17/09/2026
Measure your swim effort.
There are several ways to monitor your training intensity:
• Critical Swim Speed (CSS)
• Heart rate
• Rate of Perceived Exertion (RPE)
For triathlon training, my preferred method is CSS.
To find your CSS, swim a 400m time trial, recover fully, then swim a 200m time trial. Enter both times into an online CSS calculator.
Your result gives you a target pace per 100m.
For example, with a CSS pace of 1:40 per 100m:
10 × 100m every 2 minutes
Aim to finish each 100m in 1:40
Rest for the remaining 20 seconds
Simple, measurable and repeatable.
What is your CSS pace?