After completing 9 weeks of a 10-week transition to Ironman training program that I created on TrainingPeaks, I am now entering the crucial 10th week. This test week is designed to measure my progress and establish a baseline for my upcoming Ironman-specific program, also available on TrainingPeaks. The first test in this pivotal week was the Critical Swim Speed (CSS) set, which is the focus of this blog article. Join me as I delve into the details of the CSS test, its execution, and its significance for Ironman athletes.

What is the CSS Test Set?

The Critical Swim Speed (CSS) test is a method used to determine the fastest pace a swimmer can maintain continuously without exhaustion. It is an approximation of your lactate threshold speed, which is crucial for distance swimmers, triathletes, and Ironman athletes. The CSS test helps in setting training intensities and monitoring progress over time.

How is the CSS Test Set Performed?

To perform the CSS test, follow these steps:

Warm-Up: Start with a 300m easy freestyle, followed by 200m with fins (50m choice drill, 50m freestyle). Then, do 4 x 50m freestyle (25m fast + 25m easy) with 10 seconds rest, and 4 x 100m freestyle at a pace you can sustain for a 400m time trial with 20 seconds rest.
Main Set: Swim a 400m time trial as fast as you can. After a 5-8 minute easy swim/stretching recovery, swim a 200m time trial as fast as you can.
Cool Down: Finish with 100m easy choice of stroke.

Record your times for both the 400m and 200m swims. Use the CSS calculator to determine your CSS pace.

Why is the CSS Test Set Important for Ironman Athletes?

For Ironman athletes, the CSS test is invaluable because it helps in:

Pacing: Knowing your CSS pace allows you to train at the right intensity, ensuring you can sustain your speed over long distances without burning out.
Efficiency: Training at your CSS pace improves your aerobic capacity, making you a more efficient swimmer. This is crucial for conserving energy for the bike and run segments of an Ironman.
Progress Tracking: Regular CSS testing helps you monitor improvements in your swim fitness and adjust your training accordingly.

Mechanism of the Set and How to Do It for Maximum Performance Gains

The CSS test works by measuring your speed over two distances (400m and 200m) and calculating the pace you can maintain without exhaustion. This pace is used to set training intensities that improve your aerobic capacity and endurance.

How to Perform the CSS Test:

Consistency: Perform the test in the same pool and under similar conditions each time to ensure accuracy.
Hydration and Nutrition: Ensure you are well-hydrated and have adequate nutrition before the test.
Recovery: Allow sufficient recovery between the 400m and 200m time trials to ensure accurate results.

Frequency: Conduct the CSS test every 6-8 weeks to track progress and adjust your training zones. This regular testing helps in fine-tuning your training plan and maximizing performance gains.

By incorporating the CSS test into your training regimen, you can optimize your swim performance and ensure you are well-prepared for the demands of an Ironman.

Click on the following link to see me explaining the CSS on my Mind Over Matter YouTube channel.

Thanks for reading/watching.

Sean