1. What is Critical Swim Speed (CSS)?

Definition: CSS is a swimming metric that estimates the highest speed a swimmer can maintain continuously without exhaustion.

Purpose: It helps swimmers and coaches determine optimal training intensities and monitor performance improvements.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( CSS \) — Critical Swim Speed (meters/second)
• \( T_{400} \) — Time to swim 400 meters (seconds)
• \( T_{200} \) — Time to swim 200 meters (seconds)

Explanation: The difference in distance (200m) is divided by the difference in time between the two swims to determine sustainable speed.

3. Importance of Critical Swim Speed

Details: CSS is a valuable metric for:

• Setting appropriate training zones
• Tracking performance progress
• Designing effective interval training
• Pacing strategy for races

4. Using the Calculator

Tips:

• Enter your best recent 400m and 200m times in seconds
• Times should be from maximal effort swims
• The 400m time must be longer than the 200m time

5. Frequently Asked Questions (FAQ)

Q1: Why use 400m and 200m distances?
A: These distances provide a good balance between aerobic and anaerobic contributions, making CSS a reliable endurance measure.

Q2: What's a good CSS value?

• Beginners: 0.9-1.1 m/s
• Intermediate: 1.1-1.3 m/s
• Advanced: 1.3-1.5 m/s
• Elite: 1.5+ m/s

Q3: How often should I test my CSS?
A: Every 4-6 weeks to monitor progress and adjust training intensities.

Q4: Can I use other distances?
A: Yes, some versions use 50m and 400m, but the 200m/400m combination is most common.

Q5: How should I use my CSS in training?
A: CSS pace is often used for threshold training sets (e.g., 10×100m at CSS pace with short rest).