Your SWOLF score is a rough measure of efficiency, and it’s calculated per-length as the sum of the time it took you to swim the lap, and the number of strokes it took you to swim it.

SWOLF isn’t perfect, but it’s a solid way to measure improvements in stroke efficiency over time. Sometimes it’s hard to compare stroke count and time if you swim in different pool lengths. Efficiency fixes this problem, so you can compare apples-to-apples in different pool lengths. If you sometimes swim in a 25 yard pool, and sometimes in a 50 meter pool this is what you’ll want to look at.
Interested in learning how SWOLF works and how to improve it?
Check out this week’s Whiteboard Wednesday!

Different Strokes, Different SWOLF

Each stroke carries it’s own metrics including stroke count, lap slits and SWOLF score. For freestyle and backstroke, stroke count is calculated each time an arm pulls underwater. For Breaststroke and Butterfly, a stroke cycle is completed when both arms complete a pull together. As you can see in the 4 x 50s IM set below, each stroke carries a different pair of metrics. The highlighted repetition is the 50m butterfly.

Looking at the graphs you can see this swimmer averaged :15s per 25m of butterfly taking 7 strokes on the first length and 8 strokes on the second length. The resulting SWOLF is 22 on the first 25m and 23 on the second 25m. This is very good, but remember that SWOLF is relative to your own swimming.

The Swimming Equation

ST represents total Swimming Time. This equation represents two components, the under water over time and over water time. Underwater time is made up of Underwater Time plus Turn Time. The Overwater time is a function of Cycle Count multiplied by Stroke Rate. The units for Stroke Rate is in seconds/stroke.
ST = (UT + TT) + (CC*SR)

  • ST = Swimming Time
  • UT = Underwater Time
  • TT = Turn Time
  • CC = Cycle Count
  • SR = Stroke Rate

Looking at the Metrics

Because SWOLF is a function of both Split Time and Stroke Count it’s important to monitor both as they relate to your swimming efficiency. Looking at the example set below of 6 x 50s Freestyle @ :40, you can see the second repetition of the set broken out by stroke count, split time, and the result SWOLF score.

Analyzing this set, we can see that the swimmer’s efficiency dropped on the second length of the 50m swim because the stroke count and lap split both increased. Most likely this swimmer was fatiguing through the set and you can see this with an increase in heart rate.

SWOLF Workout

Below is a very detailed analysis of a workout performed with the Apple Watch Series 3 running the MySwimPro Workout of the Day.

Read more about this workout analysis and the advanced analytics available on the MySwimPro platform here.

I hope this video was helpful in understanding how SWOLF is calculated and how you can use it as a metric to improve your swimming performance over time.
Until next time, happy swimming!


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