as your threshold swim pace.

Find help for doing this here.