How Critical Swim Speed can improve your swim times.

What is Critical Swim Speed (CSS)?

Critical Swim Speed (CSS) is a fundamental concept in swimming that refers to the fastest pace an individual can sustain continuously without becoming exhausted.

It is also known as the aerobic swimming threshold.
CSS serves as a benchmark for determining training intensities and setting performance goals. By identifying your CSS, you gain insights into your aerobic capacity and endurance level.

It helps you gauge your swimming abilities and tailor your workouts accordingly.
To determine your CSS, you typically perform a swim test, which involves swimming multiple distances at different speeds. The data collected from these timed efforts allows you to calculate your CSS pace, which represents the pace you can sustain over longer distances.

Understanding your CSS is crucial for effective training and race strategies. It helps you optimize your workouts by training at appropriate intensities, ensuring that you challenge yourself without overexertion. By focusing on maintaining your CSS, you can enhance your endurance and gradually improve your overall swimming performance.

CSS serves as a valuable tool for swimmers of all levels, from beginners to elite athletes, as it provides a foundation for structured training and helps track progress over time. It allows you to set realistic goals and work towards achieving them, ultimately enhancing your overall swimming experience.

What are the Benefits of CSS Training
​CSS swimming, performed at your maximum aerobic threshold, offers numerous benefits for your overall fitness and performance. One of the key advantages is the improvement of your aerobic capacity, which directly translates to enhanced endurance and stamina.
By consistently training at your CSS pace, you gradually push the boundaries of your aerobic system, allowing it to adapt and become more efficient. This increased aerobic capacity not only benefits your swimming but also carries over to other activities such as running and cycling. You'll find that your overall cardiovascular fitness improves, enabling you to perform better in multi-sport events like triathlons.
Another advantage of CSS training is the development of a strong pace over longer distance swims. By focusing on maintaining a steady and sustainable pace, you enhance your ability to sustain a consistent speed throughout the duration of a race or a longer training session. This skill is invaluable for open water swims or distance events where pacing plays a crucial role in achieving optimal performance.
Moreover, training at your CSS pace helps you cultivate a sense of pacing control. By becoming familiar with your sustainable pace, you gain a deeper understanding of your body's limits and capabilities. This knowledge enables you to avoid starting a race too fast, which can lead to early fatigue and compromised performance. Instead, you can strategically pace yourself, utilizing your CSS training to maintain a steady and efficient rhythm from start to finish.
In summary, CSS training allows you to build your aerobic capacity, enhancing your endurance for swimming as well as other activities. It helps you maintain a strong and sustainable pace over longer distances, contributing to improved race performance. Additionally, it cultivates a sense of pacing control, ensuring that you race smarter and maximize your potential. Embrace CSS training as a valuable tool in your swimming arsenal, and reap the rewards of improved fitness and performance.

1. Because the pace you swim at when doing CSS swimming is at your maximum aerobic threshold, you will build on your aerobic capacity  This allows you to swim and still have some reserve for other activities such as running and cycling.
2. This type of training will build your ability to maintain a strong pace over longer distance swims.
3. Because you are training at a regular pace you will be able to use this to ensure you don't go off too fast in the race.

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What do I need to do to find my CSS time.

To find your CSS time you will need to record your times for a 400m and 200m swims in the same swim session. . Enter these times into our CSS calculator on this page. Then use the calculated time in your training to improve your swim times.

Session to measure your CSS time,
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• Warm up
  • 1 x 300m relaxed front crawl swim.
  • 4 x 50m front crawl swim with 10s rest after each 50m
  • 4 x 25m sprint swim with 10s rest after each 25m
  • 1 x 100m relaxed front crawl swim
• 400m time trial
• Rest for 4 - 5 minutes making sure you have fully recovered.
• 200 time trial

• Warm Down 
  • 1 x 100 relaxed choice swim

Once you have your times, work with your coach to define suitable training sessions where you can use your CSS times to then improve that swim endurance. Remember to check your CSS times every now and then so that you can adjust sessions as you improve. Again talk with your coach to determine how regular you check the times.

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CSS Calculator