How to measure your CSS pace
A CSS pace test means swimming flat out, you need to get your body ready for gunning it! To prepare for swimming at a fast pace, make sure to warm up properly in the pool. I wouldn’t recommend jumping strauight in and trying this without a warm up.
1. Begin with a 400m time trial, starting from a push (not a dive), and note down your time in minutes and seconds. The more accurate the better.
After this make sure you take sufficient rest or recovery after the 400m trial to fully recover and be prepared for a maximum effort in a 200m time trial. I recommend a 5 minute easy swim ideally breast stroke to relax your body before the second set.
2. Swim a 200m time trial, starting from a push (not a dive), and record your time. Again flat out maximum effort to drain the tank.
Calculating your CSS pace
Having completed the two swim sets you can use your times to calculate your CSS.
Enter your 400m and 200m times below.
What is Critical Swim Speed (CSS)?
Critical Swim Speed is the estimated pace you are capable of doing for 1500m or longer swim. It is considered to be your aerobic swimming threshold and a good benchmark to guage the pace of your swim when training for distance. It is very useful for anyone training for an Ironman.
The pace calculated should be sustainable for a prolonged period of time. From a physiological point of view, it is a speed you can travel at where your lactate production is equal to your body’s ability to dispose of lactate.
