1. What is Critical Swim Speed (CSS)?

Definition: CSS is a swimming metric that estimates a swimmer's aerobic endurance speed, similar to lactate threshold in running.

Purpose: It helps swimmers and coaches monitor training intensity and aerobic fitness improvements.

2. How Does the CSS Calculation Work?

The calculator uses the formula:

Where:

• \( CSS \) — Critical Swim Speed (meters/second)
• \( D2 \) — Longer distance (typically 400m)
• \( D1 \) — Shorter distance (typically 200m)
• \( T2 \) — Time for longer distance (seconds)
• \( T1 \) — Time for shorter distance (seconds)

Explanation: The formula calculates the slope between two swim efforts, representing the swimmer's sustainable speed.

3. Importance of CSS in Swimming

Details: CSS is used to:

• Set appropriate training zones
• Track aerobic fitness progress
• Prescribe interval training paces
• Predict race performance

4. Using the Calculator

Tips:

• Enter distances in meters (default 200m and 400m)
• Enter times in seconds (e.g., 120 for 2 minutes)
• D2 must be greater than D1
• T2 must be greater than T1

5. Frequently Asked Questions (FAQ)

Q1: Why use 200m and 400m distances?
A: These distances are standard for CSS testing as they provide a good balance between anaerobic and aerobic contributions.

Q2: What's a good CSS value?
A: CSS varies by swimmer level. Competitive swimmers typically range 1.2-1.8 m/s, while beginners may be 0.8-1.1 m/s.

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

Q4: Can I use different distances?
A: Yes, but the standard 200m/400m provides the most reliable results. If using different distances, maintain at least a 2:1 ratio.

Q5: How does CSS relate to race pace?
A: CSS typically corresponds to paces for events between 1500m-5000m in pool or open water swimming.