Swim analytics: from your activities & from a CSS test

Two layers

• From your activities (always available), recent swims, 8-week swim count and volume, average and best pace per 100 m, a 12-week weekly-volume chart, and stroke rate. Works from your uploaded swims with no test required.
• Threshold & endurance (after a CSS test), Critical Swim Speed and the Stroke Distance Index (SDI), which unlock swim pace zones.

Get the most from it

Run a short CSS test (e.g. 200/400 or 100/500) to set CSS and SDI, that turns the activity history into proper zone-based analysis. Until then the activity view (volume, pace trend, best pace) still gives a clear picture of swim fitness and consistency.

Reading pace

Open-water GPS can over- or under-measure distance, which skews pace for a single swim, the trend across many swims is more reliable than any one session. For a mis-measured swim, set the activity's distance override.

Where to go next

• Comparing & trending workouts
• Swim economy calculator