FAQ
Frequently asked questions
What is the difference between CSS zones and Swimsmooth zones?
CSS zones use 5 broad categories anchored to your critical swim speed. Swimsmooth uses 6 more granular zones defined as offsets from CSS pace (CSS-10, CSS-5, CSS, CSS+5, etc.), which many coaches find more practical for writing swim sets.
How do I test my CSS?
Swim a 400m time trial and a 200m time trial (in that order, with 5-10 min rest between). CSS = (400m distance - 200m distance) / (400m time - 200m time). Our calculator does this math for you.
How should weekly swim volume be distributed?
For triathlon, about 60% of swim volume should be at or below CSS pace (endurance), 25% at CSS pace (threshold development), and 15% above CSS (speed and race preparation).
Evidence
References
- Determination and validity of critical swimming velocity
Journal of Swimming Research
- Swim Smooth: The Complete Coaching System
Swimsmooth
This calculator provides estimates based on published exercise science research. Individual responses vary. These outputs are not a substitute for coaching, medical clearance, or your own experience. Always listen to your body and consult a qualified professional before making significant changes to your training.
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